Cockroache; Ecology, behavior & history - W.J. Bell

Cockroaches

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Cockroaches 

ECOLOGY, BEHAVIOR, AND NATURAL HISTORY 

William J. Bell 

Louis M. Roth 

Christine A. Nalepa 

Foreword by 

Edward O. Wilson 

The Johns Hopkins University Press 

Baltimore

© 2007 The Johns Hopkins University Press 

All rights reserved. Published 2007 

Printed in the United States of America on acid-free paper 

9 8 7 6 5 4 3 2 1 

The Johns Hopkins University Press 

2715 North Charles Street 

Baltimore, Maryland 21218-4363 

www.press.jhu.edu 

Library of Congress Cataloging-in-Publication Data 

Bell, William J. 

Cockroaches : ecology, behavior, and natural history / William J. Bell, Louis M. Roth, Christine A. 

Nalepa ; foreword by Edward O. Wilson. 

p. cm. 

Includes bibliographical references and index. 

ISBN-13: 978-0-8018-8616-4 (hardcover : alk. paper) 

ISBN-10: 0-8018-8616-3 (hardcover : alk. paper) 

1. Cockroaches. I. Roth, Louis M. (Louis Marcus), 1918– II. Nalepa, Christine A. 

III. Title. 

QL505.5.B43 2007 

595.728—dc22 2006033232 

A catalog record for this book is available from the British Library.

To the families, friends, and colleagues of 

William J. Bell and Louis M. Roth


Contents 

Foreword, by Edward O. Wilson 

Preface xi 

ix 

ONE Shape, Color, and Size 1 

TWO Locomotion: Ground, Water, and Air 17 

THREE Habitats 37 

FOUR Diets and Foraging 61 

FIVE Microbes: The Unseen Influence 76 

SIX Mating Strategies 89 

SEVEN Reproduction 116 

EIGHT Social Behavior 131 

NINE Termites as Social Cockroaches 150 

TEN Ecological Impact 165 

Appendix 177 

Glossary 179 

References 183 

Index 225


Foreword 

Let the lowly cockroach crawl up, or, better, fly up, to its rightful place in human esteem! 

Most of us, even the entomologists in whose ranks I belong, have a stereotype of revolting 

little creatures that scatter from leftover food when you turn on the kitchen light and 

instantly disappear into inaccessible crevices. These particular cockroaches are a problem, 

and the only solution is blatticide, with spray, poison, or trap. 

I developed a better understanding when I came to realize that the house pests and 

feces-consuming sewer dwellers are only the least pleasant tip of a great blattarian biodiversity. 

My aesthetic appreciation of these insects began during one of my first excursions 

to the Suriname rainforest, where I encountered a delicate cockroach perched on 

the leaf of a shrub in the sunshine, gazing at me with large uncockroach-like eyes. When 

I came too close, it fluttered away on gaily colored wings like a butterfly. 

My general blattarian education was advanced when I traveled with Lou Roth to Costa 

Rica in 1959, and further over the decades we shared at Harvard’s Museum of Comparative 

Zoology, as he worked as a taxonomist through the great evolutionary radiation of 

the blattarian world fauna. 

This volume lays out, in detail suitable for specialists but also in language easily understood 

by naturalists, the amazing panorama of adaptations achieved by one important 

group of insects during hundreds of millions of years of evolution. Abundant in 

most terrestrial habitats of the world, cockroaches are among the principal detritivores 

(their role, for example, in our kitchens), but some species are plant eaters as well. The 

species vary enormously in size, anatomy, and behavior. They range in habitat preference 

from old-growth forests to deserts to caves. They form intricate symbioses with microorganisms. 

The full processes of their ecology, physiology, and other aspects of their biology 

have only begun to be explored. This book will provide a valuable framework for 

the research to come. 

Edward O. Wilson


Preface 

The study of roaches may lack the aesthetic values of bird-watching 

and the glamour of space flight, but nonetheless it would seem to be one 

of the more worthwhile of human activities. 

—H.E. Evans, Life on a Little Known Planet 

Most available literature on cockroaches deals with domestic pests and the half dozen or 

so other species that are easily and commonly kept in laboratories and museums. It reflects 

the extensive efforts undertaken to find chinks in the armor of problematic cockroaches, 

and the fact that certain species are ideal for physiological and behavioral investigations 

under controlled conditions. These studies have been summarized in some 

excellent books, including those by Guthrie and Tindall (1968), Cornwell (1968), Huber 

et al. (1990), Bell and Adiyodi (1982a), and Rust et al. (1995). The last two were devoted 

to single species, the American and the German cockroaches, respectively. As a result of 

this emphasis on Blattaria amenable to culture, cockroaches are often discussed as 

though they are a homogeneous grouping, typified by species such as Periplaneta americana 

and Blattella germanica. In reality the taxon is amazingly diverse. Cockroaches can 

resemble, among other things, beetles, wasps, flies, pillbugs, and limpets. Some are hairy, 

several snorkel, some chirp, many are devoted parents, and males of several species, surprisingly, 

light up. 

The publication most responsible for alerting the scientific community to the diversity 

exhibited by the 99% of cockroaches that have never set foot in a kitchen is The Biotic 

Associations of Cockroaches, by Louis M. Roth and Edwin R. Willis, published in 1960. 

Its encyclopedic treatment of cockroach ecology and natural history was an extraordinary 

achievement and is still, hands down, the best primary reference on the group in 

print. Now, nearly 50 years later, we feel that the subject matter is ripe for revisitation. 

The present volume was conceived as a grandchild of the Roth and Willis book, and relies 

heavily on the information contained in its progenitor. Our update, however, narrows 

the focus, includes recent studies, and when possible and appropriate, frames the 

information within an ecological and evolutionary context. 

This book is intended primarily as a guided tour of non-domestic cockroach species, 

and we hope that it is an eye-opening experience for students and researchers in behavioral 

ecology and evolution. Even we were surprised at some recent findings, such as the

estimate by Basset (2001) that cockroaches constitute approximately 

24% of the arthropod biomass in tropical 

tree canopies worldwide, and hints from various studies 

suggesting that cockroaches may ecologically replace termites 

in some habitats (Chapter 10). We address previously 

unexplored aspects of their biology, such as the relationship 

with microbes that lies at the heart of their 

image as anathema to civilized households (Chapter 5). 

As our writing progressed, some chapters followed unpredicted 

paths, particularly evident in the one on mating 

strategies (Chapter 6). We became fascinated with 

drawings of male and female genitalia that are buried in 

the taxonomic literature and that suggest ongoing, internally 

waged battles to determine paternity of offspring. It 

is the accessibility of this kind of information that can 

have the most impact on students searching for a dissertation 

topic, and we cover it in detail at the expense of addressing 

more familiar aspects of cockroach mating biology. 

We planned the book so that each chapter can be 

mined for new ideas, new perspectives, and new directions 

for future work. 

An interesting development since Roth and Willis 

(1960) was published is that the definition of a cockroach 

Fig. P.1 A phylogeny of cockroaches based on cladistic analysis of 175 morphological and life 

history characters; after Klass and Meier (2006), courtesy of Klaus Klass. Assignation of genera 

to subfamilies is after Roth (2003c) and differs somewhat from that of K & M, who place Archiblatta 

in the Blattinae and Phoetalia in the Epilamprinae. Pseudophyllodromiinae used here is 

Plecopterinae in K & M. Based on their results, K & M suggest that Lamproblattinae and Tryonicinae 

be elevated to family-level status. Mukha et al. (2002, Fig. 2) summarize additional hypotheses 

of higher-level relationships. Phylogenetic trees of Vrs˘anský et al. (2002, Fig. 364) and 

Grimaldi and Engel (2005, Fig. 7.60) include fossil groups. Lo et al. (2000), Klass (2001, 2003), 

and Roth (2003c) discuss major issues. 

is somewhat less straightforward than it used to be. Cockroaches 

are popularly considered one of the oldest terrestrial 

arthropod groups, because insects with a body plan 

closely resembling that of extant Blattaria dominated the 

fossil record of the Carboniferous, “The Age of Cockroaches.” 

The lineage that produced extant cockroaches, 

however, radiated sometime during the early to mid- 

Mesozoic (e.g., Labandeira, 1994; Vršanský, 1997; Grimaldi 

and Engel, 2005). Although the Carboniferous fossils 

probably include the group that gave rise to modern 

Blattaria, they also include basal forms of other taxa. 

Technically, then, they cannot be considered cockroaches, 

and the Paleozoic group has been dubbed “roachoids” 

(Grimaldi and Engel, 2005), among other things. Recent 

studies of extant species are also blurring our interpretation 

of what may be considered a cockroach. Best evidence 

currently supports the view that termites are nested 

within the cockroaches as a subgroup closely related to 

the cockroach genus Cryptocercus. We devote Chapter 9 

to developing the argument that termites evolved as eusocial, 

juvenilized cockroaches. 

Roth (2003c) recognized six families that place most 

cockroach species: Polyphagidae, Cryptocercidae, Noctixii 

PREFACE

colidae, Blattidae, Blattellidae, and Blaberidae; the majority 

of cockroaches fall into the latter three families. His 

paper was used as the basis for assigning the cockroach 

genera discussed in this book to superfamily, family, and 

subfamily, summarized in the Appendix. Despite recent 

morphological and molecular analyses, the relationships 

among cockroach lineages are still very much debated at 

many levels; Roth (2003c) summarizes current arguments. 

For general orientation, we offer a recent, strongly 

supported hypothesis by Klass and Meier (2006) (see fig. 

P.1). In it, there is a basal dichotomy between the family 

Blattidae and the remaining cockroaches, with the rest 

falling into two clades. The first consists of Cryptocercidae 

and the termites as sister groups, with these closely related 

to the Polyphagidae and to Lamproblatta. The other 

clade consists of the Blattellidae and Blaberidae, with the 

Anaplectinae as most basal and Blattellidae strongly paraphyletic 

with respect to Blaberidae. One consequence 

of the phylogenetic uncertainties that exist at so many 

taxonomic levels of the Blattaria is that mapping character 

states onto phylogenetic trees is in most cases premature. 

An analysis of the evolution of some wing characters 

in Panesthiinae (Blaberidae) based on the work of Maekawa 

et al. (2003) is offered in Chapter 2, a comparative 

phylogeny of cockroaches and their fat body endosymbionts 

(Lo et al., 2003a) is included in Chapter 5, and key 

symbiotic relationships are mapped onto a phylogenetic 

tree of major Dictyopteran groups in Chapter 9. 

Since the inception of this book nearly 15 years ago, the 

world of entomology has lost two of its giants, William J. 

Bell and Louis M. Roth. It was an enormous responsibility 

to finish the work they initiated, and I missed their 

wise counsel in bringing it to completion. If just a fraction 

of their extraordinary knowledge of and affection for 

cockroaches shines through in the pages that follow, I will 

consider the book a success. This volume contains unpublished 

data, observations, and personal communications 

of both men, information that otherwise would 

have been lost to the scientific community at large. Bill 

Bell’s observations of aquatic cockroaches are in Chapter 

2, and his unpublished research on the diets of tropical 

species is summarized in Chapter 4. Lou Roth was the acknowledged 

world expert on all things cockroach, and 

was the “go to” man for anyone who needed a specimen 

identified or with a good cockroach story to share. The 

content of his conversations and personal observations 

color the text throughout the book. Bill’s and Lou’s notes 

and papers were kindly loaned to me by their colleagues 

at the University of Kansas and Harvard University, respectively. 

I found it revealing that on Lou’s copy of a paper 

by Asahina (1960) entitled “Japanese cockroaches as 

household pest,” the s in the last word was rather emphatically 

scratched out. 

A large number of colleagues were exceedingly generous 

in offering their time and resources to this project, 

and without their help this volume never would have seen 

the light of day. For advice, information, encouragement, 

references, photographs, illustrations, permission to use 

material, or for supplying reprints or other written matter 

I am glad to thank Gary Alpert, Dave Alexander, David 

Alsop, L.N. Anisyutkin, Jimena Aracena, Kathie Atkinson, 

Calder Bell, David Bignell, Christian Bordereau, Michel 

Boulard, Michael Breed, John Breznak, Remy Brossut, 

Valerie Brown, Kevin Carpenter, Randy Cohen, Stefan 

Cover, J.A. Danoff-Burg, Mark Deyrup, R.M. Dobson, 

C. Durden, Betty Faber, Robert Full, César Gemeno, Fabian 

Haas, Johannes Hackstein, Bernard Hartman, Scott 

Hawkes, W.F. Humphreys, T. Itioka, Ursula Jander, Devon 

Jindrich, Susan Jones, Patrick Keeling, Larry Kipp, Phil 

Koehler, D. Kovach, Conrad Labandeira, Daniel Lebrun, 

S. Le Maitre, Tadao Matsumoto, Betty McMahan, John 

Moser, I. Nagamitsu, M.J. O’Donnell, George Poinar, Colette 

Rivault, Edna Roth, Douglas Rugg, Luciano Sacchi, 

Coby Schal, Doug Tallamy, Mike Turtellot, L. Vidlička, 

Robin Wootton, T. Yumoto, and Oliver Zompro. 

I am particularly indebted to Horst Bohn, Donald 

Cochran, Jo Darlington, Thomas Eisner, Klaus Klass, 

Donald and June Mullins, Piotr Naskrecki, David Rentz, 

Harley Rose, and Ed Ross for their generosity in supplying 

multiple illustrations, and to George Byers, Jo Darlington, 

Lew Deitz, Jim Hunt, Klaus Klass, Nathan Lo, 

Kiyoto Maekawa, Donald Mullins, Patrick Rand, David 

Rentz, and Barbara Stay for reviewing sections or chapters 

of the book and for spirited and productive discussions. 

Anne Roth and the Interlibrary Loan and Document 

Delivery Services at NCSU were instrumental in 

obtaining obscure references. I thank Vince Burke and the 

Johns Hopkins University Press for their patience during 

the overlong gestation period of this book. I am sure that 

there are a great number of people whose kindness and 

contributions eased the workload on Bill Bell and Lou 

Roth during the early stages of this endeavor, and I thank 

you, whoever you are. 

Christine A. Nalepa 

PREFACE 

xiii


Cockroaches


ONE 

Shape, Color, and Size 

many a cockroach 

believes himself as beautiful 

as a butterfly 

have a heart o have 

a heart and 

let them dream on 

—archy, “archygrams” 

The image that floats to consciousness at mention of the word cockroach is one based on 

experience. For most people, it is the insect encountered in the sink during a midnight 

foray into the kitchen, or the one that is pinned splay legged on a wax tray in entomology 

class. While these domestic pests and lab “rats” do possess a certain subtle beauty, 

they are rather pedestrian in appearance when compared to the exuberance of design and 

color that characterizes insects such as beetles and butterflies. Nonetheless, these dozen 

or so familiar cockroaches constitute a half percent or less of described species and can 

be rather poor ambassadors for the group as a whole. Our goal in this chapter, and indeed, 

the book, is not only to point out some rather extraordinary features of the cockroaches 

with which we are already acquainted but to expand the narrow image of the 

group. Here we address their outward appearance, the externally visible morphological 

features, and how their environment helps shape them. 

GENERAL APPEARANCE AND ONTOGENY 

The standard cockroach body is flattened and broadly oval, with a large, shield-like 

pronotum covering the head, ventrally deployed, chewing mouthparts, and long, highly 

segmented antennae. The forewings (tegmina) are typically leathery and the hindwings 

more delicate and hyaline. The coxae are flattened and modified to house the femur, so 

that when the legs are tucked in close to the body the combined thickness of the two segments 

is reduced. A comprehensive discussion of the morphological features of cockroaches, 

particularly those of importance in recognizing and describing species, is given 

in Roth (2003c). 

Like other hemimetabolous insects, cockroach nymphs generally resemble adults except 

for the absence of tegmina and wings; these structures are, however, sometimes indicated 

by non-articulated, lobe-like extensions of the meso- and metanotum in later developmental 

stages. Early instars of both sexes have styles on the subgenital plate; these 

1

are usually lost in older female instars and are absent in 

adult females. Juveniles have undeveloped and poorly 

sclerotized genitalia and they often lack other characters 

useful in species identification. Nymphs of Australian 

soil-burrowing cockroaches, for example, are difficult to 

tell apart because the pronotal and tergal features that 

distinguish the various species are not fully developed 

(Walker et al., 1994). In some taxa, nymphal coloration 

and markings differ markedly from those of adults, making 

them scarcely recognizable as the same species (e.g., 

Australian Polyzosteria spp.—Tepper, 1893; Mackerras, 

1965a). In general, the first few instars of a given species 

can be distinguished from each other on the basis of nonoverlapping 

measurements of sclerotized morphological 

features such as head width or leg segments. In older 

stages, however, accumulated variation results in overlap 

of these measurements, making it difficult to determine 

the stage of a given nymph. This variation results from intermolt 

periods that differ greatly from individual to individual, 

not only in different stages, but also within a 

stage (Scharrer, 1946; Bodenstein, 1953; Takagi, 1978; 

Zervos, 1987). The difficulty in distinguishing different 

developmental stages within a species and the nymphs of 

different species from each other often makes young developmental 

stages intractable to study in the field. Consequently, 

the natural history of cockroach juveniles is 

virtually unknown. 

Dimorphism 

In addition to dimorphism in the presence of wings 

(Chapter 2) and overall body size (discussed below), male 

and female cockroaches may differ in the color and shape 

of the body or in the size, color, and shape of specific body 

parts. The general shape of the male, particularly the abdomen, 

is often more attenuated than that of the female. 

Several sex-specific morphological differences suggest 

that the demands of finding and winning a mate are 

highly influential in cockroach morphological evolution. 

Dimorphism is most pronounced in species where males 

are active, aerial insects, but the females have reduced 

wings or are apterous. These males may have large, 

bulging, nearly contiguous eyes while those of the more 

sedentary female are flattened and farther apart, for example, 

several species of Laxta and Neolaxta (Mackerras, 

1968b; Roth, 1987a, 1992) and Colapteroblatta compsa 

(Roth, 1998a). Male morphology in the blattellid genera 

Escala and Robshelfordia is completely different from that 

of the opposite sex (Roth, 1991b). Such strong sexual dimorphism 

makes associating the sexes difficult, particularly 

when related species are sympatric (Roth, 1992); as 

a result, conspecific males and females are sometimes 

described as separate species. Additional sexual dimorphisms 

include the presence of tergal glands on males of 

many species, and the size and shape of the pronotum. 

Asymmetry 

Cockroaches tend to have an unusually high level of fluctuating 

asymmetry (Hanitsch, 1923), defined as small, 

random differences in bilateral characters. The cockroach 

tarsus is normally composed of five segments, but on one 

leg it may have just four. Spines on the femora also may 

vary in number between the right and left sides of the 

same individual. In both characters a reduction more often 

occurs on the left side of the body. Wing veins may be 

simple on one side and bifurcated on the other. This tendency 

often makes it difficult to interpret the fossil record, 

where so much of our information is based on wings. 

Asymmetries of this type are widely used as a measure of 

fitness because they result from developmental instability, 

the ability of an organism to withstand developmental 

perturbation. Of late, fluctuating asymmetry has become 

a major but controversial topic in evolutionary 

biology (e.g., Markow, 1995; Nosil, 2001), but is unstudied 

in the Blattaria. Less subtle bilateral asymmetries also 

occur in cockroaches; gynandromorphs are reported in 

Periplaneta americana, Byrsotria fumigata (Willis and 

Roth, 1959), Blattella germanica (Ross and Cochran, 

1967), and Gromphadorhina portentosa (Graves et al., 

1986). 

Pronotum 

The large, shield-shaped pronotum is a defining characteristic 

of cockroaches and its size, shape, curvature, and 

protuberances have systematic value in certain groups 

(e.g., Perisphaeriinae, Panesthiinae). Some cockroaches 

are more strongly hooded than others, that is, the head 

ranges from completely covered by the pronotum to almost 

entirely exposed. In some species the pronotum is 

flat, in others it has varying degrees of declivity. At its extreme 

it may form a cowl, shaped like an upside down U 

in section. The border of the pronotum may be recurved 

to varying degrees, forming a gutter around the sides, 

which sometimes continues into the cephalic margin. 

The majority of species of Colapteroblatta, for example, 

have the lateral wings of the pronotum deflexed and the 

edges may be ridged or swollen (Hebard, 1920 [1919]; 

Roth, 1998a, Fig. 1-6). In a few cases the pronotum can 

resemble the headpiece of certain orders of nuns (Fig. 

1.1A). Some species of Cyrtotria have pronota perforated 

with large, semilunar pores in both sexes; these may be 

the openings of glands (Fig. 1.1B) (Shelford, 1908). The 

shape of the pronotum can vary within a species, with 

distinct forms correlated with varying degrees of wing re- 

2 COCKROACHES

Fig. 1.1 Variations in pronotal morphology. (A) Female of 

Cyrtotria marshalli, three-quarter view. (B) Female of Cyrtotria 

pallicornis, three-quarter view; note large lateral pores. (C) 

Male of Princisia vanwaerebeki, lateral view. (D) Female of 

Pilema mombasae, dorsal view. (E) ditto, lateral view. After 

Shelford (1908) and Van Herrewege (1973). Not drawn to scale. 

Fig. 1.2 Male Microdina forceps (Panesthiinae) from India. 

Photo by L.M. Roth. 

duction (e.g., African Ectobius—Rehn, 1931). Both males 

and females of Microdina forceps have the anterior pronotal 

margins extended into a pair of curved spines, resembling 

the forceps of earwigs or the mandibles of staghorn 

beetles (Fig. 1.2) (Roth, 1979b). In females these are about 

2 mm long, and in males they are slightly longer (2.5 

mm). In Bantua valida the lateral margins of the pronotum 

in both sexes are curved upward, but only in the female 

are the caudad corners prolonged into “horns” (Kumar, 

1975). 

Functionally, the pronotum is a versatile tool that can 

serve as a shield, shovel, plug, wedge, crowbar, and battering 

ram. Those cockroaches described as “strongly 

hooded,” with the head concealed under the extended anterior 

edge of the pronotum, are often burrowers. The 

large, flat pronotum of Blaberus craniifer, for example, 

serves as a wedge and protects the head when used in the 

oscillating digging motion described by Simpson et al. 

(1986). In museum specimens of Pilema spp. the channel 

between the pronotal disc and lateral bands is often 

chocked with dirt, leading Shelford (1908) to conclude 

that the pronotum (Fig. 1.1D,E) is used in digging the 

neat round holes in which these cockroaches are found. 

Adult Cryptocercus have been observed using the pronotum 

as a tool in two different contexts. When they are 

cleaning and maintaining their galleries, the insects use 

the pronotum as a shovel to move frass and feces from 

place to place and to tamp these materials against gallery 

walls (CAN, unpubl. obs.). During aggressive encounters 

the pronotum is used to block access to galleries and to 

push and butt intruders (Seelinger and Seelinger, 1983; 

Park and Choe, 2003b). In male Nauphoeta cinerea, combatants 

try to flip rivals onto their backs by engaging the 

edge of their pronotum under that of their opponents 

(Ewing, 1967). In species with strong sexual differences 

in pronotal morphology, dimorphism is likely related 

to sexual competition among males. In Elliptorhina, 

Princisia, and Gromphadorhina, males have heavy, welldeveloped 

knobs on their pronota and use them to battle 

rivals (Fig. 1.1C) (Van Herrewege, 1973; Beccaloni, 1989). 

When males charge, their knobbed pronotal shields come 

together with an audible sound (Barth, 1968c). In Geoscapheini 

(Blaberidae), males often have conspicuous 

pronotal tubercles that are absent in the female, and have 

the anterior edge thickened and prominently upturned 

(Walker et al., 1994); Macropanesthia rhinoceros is named 

for the blunt, horn-like processes projecting from the surface 

of the pronotum in males (Froggatt, 1906). Individuals 

of M. rhinoceros are most often observed above 

ground when they have “fallen on to their backs and are 

unable to right themselves” (Day, 1950). It is unknown if 

these are all males, and the result of nocturnal battles. The 

allometry of male combat weaponry has not been examined 

in cockroaches. 

In some cockroach species the pronotum is used to 

both send and receive messages and thus serves as a tool 

in communication. In N. cinerea there are about 40 parallel 

striae on the ventral surface of the latero-posterior 

edges of the pronotum. The insects stridulate by rubbing 

these against the costal veins of the tegmina (Roth and 

Hartman, 1967). The pronotum is also very sensitive to 

SHAPE, COLOR, AND SIZE 3

tactile stimulation in this species. Patrolling dominant 

males of N. cinerea tap members of their social group on 

the pronotum with their antennae, evoking a submissive 

posture in lower-ranking members (Ewing, 1972). Similarly, 

reflex immobilization in Blab. craniifer can result 

from antennal tapping of the pronotal shield by another 

individual (Gautier, 1967). 

COLOR 

As in many other insect groups, the suborder Blattaria encompasses 

species with both cryptic and conspicuous 

coloration. The former decreases the risk of detection, 

and the latter is often used in combination with chemical 

defenses and specific behaviors that discourage predators. 

Color patterns can vary considerably within a species, 

contributing to taxonomic difficulties (Mackerras, 

1967a), and in a few cockroaches color variation is correlated 

with geographic features, seasonal factors, or both. 

Two subspecies of Ischnoptera rufa collected at high elevations 

in Costa Rica and Mexico are darker than their 

counterparts collected near sea level (Hebard, 1916b). 

Adults of Ectobius panzeri in Great Britain are darker at 

higher latitudes, and females have a tendency to darken 

toward the end of the breeding season (Brown, 1952). 

Parcoblatta divisa individuals are typically dark in color, 

but a strikingly pale morph is found in Alachua County, 

Florida. No dark individuals were found in a series of 

several hundred specimens taken from this location, and 

the pale form has not been collected elsewhere (Hebard, 

1943). Color variation among developmental stages within 

a species may be associated with changing requirements 

for crypsis, mimicry, or aposematicism. Adults of Panchlora 

nivea, for example, are pale green, while the juvenile 

stages are brown (Roth and Willis, 1958b). 

Many cockroaches are dark, dull-colored insects, a 

guise well suited to both their cryptic, nocturnal habits 

and their association with decaying plant debris. Several 

species associated with bark have cuticular colors and 

patterns that harmonize with the backgrounds on which 

they rest. Trichoblatta sericea lives on Acacia trees, blending 

nicely with the bark of their host plant (Reuben, 

1988). Capucina rufa lives on and under the mottled bark 

of fallen trees and seems to seek compatibly patterned 

substrates on which to rest (WJB, pers. obs.). A cloak of 

background substrate enhances crypsis in some species. 

Female Laxta spp. may be encrusted with soil or a parchment-like 

membrane (Roth, 1992), and Monastria biguttata 

nymphs are often covered with dust (Pellens and 

Grandcolas, 2003). 

Not unexpectedly (Cott, 1940), there are dramatic differences 

in coloration between the cockroaches on the 

dayshift versus the nightshift. Day-active cockroaches 

tend to fall into three broad categories: first, the small, active, 

colorful, canopy cockroaches; second, the chemically 

defended, aposematically colored species; and third, 

those that are Batesian mimics of other taxa. Patterned, 

brightly colored insects active in the canopy in brilliant 

sunshine have a double advantage against predators. They 

are not only cryptic against colorful backgrounds, but 

they are obscured by rapidly changing contrast when 

moving in and out of sun flecks (Endler, 1978). A number 

of aerial cockroach species have translucent wing covers, 

tinted green or tan, that provide camouflage when 

they are sitting exposed on leaves (Perry, 1986). 

Among the best examples of aposematic coloration are 

in the Australian Polyzosteriinae (Blattidae). Nocturnal 

species in the group are usually striped yellow and brown, 

but the majority are large, wingless, slow-moving, diurnal 

cockroaches fond of sunning themselves on stumps 

and shrubs. They are very attractive insects, often metallically 

colored, or spotted and barred with bright orange, 

red, or yellow markings (Rentz, 1996; Roach and Rentz, 

1998). When disturbed, they may first display a warning 

signal before resorting to defensive measures. Platyzosteria 

castanea and Pl. ruficeps adults assume a characteristic 

stance with the head near the ground and the abdomen 

flexed upward at a sharp angle, revealing orange-yellow 

markings on the coxae and venter. Continued harassment 

results in the discharge of an evil-smelling liquid “so execrable 

and pungent that it drove us from the spot” 

(Shelford, 1912a). Elegant day-flying cockroaches in the 

genera Ellipsidion and Balta (Blattellidae) can be observed 

basking in the sun and exhibit bright orange colors 

suggestive of Müellerian mimicry rings (Rentz, 1996). 

Cockroaches in the genus Eucorydia (Polyphaginae) are 

usually metallic blue insects, often with orange or yellow 

markings on the wings (Asahina, 1971); little is known of 

their habits. The beautiful wing patterns of some fossil 

cockroaches are suggestive of warning coloration. Some 

Spiloblattinidae, for example, had opaque, black, glossy 

wings with red hyaline windows (Durden, 1972; Schneider 

and Werneburg, 1994). 

Several tropical cockroaches mimic Coleoptera in size, 

color, and behavior. This is evident in their specific 

names, which include lycoides, buprestoides, coccinelloides, 

dytiscoides, and silphoides. Shelford (1912a) attributes 

beetle-mimicry in the Blattaria to the similar body types 

of the two taxa. Both have large pronota and membranous 

wings covered by thickened elytra or tegmina.“Only 

a slight modification of the cockroach form is required to 

produce a distinctly coleopterous appearance.” Vršanský 

(2003) described beautifully preserved fossils of small, 

beetle-like cockroaches that were day active in Mesozoic 

forests (140 mya). Extant species of Prosoplecta (Pseudophyllodromiinae) 

(Fig. 1.3) have markedly convex oval or 

4 COCKROACHES

Fig. 1.3 Species of Prosoplecta that mimic beetles. (A) Pr. 

bipunctata; (B) Female Pr. trifaria, which resembles the light 

morph of the leaf beetle Oides biplagiata; (C) Pr. nigra; (D) Pr. 

gutticolis; (E) Pr. nigroplagiata; (F) Pr. semperi, which resembles 

the coccinellid Leis dunlopi; (G) Pr. quadriplagiata; (H) Pr. mimas; 

(I) Pr. coelophoroides, which resembles the coccinellid 

Coelophora formosa. After Shelford (1912a). Information on 

coleopteran models is from Wickler (1968). 

circular bodies, smooth and shiny tegmina that do not exceed 

the tip of the abdomen, and short legs and antennae; 

they are colored in brilliant shades of orange, red, and 

black. These cockroaches are considered generalized mimics 

of coccinellids and chrysomelids, as in most cases their 

models are unknown. Wickler (1968), however, indicates 

that females of Pr. trifaria (Fig.1.3B) resemble the light 

morph of the leaf beetle Oides biplagiata, while males of 

this cockroach species resemble the dark morph of the 

same beetle. Both models and mimics can be collected 

at the same sites and at the same time of year in the 

Philippines. Members of the blattellid subfamily Anaplextinae 

in Australia are diurnal and resemble members 

of the chrysomelid genus Monolepta with which they occur 

(Rentz, 1996). Schultesia lampyridiformis resembles 

fireflies (Lampyridae) so closely that they cannot be distinguished 

without close examination (Belt, 1874); on his 

first encounter with them LMR took them into a darkened 

hold of the research vessel Alpha Helix to see if they 

would flash (they did not). Other cockroach species have 

the black and yellow coloration associated with stinging 

Hymenoptera, and Cardacopsis shelfordi (Nocticolidae) 

runs and sits like an ant, with the body held high off the 

ground (Karny, as cited by Roth, 1988). All these mimics 

are thought to be palatable. There is at least one suggested 

instance of a cockroach serving as a model: Conner and 

Conner (1992) indicate that a South American arctiid 

moth (Cratoplastis sp.) mimics chemically protected Blattaria. 

Cockroaches may be devoid of pigmentation in three 

general situations. The most common includes new 

hatchlings and freshly molted individuals of any species 

(Fig. 1.4), often reported to extension agents as albinos. 

These typically gain or regain their normal coloration 

within a few hours. The second are the dependent young 

nymphs of cockroach species that display extensive 

parental care. The first few instars of Cryptocercus, Salganea, 

and some other subsocial cockroaches are altricial, 

with pale, fragile cuticles (Nalepa and Bell, 1997). In 

Cryptocercus pigmentation is acquired gradually over the 

course of their extended developmental period. Lastly, 

cockroaches adapted to the deep cave environment lack 

pigment as part of a correlated character loss typical of 

many taxa adapted to subterranean life. Color has no signal 

value for guiding behavior in aphotic environments; 

neither is there a need for melanin, which confers protection 

from ultraviolet radiation. Desiccation resistance afforded 

by a thick cuticle is superfluous in the consistently 

high humidity of deep caves, and mechanical strength is 

not demanded of insects that live on the cave walls and 

floor (Kalmus, 1941; Culver, 1982; Kayser, 1985). 

Adults of burrowing cockroaches, on the other hand, 

typically possess dark, thick cuticles that are abrasion 

resistant, are able to withstand mechanical stress, and 

provide insertions of considerable rigidity for the attachment 

of muscles, particularly leg muscles (Kalmus, 1941; 

Day, 1950). This thick-skinned group includes the desertburrowing 

Arenivaga, as well as the soil- and woodburrowing 

Panesthiinae and Cryptocercidae. Adults of 

Fig. 1.4 Freshly ecdysed Blaberus sp. in stump, Ecuador. Photo 

courtesy of Edward S. Ross. 


Fig. 1.5 One of the largest and one of the smallest known cockroaches. Left, adult female of Megaloblatta 

blaberoides from Costa Rica; the ootheca is that of Megaloblatta regina from Ecuador. 

Right, female nymph of Attaphila fungicola; ventral view of specimen cleared and mounted on a 

slide, courtesy of John Moser. Photos by L.M. Roth and E.R. Willis. 

these taxa are long lived, requiring a sturdy body to 

weather the wear and tear of an extended adult life (Kalmus, 

1941; Karlsson and Wickman, 1989). They also can 

be large-bodied insects, with allometric scaling of cuticle 

production resulting in disproportionately heavy integuments 

(Cloudsley-Thompson, 1988). The pronotum of 

M. rhinoceros is 100 thick, and the cuticle of the sternites 

is 80 , almost twice that of the tergites. The considerable 

bulk of the abdomen normally rests on the ground, 

thus requiring greater abrasion resistance (Day, 1950). 

BODY SIZE 

The general public has always been fascinated with “giant” 

cockroaches. Discoveries of large species, whether 

alive or in the fossil record, are thus guaranteed a certain 

amount of attention. The concept of body size, however, 

is qualitative and multivariate in nature (McKinney, 

1990). Consider two cockroaches that weigh the same but 

differ in linear dimensions. Is a lanky, slender species bigger 

than one with a stocky morphotype? Neotropical 

Megaloblatta blaberoides (Nyctiborinae) triumphs for 

overall length (head to tip of folded wing) (Fig. 1.5). The 

body measures 66 mm, and when the tegmina are included 

in the measurement, its length tops out at 100 

mm. This species has a wingspan of 185 mm (Gurney, 

1959), about the length of a new pencil. Also in contention 

among the attenuated, lighter-bodied cockroaches 

are several in the oft-cultured genus Blaberus. Blaberus 

giganteus may measure 80 mm overall (60 mm body 

length) and female Blab. craniifer 62 mm. Pregnant females 

of the latter weigh about 5 g (Nutting, 1953a). A 

male Archimandrita tessalata measured by Gurney (1959) 

stretched to 85 mm, and one of the largest species in West 

Africa (more than 60 mm) is Rhyparobia ( Leucophaea) 

grandis (Kumar, 1975). Recently, a large cockroach in the 

genus Miroblatta was discovered in caves and rock shelters 

in limestone formations in East Kalimantan, the Indonesian 

section of Borneo. 1 The cockroach was widely 

reported as being 100 mm in length (e.g., BBCNews, 23 

December 2004). Two males measured by Drs. Anne Bedos 

and Louis Deharveng were 60 mm, but they noted 

that some specimens, particularly females, may be larger. 

The cockroach is a streamlined, long-legged species that 

moves very slowly on tiptoe, with the body elevated up 

over the substrate. It is a beautiful reddish-brown, with 

lighter-colored legs and wings that are about half the 

length of the abdomen. 

In the heavyweight division, the undisputed champs 

are the wingless, burrowing types. The Australian soilburrowing 

behemoth M. rhinoceros weighs in at 30 g or 

more, and can measure 85 mm in length. Macropanesthia 

rothi is sized similarly to M. rhinoceros, but is more robust 

in the thorax and legs (Rugg and Rose, 1991; Walker et al., 

1. For information on the species, we thank Patricia Crane, 

Leonardo Salas, Scott Stanley, and Louisa Tuhatu of the Nature 

Conservancy, and Louis Deharveng, Anne Bedos, Yayuk Suhardjono, 

and Cahyo Rachmadi, the entomologists in the expedition 

that discovered the species. The cockroach was identified by P. 

Grandcolas. 

6 COCKROACHES

1994). Males of Macropanesthia are frequently mistaken 

for small tortoises during periods of surface activity 

(Rentz, 1996). The Malagasian G. portentosa can reach 78 

mm in length (Gurney, 1959), and G. grandidieri, with a 

body length of 85 mm, rivals M. rhinoceros in size (Walker 

et al., 1994). 

The oft-repeated myth that the Carboniferous was the 

“Age of Giant Cockroaches” is based on the size of fossil 

and modern cockroaches that were known during the late 

1800s. More recently described species of extant cockroaches 

raise the modern mean, and scores of recently 

collected small fossil species will no doubt lower the Paleozoic 

mean (Durden, 1988). The fossil record also may 

be biased in that large organisms have better preservation 

potential, are easier to find, and can better survive incarceration 

in fine- and coarse-grained sediments (Carpenter, 

1947; Benton and Storrs, 1996). Small cockroaches, 

on the other hand, may be filtered from the fossil record 

because they are more likely to be swallowed whole by fish 

during transport in flowing water (Vishniakova, 1968). 

The largest fossil cockroach to date is an undescribed 

species from Columbiana County, Ohio, which has a 

tegmen length of at least 80 mm (Hansen, 1984 in Durden, 

1988); a complete fossil from the same location has 

recently received media attention (e.g., Gordner, 2001). 

Nonetheless, the tenet that no fossil cockroach exceeds in 

size the largest living species (Scudder, 1886; F.M. Carpenter 

in Gurney, 1959) still applies. It would not be unreasonable 

to suggest that we are currently in the age of 

giant cockroaches (C. Durden, pers. comm. to CAN)! 

At the other end of the scale, the smallest recorded 

cockroaches are mosquito sized species collected from the 

nests of social insects, where a minute body helps allow 

for integration into colony life. The myrmecophile Attaphila 

fungicola is a mere 2.7 mm long (Cornwell, 1968) 

(Fig. 1.5), and Att. flava from Central America is not 

much larger—2.8 mm (Gurney, 1937). Others include 

Myrmecoblatta wheeleri from Florida at less than 3 mm 

(Deyrup and Fisk, 1984), and Pseudoanaplectinia yumotoi 

(4 mm) from Sarawak (Roth, 1995c). Australian 

species of Nocticola measure as little as 3 mm and have 

been collected from both termite nests and caves (Rentz, 

1996). Another category of cockroaches that can be quite 

small are those that mimic Coleoptera. Plecoptera poeyi, 

for example, lives on foliage of holly (Ilex) in Florida and 

is 5–6 mm long (Helfer, 1953). To put the sizes of these 

cockroaches into perspective, it is worthwhile to note that 

the fecal pellets of M. rhinoceros are 10 mm in length 

(Day, 1950). 

As a group, blattellids are generally small in size, but 

several genera are known to include moderately large 

members (Rentz, 1996). A number of tiny aerial Blattellidae 

live in the canopy of tropical rainforests, where 

“their size is suited to hiding in the crease of a leaf or by 

a small bit of moss” (Perry, 1986). Small bodies may confer 

a survival advantage in graduate student lounges; Park 

(1990) noted that American cockroaches live for about 5 

sec when placed in a microwave oven set on “high,” but 

the more diminutive German cockroach lasts for twice 

that long. Small cockroaches usually mature more rapidly 

and have shorter lives than the larger species (Mackerras, 

1970). 

Intraspecific variation in cockroach body size can be 

considerable, with the difference between the largest and 

the smallest specimens so great that they appear to be different 

species (Roth, 1990b). Male length in Laxta granulosa, 

for example, ranges from 14.8 to 25.4 mm (Roth, 

1992). In most cockroaches, the abdominal segments can 

telescope. Extension of the abdomen in live specimens 

and shrinkage in the dead ones, then, may contribute to 

noted variation when body length is the measurement of 

choice. Body size may vary within (e.g., Platyzosteria 

melanaria—Mackerras, 1967b), and between (e.g., Parcoblattini—Roth, 

1990b), geographic locations, or be 

rather consistent over an extensive range (e.g., Ectobius 

larus, E. involutus—Rehn, 1931). No latitudinal clines in 

body size have been reported in cockroaches. 

As in most invertebrates (Fairbairn, 1997; Teder and 

Tammaru, 2005), sexual dimorphism in body size of 

adult cockroaches is common. All patterns are exhibited, 

but a female size bias seems to predominate (Fig. 1.6). Examples 

include Colapteroblatta surinama, where females 

are 18.5–19.0 mm and males are 13.0–15.5 mm in length 

(Roth, 1998a), and the cave-adapted species Trogloblattella 

nullarborensis, with females measuring 34.5–38.5 

mm and males 24–27.5 mm (Roth, 1980). Because of intraspecific 

variation and the multivariate nature of size, 

however, generalizations can be difficult to make. Males 

may measure longer than females, especially when wings 

are included in the measurement, but females are usually 

broader and bulkier, particularly in the abdomen. Both P. 

americana and Supella longipalpa fall into this category 

(Cornwell, 1968) (Fig. 1.7). Several burrowing cockroaches 

exhibit little, if any size dimorphism. There is no 

significant difference in the fresh weight or head capsule 

width of males and females of field-collected pairs of 

Cryptocercus punctulatus, but the dry weight of females is 

slightly higher (Nalepa and Mullins, 1992). In most 

Geoscapheini, males and females are of similar size (Fig. 

1.8) (e.g., Walker et al., 1994), as are several species of Salganea, 

such as Sal. amboinica and Sal. rugulata (Roth, 

1979b). In some Salganea, however, the male is distinctly 

smaller than the female. These include Sal. rectangularis 

(Roth, 1999a) and Sal. morio, where males average 41.9 

mm in length and females 46.6 mm (Roth, 1979b). 

Species in which males outsize females include several 


Fig. 1.6 Diagrammatic representation of cockroach species showing comparative size, comparison 

between males (left) and females (right), degree of size variation within a sex (minimum 

measurement on left, maximum measurement on right), and relationship between tegmen and 

body length. From Cornwell (1968), based on data from Hebard (1917). With permission of Rentokil 

Initial plc. 

Parcoblatta species (Fig 1.6) (Parc. lata, Parc. bolliana, 

Parc. divisa, Parc. pennsylvanica). Males of the latter are 

22–30 mm in length, while females measure 13–20 mm. 

In Parc. fulvescens, however, females outsize the males 

(Cornwell, 1968; Horn and Hanula, 2002). 

Like other animals, the pattern of sexual size dimorphism 

within a cockroach species is related to the relative 

influence of body size on fecundity in females and mating 

success in males. In G. portentosa, males tend to be 

larger than females, and big males are the more frequent 

victors in male-male contests (Barth, 1968c; Clark and 

Moore, 1995). In species where males offer food items to 

the female as part of courtship and mating, nuptial gifts 

may reduce the value of large size in females and increase 

its value in males (Leimar et al., 1994; Fedorka and 

Mousseau, 2002). This hypothesis is unexplored in the 

cockroach species that employ such a mating strategy. 

One proximate cause of female-biased sexual size dimorphism 

in cockroaches is protandry. Males may mature 

faster than females because it gives them a mating advantage, 

but become smaller adults as a consequence. Males 

of Diploptera punctata, for example, usually undergo one 

fewer molt than do females, and require a shorter period 

of time to mature (Willis et al., 1958). Males of Anisogamia 

tamerlana mature in five instars, and females in six 

(Kaplin, 1995). 

Physiological correlates of body size have been examined 

in some cockroaches; these include studies of metabolic 

rate and the ability to withstand extremes of temperature, 

desiccation, and starvation. Coelho and Moore 

8 COCKROACHES

Fig. 1.7 Male (left) and female Supella longipalpa, showing dissimilarity in form between the 

sexes. The female is stouter, and the head is broader with a larger interocular space; the pronotum 

is also larger than that of the male. The tegmina of the female reach only to the end of the abdomen 

and are more chitinous than those of the male (Hebard, 1917). From Back (1937), with 

permission from the Entomological Society of Washington. 

(1989) found that resting metabolic rate for 11 species 

scales allometrically (VO 2 

0.261 M 0.776 ) with mass. As 

in other animals, then, it is metabolically more expensive 

for a small cockroach to maintain a gram of tissue than it 

is for a large one. Relative brain size has been compared 

Fig. 1.8 Harley A. Rose, The University of Sydney, displaying 

male-female pairs of Australian soil-burrowing cockroaches 

(Geoscapheini). Photo by C.A. Nalepa. 

in two cockroach species. The brain (supra-esophageal 

ganglia) of B. germanica occupies about 10 times as much 

of the cranial cavity as does that of M. rhinoceros, a species 

that weighs 320 times more (Day, 1950) (Fig 1.9). There 

is, however, no marked difference in the size of individual 

nerve cell bodies. Day thought that the large size of 

Macropanesthia could be attributed to its burrowing 

habit, which “greatly reduces the effectiveness of gravity 

in limiting size.” More likely factors include the ability to 

withstand predation, the power required to dig in indurate 

soils, and the lower rate of water loss associated 

with a small surface to volume ratio. The latter was suggested 

as being influential in G. portentosa’s ability to 

thrive in the long tropical dry season of Madagascar (Yoder 

and Grojean, 1997); in the laboratory adult females 

survived 0% humidity without food and free water for a 

month. 

The social environment experienced during development 

influences adult body size in cockroaches. Isolated 

cockroach nymphs mature into larger adults than nymphs 

that have been reared in groups, but a smaller adult body 

size occurs when nymphs are reared under crowded conditions 

(e.g., Willis et al., 1958; Woodhead and Paulson, 

1983). Unlike laboratory studies, however, overpopulation 

in nature may be relatively rare, except perhaps in 

some cave populations. Crowded adults are likely to disperse 

or migrate when competition for food and space 

becomes fierce. In all known cases where biotic or abiotic 

factors affect cockroach adult size, these factors act by 

influencing the duration of juvenile growth. In D. punc- 


Fig. 1.9 Comparison of the relative size of the head and anterior 

nervous system in (A) Macropanesthia, and (B) Blattella. 

From Day (1950), with permission from CSIRO Publishing. 

tata, the greater adult weight of isolated animals results 

from a longer nymphal development. Males normally 

have three or four instars, but isolation results in a higher 

proportion of the four-instar type (Woodhead and Paulson, 

1983). A longer postembryonic development induced 

by suboptimal diet resulted in heavier adults in 

Blaptica dubia (Hintze-Podufal and Nierling, 1986). In 

three families of Cryptocercus clevelandi monitored under 

field conditions, some of each litter matured to adults a 

year before their siblings did. Those that matured in 6 yr 

had larger head widths than those that matured in 5 

(Nalepa et al., 1997). 

The dorsoventrally compressed morphotype typical of 

the “classic” cockroach has been taken to extremes in several 

distantly related taxa. These extraordinarily flattened 

insects resemble limpets and live in deep, narrow clefts 

such as those found under loose bark, at the log-soil interface, 

under stones, or in the cracks of boulders and 

rocks. In most species, the borders of the tergites are 

extended, flattened, and held flush with the substrate so 

that a close seal is formed (Fig. 1.10). The proximal parts 

of the femora may be distinctively flattened as part of 

the overall pancake syndrome (Mackerras, 1967b; Roth, 

1992). Included in this group are female West Indian 

Homalopteryx laminata (Epilamprinae) (Kevan, 1962) 

and several Australian taxa. A number of Leptozosteria 

and Platyzosteria spp. (Polyzosteriinae) live in deep, narrow 

clefts under rocks or bark (Mackerras, 1967b; Roach 

and Rentz, 1998). Members of the genus Laxta (Epilamprinae) 

live under eucalypt bark and are common under 

large slabs at the bases of trees (Roth, 1992; Rentz, 1996). 

Some Central and South American Zetoborinae (e.g., 

Lanxoblatta emarginata, Capucina patula) and Blaberinae 

(e.g., Mon. biguttata nymphs) have a comparable 

body type and habitat (Roth, 1992; Grandcolas and Deleporte, 

1994; Pellens and Grandcolas, 2003; WJB, unpubl. 

obs.). Highly compressed morphotypes are associated 

THE ECOLOGY OF MORPHOTYPE 

The smooth, flattened body typical of many cockroaches 

is functionally related to their crevice-inhabiting lifestyle; 

it allows them to slip into narrow, horizontally extended 

spaces like those found in strata of matted, decayed leaves. 

There are, however, a number of variations on the basic 

body type that are exhibited by groups of often distantly 

related cockroaches occupying more or less the same 

ecological niche. These possess a complex of similar morphological 

characters reflecting the demands of their environment. 

Here we briefly profile seven distinct morphological 

groups. Two are defensive morphotypes, and 

two are forms specialized for penetrating solid substrates. 

Desert dwellers, those living in social insect nests, and 

cave cockroaches round out the gallery. 

The Pancake Syndrome 

Fig. 1.10 (A) Ventral view of head and expanded pronotum 

and metanotum of an unidentified, dorsoventrally flattened 

cockroach collected under bark in Brazil; most likely a female 

or nymph of Capucina patula or Phortioeca phoraspoides 

(LMR, pers. obs.). Note debris attached to the pronotal edges, 

which were closely applied to the wood surface. Photo courtesy 

of Edward S. Ross. (B) Female of Laxta friedmani (named after 

LMR’s urologist). Photo courtesy of David Rentz. 

10 COCKROACHES

Fig. 1.11 Mechanisms of cockroach defense against ants. (A) Chemical defense by Diploptera 

punctata. Pogonomyrmex badius is attacking the cockroach on the left, whose defensive glands 

have been removed. The intact cockroach on the right was also attacked by the ants, but it discharged 

a spray of quinones and repelled the attackers. The spray pattern is shown by indicator 

paper on which the cockroach is standing. From Eisner (1958). (B) Defense by conglobulation. 

Adult female of Perisphaerus semilunatus from Thailand, protected from attack by rolling up into 

a ball. From Roth (1981b). (C) Defense by adhesion. A flattened Capucina patula nymph protected 

from attack by hugging the substrate. The body of the cockroach is clearly seen through 

the lateral extensions of the tergites. All photographs courtesy of Thomas Eisner. 

with defense against both abiotic and biotic hazards. In 

the intensely arid climate of Australia, these cockroaches 

squeeze into deep, narrow clefts and cracks to avoid desiccation 

(Mackerras, 1967b). In the Neotropical species, 

it has been demonstrated that compressed bodies confer 

protection against ant attacks (Fig. 1.11C). The insects 

become immobile and cling so tightly to the substrate 

that their vulnerable undersurfaces cannot be harmed 

(Grandcolas and Deleporte, 1994; Pellens and Grandcolas, 

2003; Roth, 2003a). 

The Conglobulators 

Another variation of defensive morphotype is exhibited 

by the wingless half-ellipsoids, those cockroaches that 

are rounded on top and flat on the bottom, like a watermelon 

cut on its long axis. Species of this shape in several 

genera of Perisphaeriinae (Perisphaeria, Perisphaerus, 

and Pseudoglomeris) are able to roll themselves into a ball, 

that is, conglobulate, when alarmed (Fig. 1.12) (Shelford, 

1912a; Roth, 1981b). They are usually rather small, black 

species with a tough cuticle. When enrolled, the posterior 

abdomen fits tightly against the edge of the pronotum.All 

sense organs are covered; there are no gaps for an enemy 

to enter nor external projections for them to grab (Fig. 

1.11B). In some species, the female encloses young 

nymphs that are attached to her venter when she rolls 

up (Chapter 8). Not only are small predators like ants 

thwarted, but the rounded form is very resistant to 

pressure and requires considerable force to crush (Lawrence, 

1953). In other taxa exhibiting this behavior (e.g., 

isopods, myriapods), the rolled posture is maintained 

during long periods of quiescence, so that the animal is 

protected from desiccation as well as enemies (Lawrence, 


Fig. 1.12 Perisphaerus semilunatus female: dorsal, ventral, lateral, and nearly conglobulated. Photos 

by L.M. Roth. 

1953); it is unknown whether that is the case in these 

cockroaches. 

The Burrowers 

Cockroaches that burrow in wood or soil exhibit a remarkable 

convergence in overall body plan related to the 

ability to loosen, transport, and travel through the substrate, 

and to maneuver in confined spaces. These insects 

are often wingless, with a hard, rigid, pitted exoskeleton 

and a thick, scoop-shaped pronotum. The body is stocky 

and compact, and the legs are powerful and festooned 

with stout, articulated spines that provide anchorage 

within the tunnels and leverage during excavation (Fig. 

1.13). The cerci are short, and can be withdrawn into the 

body in Cryptocercus (thus the name) and Macropanesthia. 

Long cerci make backward movement in enclosed 

spaces inconvenient (Lawrence, 1953). 

The similarity in the external morphology of Cryptocercus 

and wood-feeding Panesthiinae is so striking that 

they were initially placed in the same family (Wheeler, 

1904; Roth, 1977). McKittrick (1964, 1965), however, examined 

their genitalia and internal anatomy and demonstrated 

that the resemblance was superficial. Her studies 

resulted in placing the two taxa into distantly related families 

(Cryptocercidae and Blaberidae). They currently offer 

an opportunity to scientists interested in sorting the 

relative influences of phylogeny and ecology in structuring 

life history and behavior. 

The Borers 

Although little to nothing is known of their biology, several 

small cockroaches have a heavy pronotum and exhibit 

the elongated, cylindrical body form typical of many 

wood-boring beetles (Cymorek, 1968). Their appearance 

suggests that these cockroaches drill into solid wood or 

Fig. 1.13 Adult Cryptocercus punctulatus. Photo courtesy of 

Piotr Naskrecki. 

soil because the shape minimizes cross-sectional area, reducing 

the tunnel bore and the force required to advance 

a given body weight. This morphotype is exhibited by 

the genus Colapteroblatta (Epilamprinae) (Roth, 1998a), 

as well as some species of Perisphaeriinae in the genera 

Compsagis, Cyrtotria, Bantua, and Pilema (Shelford, 

1908; Roth, 1973c). Compsagis lesnei typifies this type of 

cockroach (Fig. 1.14) and is a small (9.5 mm in length) 

African species found inside of tree branches (Chopard, 

1952). 

Desert Dwellers 

Cockroaches that live in the desert typically have morphological 

adaptations allowing for the conservation 

of water and for ease in negotiating their sandy environment. 

Adult females and nymphs are shaped like 

smooth, truncated ovals, with short, spined legs (e.g., 

Arenivaga investigata—Friauf and Edney, 1969). The head 

is strongly hooded by the pronotum, and cuticular extensions 

of the thoracic and abdominal tergites cover the 

12 COCKROACHES

Fig. 1.14 Female of the wood-boring cockroach Compsagis 

lesnei. Left, whole body. Right, head and pronotum: ventral 

view (top), lateral view (bottom). From Chopard (1952), with 

permission of Société Entomologique de France. 

Fig. 1.15 Male of the desert-dwelling Iranian cockroach Leiopteroblatta 

monodi, exhibiting the long hairs that create an insulating 

boundary layer of air in many desert-dwelling cockroaches. 

From Chopard (1969), with permission of the Société 

Entomologique de France. 

body and the legs. The periphery of the body is fringed by 

hairs that directly contact the substrate when the insect is 

on the desert surface, creating a boundary layer of air and 

trapping respiratory water (Fig. 1.15). A microclimate 

that is more favorable than the general desert atmosphere 

is thus maintained under the body (Vannier and Ghabbour, 

1983). Most of these desert dwellers are in the 

Polyphagidae, but some Polyzosteria spp. (Blattidae) that 

inhabit dry areas of Australia are apterous, are broadly 

Fig. 1.16 Cockroaches that live in nests of social insects. (A) 

Male myrmecophile Myrmecoblatta wheeleri; left, ventral view; 

right, dorsal view. From Deyrup and Fisk (1984), with permission 

of M.A. Deyrup. (B) Female myrmecophile Attaphila 

fungicola. From Wheeler (1900). (C) Termitophile Nocticola 

termitophila; left, female; right, male. From Silvestri (1946). 

Not drawn to scale. 

oval, and have a “remarkably hairy covering” (Mackerras, 

1965a). 

Myrmecophiles/Termitophiles 

Myrmecophiles are just a few millimeters long, oval in 

shape, strongly convex, and rather uniformly covered 

with short, fine setae (Fig. 1.16A,B). They are typically 

apterous or brachypterous, the legs and antennae are 

short, and in some species the eyes are reduced. Att. 

fungicola (Blattellidae) have no more than 70 ommatidia 

per eye (Wheeler, 1900; Roth, 1995c). No glands are obvious 

that may function in appeasing their hosts. Myrme- 


coblatta wheeleri (Polyphagidae) run rapidly, and when 

disturbed withdraw their appendages under the body and 

adhere tightly to the substrate (Deyrup and Fisk, 1984). 

This behavior is similar to the defensive behavior of flattened 

Neotropical species (Fig. 1.11C) and suggests that 

although they appear integrated into colony life, a wariness 

of their predator hosts remains of selective value. 

Wheeler (1900) suggested that Att. fungicola is a “truly 

cavernicolous form, living in caves constructed by its emmet 

hosts.” It is the species of Nocticola taken from termite 

nests, however, that exhibit the delicate, elongate 

body, attenuated appendages, and pale cuticle typical of 

cave-adapted insects (and of most other Nocticolidae— 

Roth, 1988, 1991a; Fig. 1.16C). 

Cave Dwellers 

Cave-adapted cockroaches exhibit a suite of morphological 

characters common to cave-dwelling taxa around the 

world. These include depigmentation and thinning of cuticle, 

the reduction or loss of eyes, the reduction or loss of 

tegmina and wings, the elongation and attenuation of appendages, 

and a more slender body form (Howarth, 1983; 

Gilbert and Deharveng, 2002). A large nymph of the 

genus Nelipophygus collected in Chiapas, Mexico, for example, 

cannot survive outside of its cave and is colorless, 

slender, and 20 mm long; it has extremely long antennae 

and limbs, and has no trace of compound eyes or pigment 

(Fisk, 1977). Males of Alluaudellina cavernicola exhibit a 

remarkable parallel reduction of eyes and wings (Fig. 

1.17) (Chopard, 1932). Eye size ranges from well developed 

to just three ommatidia, with intermediates between. 

Individuals of Nocticola australiensis from the 

Chillagoe region of Australia also show a consistent gradation 

of forms, from less troglomorphic in southern 

caves to more troglomorphic in the north (Stone, 1988). 

The pattern of variation is very regular, unlike the more 

complex variation seen in some other taxa. The Australian 

species Paratemnopteryx howarthi, for example, 

also demonstrates the entire range of morphological variation, 

but both the reduced-eye, brachypterous forms 

and the large-eyed, winged morphs can occur in the same 

cave (Chopard, 1932; Roth, 1990b). 

One consequence of regressive evolution of visual 

structures in cave-adapted animals is that orientation and 

communication have to be mediated by non-visual systems. 

Thus, the loss of the visual modality is often complemented 

by the hypertrophy of other sensory organs 

(Nevo, 1999; Langecker, 2000). In cockroaches, this may 

include the elongation of the legs, antennae, and palps 

(Fig. 1.18). In All. cavernicola the antennae are three times 

the length of the body (Vandel, 1965), and both Noc. australiensis 

and Neotrogloblattella chapmani have very long, 

Fig. 1.17 Variation in eye and wing development in cavedwelling 

Alluaudellina cavernicola. (A,B) Eye development in 

macropterous males; (C) eye development in a micropterous 

males; (D,E,F) eye development in wingless females. After 

Chopard (1938). 

slender legs and elongated maxillary palps. Palps are long 

in Ischnoptera peckorum as well (Roth, 1980, 1988). In 

nymphs of some species of Spelaeoblatta from Thailand 

it is only the front pair of legs that is elongated, which together 

with their narrow, elongated pronotum confers a 

mantid-like appearance (Vidlička et al., 2003). Long legs 

are adaptive in reaching across gaps, negotiating irregular 

substrates, and covering larger areas per unit of expended 

energy (Howarth, 1983). Elongated antennae and palps 

function in extending the sensory organs, allowing the insects 

to detect food and mates faster and at a greater distance 

from their bodies. Consequently, less energy is required 

for resource finding (Hüppop, 2000), a decided 

advantage in a habitat where food may be scarce and population 

densities low. Cave-dwelling Paratemnopteryx exhibit 

subtle shifts in the number and type of antennal and 

mouthpart sensilla as compared to surface-dwelling relatives 

(Bland et al., 1998a, 1998b). There is a moderate reduction 

in the mechano–contact receptors and an increase 

in the number of olfactory sensilla in the cave 

dwellers when compared to similar sized epigean species. 

The elongation of appendages is typically correlated with 

a behavioral change. Troglomorphic cockroaches move 

with slow deliberation while probing with their long appendages. 

They “thereby avoid entering voids from which 

no escape is possible” (Howarth, 1983). Weinstein and 

Slaney (1995) found that highly troglomorphic species of 

14 COCKROACHES

Fig. 1.18 Male of the Western Australian troglobitic cockroach 

Nocticola flabella from a cave in the Cape Range, Western Australia 

(Roth, 1991c). Top, dorsal view; bottom, grooming its 

metathoracic leg.; photo courtesy of the Western Australia Museum, 

via W.F. Humphreys. 

Paratemnopteryx were able to avoid baited pitfall traps, 

but the slightly troglomorphic species readily entered 

them. Overall, cockroaches may experience less selection 

pressure for improved non-visual sensory organs than 

many other insects; cave colonizers that are already nocturnal 

may require little sensory improvement (Langecker, 

2000). 

Selection Pressures 

Food limitation is most commonly suggested as the selective 

basis of the syndrome of characters associated with 

cave-dwelling organisms. First, many of the characters are 

directed toward improved food detection (e.g., elongation 

of appendages) and food utilization (e.g., lower 

metabolic and growth rate, starvation resistance, slow 

movement, fewer eggs) (Poulson and White, 1969; Hüppop, 

2000; Gilbert and Deharveng, 2002). Second, troglomorphic 

species are more often found in caves that lack 

sources of vertebrate guano (Vandel, 1965; Culver, 1982). 

It is the combination of scarce food and the consistently 

dark, humid environment of deep caves, however, that 

best accounts for the reductions and losses that characterize 

troglomorphism. Eyes are complex organs, expensive 

to develop and maintain. Animals rarely have sophisticated 

visual systems unless there is substantial selection 

pressure to favor them (Prokopy, 1983). Optical 

sensors are useless in the inky blackness of deep caves and 

“compete” with non-visual systems for available metabolites 

and energy (Culver, 1982; Nevo, 1999). Photoreception 

is also related to a complex of behavioral and 

morphological traits that become functionless in the permanent 

darkness of a cave. These include visually guided 

flight and signaling behavior based on cuticular pigmentation 

(Langecker, 2000). Cave-dwelling cockroaches in 

north Queensland, Australia, display a remarkable degree 

of correlation between levels of troglomorphy and the 

cave zone in which they occur. In the genera Nocticola and 

Paratemnopteryx, the most modified species described by 

LMR are found only in the stagnant air zones of deep 

caves, while the slightly troglomorphic species of Paratemnopteryx 

are concentrated in twilight transition zones 

(Howarth, 1988; Stone, 1988). Because cockroaches live 

in a variety of stable, dark, humid, organic, living spaces, 

however, reductive evolutionary trends are not restricted 

to cavernicolous species (discussed in Chapter 3). Nocticola 

( Paraloboptera) rohini from Sri Lanka, for example, 

lives under stones and fallen tree trunks. The female 

is apterous; the males have small, lateral tegminal lobes 

but lack wings, and the eyes are represented by just a few 

ommatidia (Fernando, 1957). 

Many cave cockroaches diverge from the standard 

character suite associated with cave-adapted insects. They 

may exhibit no obvious troglomorphies, or display some 

characters, but not others. Blattella cavernicola is a habitual 

cave dweller but shows no structural modifications 

for a cave habitat (Roth, 1985). Neither does the premise 

that some cave organisms diverge from the morphological 

profile because they live in energy-rich environments 

such as guano piles (Culver et al., 1995) always hold true 

for cockroaches. Paratemnopteryx kookabinnensis and 

Para. weinsteini are associated with bats (Slaney, 2001), 

yet both show eye and wing reduction. Heterogeneity in 

these characters may occur for a variety of reasons. The 

surface-dwelling ancestor may have exhibited varying 

levels of morphological reduction or loss prior to becoming 

established in the cave (i.e., some losses are plesiomorphic 

traits) (Humphreys, 2000a). Such is likely the 

case for the two species of Paratemnopteryx mentioned 

above; most species in the genus have reduced eyes, lack 

pulvilli, and are apparently “pre-adapted” for cave dwelling 

(Roth, 1990b). Species also may be at different stages 

of adaptation to the underground environment (Peck, 

1998). Generally, regression increases and variability 

decreases with phylogenetic age (Culver et al., 1995; 

Langecker, 2000). Nocticola flabella is probably the most 

troglobitic cockroach known (Fig. 1.18); the male is 4–5 


mm long, eyeless, with reduced tegmina and no hindwings, 

has very long legs and antennae, and is colorless 

except for amber mouthparts and tegmina (Roth, 1991c). 

This high level of regressive evolution is also found in 

other species found in deep caves of the Cape Range in 

western Australia and is consistent with the apparent 

great age of this fauna (Humphreys, 2000b). Other 

sources of variation that may play a role include ecological 

differences within and among caves, continued gene 

flow between epigean and cave populations, the accumulation 

of neutral mutations, developmental constraints, 

or some combination of these (Culver, 1982; Slaney and 

Weinstein, 1997b; Hüppop, 2000; Langecker, 2000). 

Retention of Sexually Selected Characters 

In several cave-adapted cockroaches, male tergal glands, 

which serve as close-range enticements to potential 

mates, do not vary in concert with other morphological 

features. The glands can be large, or numerous and complex, 

despite the otherwise troglomorphic features displayed 

by the male. Trogloblattella nullarborensis is found 

deep within limestone caves in Australia, and is much 

larger than other blattellids. It lacks eyes, and has reduced 

wings and elongated appendages and antennae. Its color, 

however, has not been modified. Adults are medium to 

dark brown, and the male has huge tergal glands (Mackerras, 

1967c; Richards, 1971; Rentz, 1996). Similarly, 

males in the genus Spelaeoblatta are pale in color and have 

reduced eyes, brachypterous wings, and long legs and antennae; 

however, they have large, elaborate tergal glands 

on two different tergites, and in Sp. myugei, large tubercles 

of unknown function on tergites 5 through 8 (Fig. 

Fig. 1.19 The cave-adapted cockroach species Spelaeoblatta 

myugei from Thailand. (A) Dorsal view of male. Note large tergal 

glands on tergites 3 and 4, and paired tubercles on tergites 

5–8. (B) Dorsal view of female. (C) Lateral view of male abdomen 

and its tubercles. From Vidlička et al. (2003), with permission 

from Peter Vršanský and the Taylor & Francis Group. 

1.19) (Roth and McGavin, 1994; Vidlička et al., 2003). 

Tergal glands are rare in Nocticola spp., but Noc. uenoi 

uenoi living in the dark zone of caves on the Ryukyu Islands 

has a prominent one (Asahina, 1974). The genitalia 

of male cave cockroaches also can be very complex, despite 

the regressive evolution evident in other body parts, 

for example, Nocticola brooksi (Roth, 1995b) as well as 

other Nocticolidae (Roth, 1988). Mating behavior in 

cave-adapted cockroaches has not been described. 

16 COCKROACHES

TWO 

Locomotion: 

Ground, Water, and Air 

i can walk on six feet 

or i can walk on four feet 

maybe if i tried hard enough 

i could walk on two feet 

but i cannot walk on five feet 

or on three feet 

or any odd number of feet 

it slews me around 

so that i go catercornered 

—archy, “a wail from little archy” 

Cockroaches were once placed in the suborder Cursoria (Blatchley, 1920) (Lat., runner) 

because the familiar ones, the domestic pests, are notorious for their ground speed on 

both horizontal and vertical surfaces. Indeed, the rapid footwork of these species has 

made cockroach racing a popular sport in a number of institutions of higher learning. 

Like most animal taxa, however, cockroaches exhibit a range of locomotor abilities, 

reflecting ease of movement in various habitats. On land, the limits of the range are mirrored 

in body designs that maximize either speed or power: the lightly built, long-legged 

runners, and the bulkier, more muscular burrowers. There is a large middle ground of 

moderately fast, moderately powerful species; however, research has focused primarily 

on the extremes, and it is on these that we center our discussion of ground locomotion. 

We touch on cockroach aquatics, then address the extreme variation in flight capability 

exhibited within the group. Finally, we discuss ecological and evolutionary factors associated 

with wing retention or loss. 

GROUND LOCOMOTION: SPEED 

Periplaneta americana typifies a cockroach built to cover ground quickly and is, relative 

to its mass, one of the fastest invertebrates studied. It has a lightly built, somewhat fragile 

body and elongated, gracile legs capable of lengthy strides. The musculature is typical 

of running insects, but the orientation of the appendages with respect to the body differs. 

The middle and hind pairs point obliquely backward, and the leg articulations are 

placed more ventrally than in most insects (Hughes, 1952; Full and Tu, 1991). Periplaneta 

americana has a smooth, efficient stride, and at most speeds, utilizes an alternating 

tripod gait, that is, three legs are always in contact with the ground. The insect can stop 

at any point in the walking pattern because its center of gravity is always within the support 

area provided by the legs. At a very slow walk the gait grades into a metachronal 

wave, moving from back to front, that is, left 3-2-1, then right 3-2-1 (Hughes, 1952; Del- 

17

Most are long-legged with the ventral surfaces of the tarsi 

spined (Rentz, 1996). 

Stability and Balance 

Fig. 2.1 Ground reaction force pattern for Periplaneta americana 

running bipedally, with the metathoracic legs propelling 

the body. Vertical forces periodically decrease to zero, indicating 

that all six legs are off the ground in an aerial phase. From 

Full and Tu (1991), with the permission of Robert J. Full and 

Company of Biologists Ltd. 

comyn, 1971; Spirito and Mushrush, 1979). At its highest 

speed, P. americana shifts its body weight posteriorly and 

becomes bipedal by sprinting on its hind legs. The body 

is raised well off the ground and an aerial phase is incorporated 

into each step in a manner remarkably similar 

to bipedal lizards (Fig. 2.1). Periplaneta can cover 50 

body lengths/sec in this manner (Full and Tu, 1991). As 

pointed out by Heinrich (2001), by that measure they can 

run four times faster than a cheetah. Other studied cockroaches 

are slower and less efficient. The maximum speed 

for Blaberus discoidalis, for example, is less than half of 

that of P. americana. The former is a more awkward runner, 

with a great deal of wasted motion (Full and Tu, 

1991). Speed is known to vary with temperature (Blab. 

discoidalis), substrate type, sex, and developmental stage 

(B. germanica) (Wille, 1920; Full and Tullis, 1990). 

Hughes and Mill (1974) note that it is the ability to 

change direction very rapidly that often gives the impression 

of great speed. The ability to run swiftly and to fly effectively 

are not mutually exclusive. Imblattella panamae, 

a species that lives among the roots of epiphytic orchids, 

is fast moving both on wing and on foot (Rentz, 1987, 

pers. comm. to CAN). Hebard (1916a) noted that Cariblatta, 

a genus of diminutive insects, “ran about with 

great speed and took wing readily, though usually flying 

but short distances. When in flight, they appeared very 

much like small brownish moths.” As a group, blattellids 

are generally very fast moving, especially when pursued. 

Impressive locomotor performances are not limited to 

flat surfaces; cockroaches can scamper over uneven ground 

and small obstacles with agility and speed. Their vertically 

oriented joint axes act in concert with a sprawled posture 

to allow the legs to perform like damped springs during 

locomotion. As much as 50% of the energy used to displace 

a leg is stored as elastic strain energy, then returned 

(Spirito and Mushrush, 1979; Dudek and Full, 2000; Watson 

et al., 2002). In experiments on rough terrain, running 

P. americana maintained their speed and their alternating 

tripod gait while experiencing pitch, yaw, and roll 

nearly 10-fold greater than on flat surfaces (Full et al., 

1998). Blaberus discoidalis scaled small objects (5.5 mm) 

with little change in running movements. Larger (11 mm) 

objects, however, required some changes in kinematics. 

The insects first assessed the obstacle, then reared up, 

placed their front tarsi on it, elevated their center of mass 

to the top of the object, then leveled off. The thorax was 

capable of substantial ventral flexion during these movements 

(Watson et al., 2002). 

In a remarkable and no doubt entertaining series of experiments, 

Jindrich and Full (2002) studied self-stabilization 

in Blab. discoidalis by outfitting cockroaches with 

miniature cannons glued to the thorax. They then triggered 

a 10 ms lateral blast designed to knock the cockroach 

suddenly off balance in mid-run (Fig. 2.2). The insects 

successfully regained their footing in the course of a 

single step, never breaking stride. Stabilization occurred 

too quickly to be controlled by the nervous system; the 

mechanical properties of the muscles and exoskeleton 

were sufficient to account for the preservation of balance. 

Fig. 2.2 Blaberus discoidalis with an exploding cannon backpack 

attempting to knock it off balance. Photo courtesy of 

Devin Jindrich. 

18 COCKROACHES

There is some concern over gangs of these armed research 

cockroaches escaping and riddling the ankles of unsuspecting 

homeowners with small-bore cannon fire (Barry, 

2002). 

A healthy cockroach flipped onto its back is generally 

successful in regaining its footing. In most instances 

righting involves body torsion toward one side, flailing 

movements of the legs on the same side, and extension of 

the opposite hind leg against the substrate to form a strut. 

The turn may be made to either the right or left, but some 

individuals were markedly biased toward one side. In 

some cases a cockroach will right itself by employing a 

forward somersault, a circus technique particularly favored 

by B. germanica (Guthrie and Tindall, 1968; Full et 

al., 1995). If flipped onto its back on a smooth surface 

Macropanesthia rhinoceros is unable to right itself and will 

die (H. Rose, pers. comm. to CAN). 

Aging cockroaches tend to dodder. There is a decrease 

in spontaneous locomotion, the gait is altered, slipping is 

more common, and there is a tendency for the prothoracic 

leg to “catch” on the metathoracic leg. The elderly 

insects develop a stumbling gait, and have difficulty 

climbing an incline and righting themselves (Ridgel et al., 

2003). 

The recent spate of sophisticated research on mechanisms 

of cockroach balance and control during locomotion 

is in part the result of collaborative efforts between 

robotic engineers and insect biologists to develop blattoid 

walking robots. The ultimate goal of this “army of biologically 

inspired robots” (Taubes, 2000) is to carry sensory 

and communication devices to and from areas that 

are difficult or dangerous for humans to enter, including 

buildings collapsed by earthquakes, bombs, or catastrophic 

weather events. In some cases living cockroaches 

have been outfitted with small sensory and communication 

backpacks (“biobots”), and their movement steered 

via electrodes inserted into the bases of the antennae 

(Moore et al., 1998). Gromphadorhina portentosa was the 

species selected for these experiments because they are 

large, strong enough to carry a reasonable communications 

payload, easy to maintain, and “no one would get 

too upset if we were mean to them” (T. E. Moore, pers. 

comm. to LMR). One limitation is that biobots could be 

employed only in the tropics or during the summer in 

temperate zones. Perhaps engineers should start thinking 

about making warm clothing for them, modeled after 

spacesuits (LMR, pers. obs.). 

Orientation by Touch 

Like many animals active in low-light conditions, cockroaches 

often use tactile cues to avoid obstacles and guide 

their locomotion. The long filiform antennae are positioned 

at an angle of approximately 30 degrees to the 

body’s midline when the insect is walking or running in 

open spaces (P. americana). These serve as elongate 

probes that “cut a sensory swath” approximately 5.5 cm 

wide (Camhi and Johnson, 1999). The antennae are also 

used to maintain position relative to walls and other vertical 

surfaces. One antenna is dragged along the wall, and 

when it loses touch the cockroach veers in the direction 

of last contact. The faster they run the closer their position 

to the wall. Experimentally trimming the antennae 

also results in a path closer to the wall. The insects quickly 

compensate for projections or changes in wall direction, 

but depart from convex walls with diameters of less than 

1 m (Creed and Miller, 1990; Camhi and Johnson, 1999). 

German cockroaches placed in a new environment tend 

to follow edges, but wander more freely in a familiar environment 

(Durier and Rivault, 2003). 

GROUND LOCOMOTION: CLIMBING 

The ability of a cockroach to walk on vertical and inverted 

horizontal surfaces (like ceilings) is predicated on specific 

features of the tarsi. The tarsus is comprised of five subsegments 

or tarsomeres. Each of the first four of these 

may bear on its ventral surface a single, colorless pad-like 

swelling called the euplanta, plantula, or tarsal pulvillus. 

At the apex of the fifth tarsal subsegment is a soft adhesive 

lobe called the arolium, which lies between two large 

articulated claws (Fig. 2.3). The surface of the arolium is 

sculptured and bears a number of different types of sensillae. 

Both arolia and euplantae deform elastically to assure 

maximum contact with a substrate and to conform 

to the microsculpture of its surface. Little cockroach footprints 

left behind on glass surfaces indicate that secretory 

material aids in forming a seal with the substrate. Generally, 

when a cockroach walks on a smooth or rough surface, 

some of the euplantae touch the substrate, but the 

arolia do not. The tarsal claws function only when the insect 

climbs rough surfaces, sometimes assisted by spines 

at the tip of the tibiae. The arolium is employed primarily 

when a cockroach climbs smooth vertical surfaces 

such as glass; the claws spread laterally and the aroliar pad 

presses down against the substrate (Roth and Willis, 

1952b; Arnold, 1974; Brousse-Gaury, 1981; Beutel and 

Gorb, 2001). These structures can be quite effective; an 

individual of Blattella asahinai that landed on a car windshield 

was not dislodged until the vehicle reached a speed 

of 45 mph ( 72 kph) (Koehler and Patternson, 1987). 

Cockroach species vary in the way they selectively employ 

their tarsal adhesive structures. Diploptera punctata, 

for example, stands and walks with the distal tarsomeres 

raised high above the others, and lowers them only when 

climbing, but in Blaberus the distal tarsomeres are always 

LOCOMOTION: GROUND, WATER, AND AIR 19

Fig. 2.3 Adhesive structures on the legs of cockroaches. Top, 

euplantae (arrows) on tarsal segments of two cockroach 

species. (A) Hind tarsus of male Opisthoplatia orientalis; (B) 

hind tarsus of male Comptolampra liturata. From Anisyutkin 

(1999), with permission of L.N. Anisyutkin. Bottom, apical and 

dorsal view of the pretarsi of the prothoracic legs in two cockroach 

species, showing the claws and arolia. Left, a cockroach 

able to walk up a vertical glass surface (male Periplaneta americana); 

right, one unable to do so (female Blatta orientalis). a 

arolium; b aroliar pad; c tarsal claw. After Roth and Willis 

(1952b). 

in contact with the substrate (Arnold, 1974). Within a 

species, there may be ontogenetic differences. Unlike 

adults, first instars of B. germanica are 50% faster on glass 

than they are on rough surfaces, probably because they 

use euplantae more than claws or spines during locomotion 

(Wille, 1920).Variation in employing adhesive structures 

is related to the need to balance substrate attachment 

with the need to avoid adhesion and consequent 

inability to move quickly on various surfaces. Both Blatta 

orientalis and Periplaneta australasiae walk readily on 

horizontal glass surfaces if they walk “on tiptoe” with the 

body held high off the substrate. If the euplantae of the 

mid and hind legs are allowed to touch the surface, they 

become attached so firmly that the cockroach can wrench 

itself free only by leaving the tarsi behind, clinging to the 

glass (Roth and Willis, 1952b). 

Tarsal Morphology: Relation to Environment 

Cockroaches vary in their ability to climb (i.e., escape) 

glass containers (Willis et al., 1958). This is due principally 

to the development of the arolium, which varies in 

size, form, and sculpturing and may be absent in some 

species (Arnold, 1974). Blatta orientalis, for example, has 

subobsolete, nonfunctional arolia and is incapable of 

climbing glass (Fig. 2.3). Euplantae may also differ in size 

and shape on the different tarsomeres, be absent from one 

or more, or be completely lacking. The presence or absence 

of these adhesive structures can be used as diagnostic 

characters in some genera (e.g., the genus Allacta 

has euplantae only on the fourth tarsomere of all legs), 

but are of minor taxonomic significance in others (e.g., 

the genera Tivia, Tryonicus, Neostylopyga, Paratemnopteryx) 

(Roth, 1988, 1990b, 1991d). Intraspecifically, variation 

may occur among populations, between the sexes, 

and among developmental stages (Roth and Willis, 

1952b; Mackerras, 1968a). In Paratemnopteryx ( Shawella) 

couloniana and Neotemnopteryx ( Gislenia) australica 

euplantae are acquired at the last ecdysis (Roth, 

1990b). 

Although arolia and euplantae are considered adaptive 

characters related to functional requirements for climbing 

in different environments (Arnold, 1974), it is not 

currently obvious what habitat-related features influence 

their loss or retention in cockroaches. Adhesive structures 

are frequently reduced or lost in cave cockroaches, perhaps 

because clinging mud or the surface tension of water 

on moist walls reduces their effectiveness (Mackerras, 

1967c; Roth, 1988, 1990b, 1991a). It would be instructive 

to determine if the variation in adhesive structures exhibited 

by different cave populations of species like 

Paratemnopteryx stonei can be correlated with variation 

among surfaces in inhabited caves. Arolia are absent in all 

Panesthiinae (Mackerras, 1970), and the two cockroaches 

listed by Arnold (1974) as having both arolia and euplantae 

absent or “only vaguely evident”—Arenivaga investigata 

and Cryptocercus punctulatus—are both burrowers. 

Nonetheless, the loss of arolia and euplantae is not restricted 

to cave and burrow habitats (Roth, 1988); many 

epigean species lack them. Arnold (1974) found it “surprising” 

that the tarsal features are so varied within cockroach 

families and among species that inhabit similar 

environments. A number of authors, however, have emphasized 

that it is the behavior of the animal within its 

habitat, rather than the habitat itself, that most influences 

locomotor adaptations (Manton, 1977; Evans and Forsythe, 

1984; Evans, 1990). The presence and nature of appendage 

attachment devices is thought to be strongly associated 

with a necessity for negotiating smooth, often 

vertical plant surfaces (Gorb, 2001). Thus in a tropical 

forest, a cockroach that perches or forages on leaves during 

its active period may retain arolia and euplantae, but 

these structures may be reduced or lost in a species that 

never ventures from the leaf litter. Pulvilli and arolia are 

very well developed, for example, in Nyctibora acaciana, a 

species that oviposits on ant-acacias (Deans and Roth, 

20 COCKROACHES

Fig. 2.4 Oxygen consumption while running on a treadmill: a cockroach built for speed (Periplaneta 

americana) versus one built for power (Gromphadorhina portentosa). Oxygen peaks 

rapidly in P. americana, and afterward the insect recovers rapidly. There is a lag time before oxygen 

peaks in G. portentosa, and a slow recovery time while the insect “catches its breath.” Note 

difference in scale of y-axis. Reprinted from Herreid and Full (1984), with permission from Elsevier. 

2003). In cockroaches that possess them, variation in 

sculpturing on the arolia may function in maximizing 

tenacity and agility on specific plant surface morphotypes 

(Bernays, 1991). Many species of tropical cockroach do 

not run when on leaves, but instead stilt-walk (WJB, pers. 

obs.). The slow leg movements produce little vibration in 

the substrate, and may allow them to ease past spiders 

without eliciting an attack, a phenomenon called “vibrocrypticity” 

(Barth et al., 1988). 

GROUND LOCOMOTION: POWER 

At the other end of the spectrum from sleek, fast-running 

cockroaches such as P. americana are the muscular, 

shorter-legged species that burrow into soil or wood. 

Their legs are usually ornamented with sturdy spines, 

particularly at the distal end of the tibiae; these function 

to brace the insect against the sides of the burrow, providing 

a stable platform for the transmission of force. 

Fossorial cockroaches are built for power, not speed. 

When forced to jog on a treadmill, all tested cockroach 

species exhibited a classic aerobic response to running; 

oxygen consumption (VO 2 

) rapidly rose to a steady state 

that persisted for the duration of the workout. When exercise 

was terminated, the recovery time of P. americana 

and Blab. discoidalis rivaled or exceeded the performance 

of the best vertebrate runners (Fig. 2.4). Among the slowest 

to recover was the heavy-bodied G. portentosa, which 

took 15–45 min, depending on the speed of the run (Herreid 

et al., 1981; Herreid and Full, 1984). Some individuals 

of G. portentosa exhibited obvious signs of fatigue. 

They stopped, carried their body closer to the substrate, 

and had a hard time catching their breath: respiratory 

movements were exaggerated and the insects maintained 

their spiracles in a wide-open position. 

Burrowing 

Digging behavior in cockroaches has not been studied, 

but the little, mostly anecdotal information we have indicates 

substantial variation, both in the behavior employed 

and in the body part used as a digging tool. There 

are at least two modes of creating tunnels in a hard substrate 

(soil, wood), both of which are accomplished by 

moving the substrate mechanically from in front of the 

insect and depositing it elsewhere. There are also two 

methods of digging into more friable material (guano, 

leaf litter, sand), achieved by insinuating the body into or 

through preexisting spaces. Cockroaches use refined excavation 

and building techniques in burying oothecae 

(Chapter 9). 

Scratch-Digging (Geoscapheini) 

All members of the uniquely Australian Geoscapheini excavate 

permanent underground living quarters in the 

compact, semi-arid soils of Queensland and New South 

Wales. The unbranched burrows of M. rhinoceros can 

reach a meter beneath the surface (Chapter 10); the tunnel 

widens near the bottom into a compartment that 

functions as a nursery and a storage chamber for the dried 

vegetation that serves as food. The distal protibiae are impressively 

expanded to act as clawed spades, driven by the 


Tooth-Digging (Cryptocercidae) 

Cryptocercus spp. chew irregular tunnels in rotted logs, 

but the tunnels are clearly more than a by-product of 

feeding activities. Numerous small pieces of wood are obvious 

in the frass pushed to the outside of the gallery. 

When entering logs, the cockroaches often take advantage 

of naturally occurring crevices (knotholes, cracks), particularly 

at the log-soil interface. Burrows then generally 

follow the pattern of moisture and rot in individual logs. 

Rotted spring wood between successive annual layers is 

often favored. In well-rotted logs, the cockroaches will in 

part mold their living spaces from damp frass. In fairly 

sound logs, galleries are only slightly larger than the diameter 

of the burrower, and may be interspersed with 

larger chambers (Nalepa, 1984, unpubl. obs.). 

Adult Cryptocercus have been observed manipulating 

feces and loosened substrate within galleries. The material 

is pushed to their rear via a metachronal wave of the 

legs. The insect then turns and uses the broad surface of 

the pronotum to tamp the material into place. The tarsi 

are relatively small, and stout spines on the tibiae serve to 

gain purchase during locomotion. The cockroach is often 

upside down within galleries, and like many insects living 

in confined spaces (Lawrence, 1953), frequently walks 

backward, allowing for a decrease in the number of turning 

movements. The body also has a remarkable degree of 

lateral flexion, which allows the insect to bend nearly 

double when reversing direction in galleries (CAN, unpubl. 

obs). 

Fig. 2.5 Macropanesthia rhinoceros, initiating descent into 

sand; photo courtesy of David Rentz. Inset: Detail of mole-like 

tibial claw used for digging; photo courtesy of Kathie Atkinson. 

large muscles of the bulky body (Fig. 2.5). The hard, stout 

spines flick the soil out behind the cockroach as it digs. 

When the insect is moving through an established burrow, 

the spines fold neatly out of the way against the 

shank of the tibia. The tarsi are small and dainty (Park, 

1990). The large, scoop-like pronotum probably serves 

as a shovel. Tepper (1894) described the behavior of Geoscapheus 

robustus supplied with moist, compressed soil: 

“they employ not only head and forelegs, but also the 

other two pairs, appearing to sink into the soil without 

raising any considerable quantity above the surface, nor 

do they appear to form an unobstructed tunnel, as a part 

of the dislodged soil appears to be pressed against the 

sides, while the remainder fills up the space behind the insect. 

A few seconds suffice them to get out of sight.” Soil 

texture and compaction no doubt determine the energetic 

costs of digging and whether burrows remain open 

or collapse behind the excavator. 

Sand-Swimming (Desert Polyphagidae) 

During their active period, fossorial desert Polyphagidae 

form temporary subsurface trails as they “swim” through 

the superficial layers of the substrate. Their activities generate 

a low rise on the surface as the loosely packed sand 

collapses in their wake. The resultant serpentine ridges 

look like little mole runs (Fig. 2.6) (Hawke and Farley, 

1973). During the heat of day, the cockroaches (Arenivaga) 

may burrow to a depth of 60 cm (Hawke and 

Farley, 1973). The bodies of adult females and nymphs are 

streamlined, with a convex thorax and sharp-edged 

pronotum. Tibial spines on the short, stout legs facilitate 

their pushing ability and serve as the principal digging 

tools. These spines are often flattened or serrated, with 

sharp tips. Anterior spines are sometimes united around 

the apex in a whorl, forming a powerful shovel (Chopard, 

1929; Friauf and Edney, 1969). Eremoblatta subdiaphana, 

for example, has seven spines projecting from the front 

tibiae (Helfer, 1953). Also aiding subterranean move- 

Fig. 2.6 Tracks (2–3 cm wide) of Arenivaga sp. at the base of a 

mesquite shrub near Indigo, California. Females and nymphs 

burrow just beneath the surface at night. From Hawke and Farley 

(1973), courtesy of Scott Hawke. Inset: Ventral view of female 

Arenivaga cerverae carrying an egg case. The orientation 

of the egg case is likely an adaptation for carrying it while the 

female “swims” through the sand. Note well-developed tibial 

spines. Photo by L.M. Roth and E.R. Willis. 

22 COCKROACHES

Head-Raising (Blaberus craniifer) 

In studying the burrowing tendencies of Blab. craniifer, 

Simpson et al. (1986) supplied the cockroaches with a 

mixture of peat moss and topsoil, then filmed them as 

they dug into the substrate. The insects were able to bury 

themselves in just a few seconds using a rapid movement 

of the legs, combined with a stereotyped dorsal-ventral 

flexion of the head and pronotum. The combined headraising, 

leg-pushing behavior seems well suited to digging 

in light, loose substrates (litter, dust, guano), but may also 

facilitate expanding existing crevices, like those in compacted 

leaf litter or under bark. This digging technique 

does not require the profound body modifications exhibited 

by cockroaches specialized for burrowing in hard 

substrates, and is therefore compatible with the ability to 

run rapidly. Indeed, the behavior seems well suited to the 

“standard” cockroach body type displayed by Blab. craniifer: 

an expanded, hard-edged pronotum, inflexed head, 

slick, flattened, rather light body, and moderately strong, 

spined legs. 

SWIMMING 

Fig. 2.7 Sensory organs on cerci of adult male Arenivaga sp. 

(A) Ventral view of insect, with the cerci indicated by arrows. 

(B) Posterior end of the abdomen showing the orthogonal position 

of the cerci and rows of tricholiths. (C) Cross section 

through the left cercus to illustrate that the cerci are rotated laterally 

from the horizontal plane. (D–E) Scanning electron micrographs 

showing details of tricoliths on the cerci. (D) Ventral 

view of left cercus; note two parallel rows of tricholiths. (E) 

View from the distal end of the tricholith (tl) rows showing sensilla 

chaetica (sc) and a trichobothrium (tb). Courtesy of H. 

Bernard Hartman. From Hartman et al. (1987), with permission 

from Springer Verlag. 

ments are large spherical sense organs (tricholiths) on 

the ventral surface of the cerci in Arenivaga and other 

polyphagids (Roth and Slifer, 1973). These act like tiny 

plumb bobs in assisting orientation of the cockroaches 

while they move through their quasifluid environment 

(Walthall and Hartman, 1981; Hartman et al., 1987) (Fig. 

2.7). First instars of Arenivaga have only one tricholith on 

each cercus; new ones are added at each molt. Adult females 

have six pairs and males have seven pairs (Hartman 

et al., 1987). 

It seems logical that cockroaches are not easily drowned, 

as they are members of a taxon whose ancestors were associated 

with swamp habitats and “almost certainly able 

to swim” (North, 1929). As anyone who has tried to flush 

a cockroach down the toilet can verify, these insects have 

positive buoyancy and will bob to the surface of the water 

if forced under. A water-repellent cuticle aids surface 

tension in keeping them afloat (Baudoin, 1955). Periplaneta 

americana is a fine swimmer, and can move in a 

straight line at 10 cm/sec. The body is usually arched, 

with the antennae held clear of the water and moving in 

normal exploratory fashion. If the antennae touch a solid 

substrate, the insect turns toward the source of stimulation 

and swims faster. While swimming, the legs are coordinated 

in the same alternating tripod pattern seen 

while walking on land; this differs from the pattern of 

synchronous leg pairs seen in other terrestrial and aquatic 

insects in water. Articulated spines on the tibia of each leg 

are strongly stimulated by movement through water and 

may provide feedback in regulating swimming behavior. 

All developmental stages can swim, but the youngest instars 

are hampered by surface tension (Lawson, 1965; 

Cocatre-Zilgein and Delcomyn, 1990). 

Most P. americana isolated on an artificial island will 

escape within 10 min, with escape more rapid in experienced 

insects (Lawson, 1965). Two strategies are employed, 

reminiscent of those seen in humans at any swimming 

pool. (1) Gradual immersion (the “wader”): the 

surface of the water is first explored with the forefeet (Fig. 


Fig. 2.8 (A) Periplaneta americana testing the water with 

forelegs before (B) taking the plunge. Courtesy of R.M. Dobson. 

2.8). The middle legs then attempt to reach the bottom 

beneath the water, while clinging to the island with the 

rear legs and with the front of the body afloat. Finally, the 

cockroach releases the hind legs, enters completely, and 

swims away. (2) The “cannonball” strategy: after initial 

exploration, the insect retires slightly from the edge, 

crouches, then jumps in, often while fluttering the wings. 

The legs of amphibious cockroaches do not exhibit any 

morphological adaptations for swimming and are no different 

from those of non-aquatic species (Shelford, 1909; 

Takahashi, 1926). Nymphs of many Epilampra spp. swim 

rapidly below the surface (Crowell, 1946; Wolcott, 1950); 

newborn nymphs as well as adults of Ep. wheeleri ( Ep. 

abdomennigrum) swim easily and remain under water a 

good deal of the time (Séin, 1923). Individuals of Poeciloderrhis 

cribrosa verticalis can swim against a current 

velocity of 0.15 m/sec (Rocha e Silva Albuquerque et al., 

1976). Opisthoplatia maculata, on the other hand, rarely 

swims, but instead walks on submerged rocks along 

stream bottoms (Takahashi, 1926). 

Adult cockroaches with fully developed flight organs have 

two sets of wings that reach or surpass the end of the abdomen, 

completely covering the abdominal terga. The 

hindwings are membranous, but the forewings (tegmina) 

are somewhat sclerotized. In most species the tegmina 

cross each other, with the left tegmen covering a portion 

of the right, and with the covered portion of a different 

texture and color. There are also cases where the forewings 

are transparent and similar in size and texture to 

the hindwings (e.g., Paratemnopteryx suffuscula, Pilema 

cribrosa, Nocticola adebratti, Cardacus ( Cardax) willeyi), 

or hardened and elytra-like (e.g., Diploptera and 

other beetle mimics). 

The entire wing apparatus of cockroaches shows clear 

adaptations for a concealed lifestyle (Brodsky, 1994). 

Dorsoventral flattening has altered the structure of the 

thoracic skeleton and musculature, and when at rest the 

wings are folded flat against the abdomen. One exception 

is Cardacopsis shelfordi, whose wings do not lie on the abdomen 

with the tips crossing distally, but diverge as in 

flies (Karny, 1924 in Roth, 1988). Elaborate mechanisms 

of radial and transverse folding allow the delicate hindwings 

to fit under the more robust tegmina. In repose, the 

anal lobe of the hindwing is always tucked under the anterior 

part of the wing (remigium). Polyphagids accomplish 

this with a single fold line (Fisk and Wolda, 1979), 

but in other cockroaches this area is folded along radial 

lines into a simple fan. There may be apical rolling (e.g., 

Prosoplecta nigrovariegata, Pr. coccinella, Choristima spp.) 

or folding (e.g., Anaplecta) of the remigium. In some 

species (e.g., D. punctata), this crease is in the middle of 

the wing, allowing for a folded wing with only half the 

length and a quarter of the area of the unfolded wing (Fig. 

2.9). These more elaborate strategies of wingfolding are 

common in beetle mimics, as it allows for the protection 

of hindwings that exceed the length of the tegmina 

(Shelford, 1912a; Roth, 1994). Patterns of wingfolding, 

together with other wing characters, can be useful in 

cockroach classification (Rehn, 1951; Haas and Wootton, 

1996; Haas and Kukalova-Peck, 2001). A number of 

generic names originate from wing characters, for example, 

Plecoptera (Gr., plaited wing), Chorisoneura (Gr., 

separate veins), Symploce (Gr., woven together), Ischnoptera 

(Gr., slender wing) (Blatchley, 1920). 

Cockroaches are “hindmotor” flyers. The hindwing is 

WINGS AND FLIGHT 

Fig. 2.9 Wing folding in Diploptera punctata; (A) dorsal view, 

right tegmen and wing expanded, longitudinal and transverse 

folds marked as dotted lines; from Tillyard (1926). (B) Posterodorsal 

view of a wing in the process of folding. Drawing by 

Robin Wootton, courtesy of Robin Wootton and Fabian Haas. 

24 COCKROACHES

Fig. 2.10 Flight in Periplaneta americana; consecutive film 

tracings of a single wingbeat. The forewings reach the top of 

the stroke just as the hindwings pass the top of the stroke and 

begin to pronate (#3). As a result, both pairs pronate nearly simultaneously 

(#4), so that the hindwings, moving faster, are 

ahead of the forewings (#5), approach the bottom of the stroke, 

supinate, and go up (#12–20). From Brodsky (1994), by permission 

of Oxford University Press. 

the main source of propulsion (Brodsky, 1994), and the 

two pairs of wings operate independently and slightly out 

of phase (Fig. 2.10). In basal cockroaches the tegmina 

seem to be an integral part of the flight mechanism, but 

in the more derived species their direct use in flight is less 

common (Rehn, 1951). During flight, aerodynamically 

induced bending of the cerci serves as a feedback in 

regulating wingbeat frequency (Lieberstat and Camhi, 

1988). It is generally believed that the majority of winged 

cockroaches are rather inept fliers and lack the ability to 

sustain long-distance flight (Peck and Roth, 1992). Flight 

ability within the group varies, of course, and even weak 

fliers can be quite maneuverable in the air, with various 

strategies for evading predators. A number of small 

tropical species are known to be strong fliers, capable of 

sustained flights in a straight line or with slight lateral 

curves. They are able to increase altitude but cannot hover 

(Farnsworth, 1972). 

Wing Reduction and Flightlessness 

All taxonomic groups of cockroaches include species with 

variably reduced or absent tegmina and hindwings, exposing 

all or part of the dorsal surface of the abdomen. 

The exceptions are those groups in which the distal portion 

of the hindwing is set off by a transverse fold (e.g., 

Diplopterinae, Ectobiinae, Anaplectinae—Rehn, 1951). 

Wing reduction typically affects the hindwings more than 

the tegmina (Peck and Roth, 1992). Even when they are 

reduced, wings are always flexibly joined to the thorax. 

Adults with reduced wings can be distinguished from 

older nymphs, then, because the wing pads of the latter 

are nonflexible extensions of the posterior margins of the 

wing-bearing thoracic segments (Fisk and Wolda, 1979). 

Although in some cockroach groups apterous species are 

tiny and may be passed over by collectors because they resemble 

nymphs (Mackerras, 1968a), some of the largest 

known cockroaches (Macropanesthia) also lack wings. 

Based on information in Rehn (1932b) and Roth and 

Willis (1960), Roff (1990, Table 8) estimated that more 

than 50% of all cockroaches and 50–60% of temperate 

species lack the ability to fly. Vastly different figures also 

have been published. Roff (1994) indicated that just 4% 

of cockroaches are flightless in both sexes, and 24% are 

sexually dimorphic, with males flying and females flightless 

(data from North America, French Guiana, Africa, 

and Malagasy). There are reasons to be cautious when assessing 

cockroach flight ability. First, only a fraction of the 

more than 4000 known cockroach species are included in 

these estimates; volant canopy species in particular may 

be underestimated. Second, flight capability in cockroaches 

is typically based on published descriptions of 

wing morphology in museum specimens. The possession 

of fully developed wings, however, does not necessarily 

mean that a cockroach can fly (Farnsworth, 1972; Peck 

and Roth, 1992). 

A more accurate measure of cockroach flight capability 

may lie in the color of the thoracic musculature of 

freshly killed insects. Kramer (1956) found that the 

pterothoracic musculature of apterous, brachypterous, 

and flightless or feebly flying macropterous cockroaches 

appears hyaline white, while that of strong fliers is opaque 

and conspicuously pink (Table 2.1). These color differences 

are correlated with distinct metabolic differences, 

as reflected in enzymatic activity and oxygen uptake 

(Kramer, 1956). Consequently, cockroaches with white 

musculature may not be able to release energy rapidly 

enough to sustain wing beating (Farnsworth, 1972). In 

cockroaches with pink musculature, the muscles of the 

mesothorax and metathorax are equally pigmented. One 

exception is the “beetle” cockroach D. punctata ( dytiscoides), 

which derives its common name from the fact 

that the somewhat reduced, hardened tegmina resemble 

elytra and cover a pair of long hindwings (Fig. 2.9). In this 

species the mesothoracic muscles are hyaline white, but 

the metathorax bearing the elongated hindwings con- 


Table 2.1. Wing development and its relationship to 

pigmentation of the thoracic musculature. Based on Kramer 

(1956) and Roth and Willis (1960). 

Color of pterothoracic musculature 

Mesothorax Metathorax 

Cockroach species (wing condition) 1 (wing condition) 

Blaberus craniifer Pink (M) Pink (M) 

Blaberus giganteus Pink (M) Pink (M) 

Blatta orientalis White (R) White (R) 

Blattella germanica White (M) White (M) 

Blattella vaga Pink (M) Pink (M) 

Cryptocercus punctulatus White (A) White (A) 

Diploptera punctata White (R) Pink (M) 

Eurycotis floridana White (R) White (R) 

Nauphoeta cinerea White (R) White (R) 

Neostylopyga rhombifolia White (R) White (R) 

Parcoblatta pennsylvanica 

Male Pink (M) Pink (M) 

Female White (R) White (R) 

Parcoblatta virginica 



Periplaneta fuliginosa 


Female White (M) White (M) 

Periplaneta brunnea 



Periplaneta australasiae 



Pycnoscelus surinamensis 2 Pink (M) Pink (M) 

Rhyparobia maderae Pink (M) Pink (M) 

Supella longipalpa 



1 

M macropterous, R reduced, A absent. 

2 

Female morphs with reduced wings exist. 

tains pigmented muscle (Kramer, 1956). Macropterous 

adults with white musculature include Blattella germanica, 

females of Supella longipalpa ( supellectilium), and 

three species of Periplaneta. Both sexes of B. germanica 

and Blattella vaga have fully developed wings (see Plate 5 

of Roth and Willis, 1960), but B. germanica is incapable 

of sustained flight (Brenner et al., 1988). 2 The rosy flight 

muscles of B. vaga are an indication that it is volant, but 

its flight behavior is unknown. The Asian cockroach Blattella 

asahinai is morphologically very similar (Lawless, 

2. It is, however, a frequent flier on airplanes (Roth and Willis, 

1960). 

1999) and very closely related (Pachamuthu et al., 2000) 

to B. germanica, but flies readily and strongly (Brenner et 

al., 1988); presumably, dissections would indicate that it 

has pigmented flight muscles. Males of Su. longipalpa are 

fleet runners and can take to the air for short distances, 

but females are unable to fly (Hafez and Afifi, 1956). Another 

example of a macropterous but flightless species is 

Thorax porcellana (Epilamprinae). Both sexes are fully 

winged, but only the male uses them for short flights and 

only rarely (Reuben, 1988). 

The correlation between flight muscle pigmentation 

and the physiological ability to sustain flight has been examined 

most extensively in P. americana. In tests on laboratory 

strains tethered females (white flight muscles) 

could sustain no more than a 3–12 sec flight, compared 

to 5–15 min in males (pink flight muscles). Moreover, 

freshly ecdysed male P. americana have white pterothoracic 

muscles and flight behavior similar to that of adult 

females: they flutter weakly or plummet when tossed into 

the air. The flight behavior of these young males changes 

in conjunction with the postmetamorphic development 

of pink pigmentation in their musculature (Kramer, 

1956; Farnsworth, 1972; Stokes et al., 1994). In the tropics 

P. americana is reportedly an excellent flyer, and is 

known in some locales as the “Bombay canary.” It has 

been observed flying out of sewers and into buildings. It 

was also spotted in a German zoo flying distances of up 

to 30 m, in fairly straight lines or in flat arcs about 0.5 to 

1.5 m above the ground (Roth and Willis, 1957). It is unclear, 

however, whether these volant P. americana are 

males only, or if both sexes in natural populations can fly. 

Rehn (1945) indicated that the flying ability of Periplaneta 

(species unspecified) is “often exercised and by both 

sexes.” Female P. americana from laboratory cultures in 

two U.S. locations and one in Germany, however, remained 

earthbound during flight tests (Kramer, 1956). 

Appel and Smith (2002) report that P. fuliginosa females 

with fully formed oothecae are capable of sustained flight 

on warm, humid evenings in the southern United States, 

but laboratory-reared females of this species sank like 

rocks when tossed in the air (Kramer, 1956). Perhaps 

females lose the ability to fly when raised in culture. At 

least one study demonstrated that flight initiation in 

P. americana was significantly affected by the temperature 

at which they were reared (Diekman and Ritzman, 

1987), and flight performance in other insects is known 

to quickly suffer under laboratory selection (Johnson, 

1976). 

A physiological change in flight musculature no doubt 

precedes or accompanies morphological wing reduction, 

but may be the only modification if the tegmina and 

wings have a functional significance other than flight. 

Full-sized wings may be retained in flightless species be- 

26 COCKROACHES

cause they may act as parachutes, controlling the speed 

and direction of jumps and falls. German cockroaches, 

for example, will glide short distances when disturbed 

(Koehler and Patternson, 1987). Tegmina and wings may 

be used as tools in territorial or sexual signaling; males in 

several species flutter their wings during courtship. They 

also may serve as stabilizers during high-speed running, 

as physical protection for the abdomen and associated 

tergal glands, in visual defense from enemies (crypsis, 

mimicry, aposematicism), and, in rare cases, as shelter for 

first instars. 

Ecological Correlates of Flight Condition 

A number of papers have focused on the ecological determinants 

that may select for wing retention versus loss 

in various insect groups. Chopard (1925) was the first to 

examine the phenomenon in cockroaches, and divided 

cockroach genera into one of three wing categories: (1) 

tegmina and hindwings developed in both sexes; (2) 

wings short or absent in females only; and (3) wings short 

or absent in both sexes. He then arranged genera by collection 

locality and concluded that flightlessness was correlated 

with certain geographic locations. Rehn (1932b), 

however, demonstrated that each of the three listed conditions 

can be displayed by different species within the 

same genus, and refuted the idea that flightlessness was 

correlated with geography. Rehn could find no single 

factor that selected for wing reduction in the cockroaches 

he studied (New World continental and West Indian 

species), but thought that “altitude and possibly humidity 

or aridity under special conditions”might be involved. 

More recently, Roff (1990, Table 1) surveyed the literature 

and concluded that cockroaches as well as other insects 

that live in deserts, caves, and social insect nests have a 

higher than average incidence of flightlessness. He also 

found that a lack of flight ability was not exceptionally 

high on islands, in contrast to conventional thought. 

Generalizations on the correlation between flight ability 

and habitat are difficult to make for cockroaches. With 

few exceptions, conclusions are based on wing length, and 

habitat type is inferred from daytime resting sites or 

baited traps. As discussed above, the possession of fullsized 

wings is not always a reliable index of flight ability, 

and the location of diurnal shelter is only a partial indication 

of cockroach habitat use. Although it is safe to assume 

that cockroaches attracted to light traps have some 

degree of flight ability, the traps collect only night-active 

species that are attracted to light, and the ecological associations 

of these remain a mystery. Males of Neolaxta, for 

example, are very rarely seen in the field, but can be collected 

in considerable numbers from light traps (Monteith, 

in Roth, 1987a). Given those caveats (there will be 

more later), we will here examine wing trends in some 

specific habitat categories. 

Islands 

Darwin (1859) first suggested that the isolation imposed 

by living on an island selects for flightless morphologies, 

because sedentary organisms are less likely to perish by 

being gusted out to sea. More recent authors, however, 

have questioned the hypothesis (e.g., Darlington, 1943). 

For one thing, scale is not taken into account. Conditions 

are different for a large insect on a small island versus a 

tiny insect on a substantial one (Dingle, 1996). Roff 

(1990) analyzed the wing condition of insects on oceanic 

islands versus mainland areas (corrected for latitude) and 

found no correlation between island life and a sedentary 

lifestyle. Denno et al.’s (2001a) work on planthoppers in 

the British Virgin Islands also supports this view. 

The observation that a flightless cockroach lives on an 

island does not necessarily mean that the wingless condition 

evolved there. Cockroaches have greater over-water 

dispersal powers than is generally assumed, because they 

raft on or in floating debris and vegetation (Peck, 1990; 

Peck and Roth, 1992). Moreover, cockroaches that live 

under bark or burrow in wood or other dead vegetation 

may be the most likely sailors; this category includes a 

relatively high percentage of wing-reduced species (discussed 

below). Trewick (2000) recently analyzed DNA 

sequences in the blattid Celatoblatta, a flightless genus 

found in New Zealand and in the Chatham Islands, habitats 

separated by about 800 km of Pacific Ocean. The 

island populations were monophyletic, and probably 

dispersed from New Zealand to the islands by rafting 

sometime during the Pliocene (2–6 mya). Members of 

this genus are known to shelter in logs during the day. 

When six small mangrove isles off the coast of Florida 

were experimentally sterilized, Latiblattella rehni and an 

undescribed species in the same genus were early re-invaders 

on several of them (Simberloff and Wilson, 1969). 

Males of Lat. rehni have fully developed, “very delicate” 

(Blatchley, 1920) wings; those of the female are slightly reduced, 

but it is unknown if they are functional. Colonization, 

then, could have been by active or passive flight, 

or by rafting. The Krakatau Islands offered a unique opportunity 

to study the reintroduction of cockroaches into 

a tropical ecosystem from a sterile baseline after a series 

of volcanic eruptions in 1883 stripped them of plant and 

animal life. A 1908 survey found a few cockroach species 

already present, with a subsequent steep colonization 

curve that flattened out after the 1930s (Thornton et al., 

1990). The 17 species reported from the islands by 1990 

include pantropical species (P. americana, Blatta orientalis) 

probably introduced by humans, fully winged 

species (e.g., Balta notulata, Haanina major), those with 


educed wings (Lobopterella dimidiatipes), and species in 

which there is a great deal of variation in wing reduction 

in both sexes (e.g., Hebardina concinna). Neostylopyga 

picea, which has short tegminal pads and lacks wings, also 

is present on the islands and probably arrived by rafting. 

It is generally found in humus and decaying wood (Roth, 

1990a). 

Studies in the Galapagos offer the best evidence that 

the evolution of flightlessness may occur on islands. Eighteen 

species are reported on the Galapagos (Peck and 

Roth, 1992). Of these, the introduced or native (naturally 

occurring tropical American and Galapagos) cockroaches 

are fully winged as adults, except for female Symploce 

pallens. The five endemic species are all partially or 

wholly flightless. Peck and Roth (1992) suggest that three 

natural colonization events took place. First, an early colonization 

by Ischnoptera and loss of flight wings in three 

descendent species, a later colonization by Chorisoneura 

and partial reduction of flight wings in two descendent 

species, and lastly, a recent colonization by Holocampsa 

nitidula and perhaps another Holocampsa sp. These authors 

give a detailed analysis of the process of wing reduction 

in the studied cockroaches, and conclude that 

their data fit the generalization that loss of flight capability 

often accompanies speciation on islands. The authors 

do note, however, that the flightless condition “may not 

be a result of island life per se, but may be a specialization 

for life in more homogenous leaf litter or cave habitats at 

higher elevations on the islands.” 

Mountains 

There are several indications that wing reduction or loss 

in cockroaches may be correlated with altitude. On Mt. 

Kilimanjaro in Africa, for example, fully alate Ectobius 

africanus females were collected only below 1000 m 

(Rehn, 1932b). In Australia, males in the genus Laxta 

may be macropterous, brachypterous, or apterous, but all 

known females lack wings. In the two cases where males 

are not fully winged, both were collected at altitude: Lax. 

aptera (male apterous) from the Brindabella Ranges and 

Snowy Mountains, and Lax. fraucai (male brachypterous) 

from northeastern Australia at 670–880 m (Mackerras, 

1968b; Roach and Rentz, 1998; Roth, 1992). Although 

most Ischnoptera species are fully winged, the flightless 

Ischnoptera rufa debilis occurs at high altitude in Costa 

Rica (Fisk, 1982). The metabolic cost of flight may be substantial 

at the cold temperatures typical of high elevations 

(Wagner and Liebherr, 1992). 

Deserts 

Females of desert cockroach species are generally apterous 

or brachypterous, but males are fully alate (Rehn, 

1932b). The high cost of desiccation during flight may account 

for many cases of wing reduction in desert insects 

(Dingle, 1996), but may be less of a problem for nightactive 

insects like many Blattaria. Rehn (1932b) noted 

that the number of brachypterous and subapterous cockroaches 

in deserts was comparable to that of humid rainforest 

areas of tropical America. It has been suggested that 

the strong tendency for wing reduction among all families 

of Australian cockroaches (Mackerras, 1965a) is a response 

to desert conditions (Chopard, in Rehn, 1932b). 

Almost all of the large Australian group Polyzosteriinae 

are brachypterous or apterous, but not all live in the 

desert. Scabina antipoda, for example, is brachyterous 

and found under bark in the rainforests of eastern Australia 

(Roach and Rentz, 1998). 

Insect Nests 

Cockroaches adapted to living in the nests of social insects 

are always apterous or have wings reduced to varying 

degrees. Pseudoanaplectinia yumotoi, associated with 

Crematogaster sp. ants in canopy epiphytes in Sarawak, is 

among those with the longest wings. The tegmina and 

wings reach to about the sixth tergite in the female, and 

to about the supra-anal plate in the male (Roth, 1995c); 

it is unknown as to whether these allow for flight. Females 

of Nocticola termitofila, from nests of Termes sp. and 

Odontotermes sp. termites, are apterous (Fig. 1.16C). 

Males are brachypterous, with transparent wings about 

half the length of the abdomen (Silvestri, 1946); these are 

fringed around the edges (like thrips) and may allow for 

passive wind transport. Attaphila living in the fungus 

gardens of leaf-cutting ants have apterous females and 

brachypterous or apterous males (Gurney, 1937; Roth, 

1991a). Both Att. fungicola and Att. bergi have evolved a 

unique solution for moving between nests—they are 

phoretic on ant alates leaving the nest on their mating 

flight (Fig. 2.11) (Wheeler, 1900; Bolívar, 1901; Moser, 

1964; Waller and Moser, 1990). These myrmecophiles 

have large arolia (Gurney, 1937) that may assist them in 

clinging to their transport. Several questions arise concerning 

this phoretic relationship. Do both male and 

female cockroaches disperse with the alates, or only fertilized 

females? Since the nuptial flight of male ants is 

invariably fatal (Hölldobbler and Wilson, 1990), do the 

cockroaches choose the sex of their carrier? If cockroaches 

do choose male alates, perhaps they can transfer 

to female alates while the ants are copulating. The vast 

majority of the thousands of released virgin queens die 

within hours of leaving the nest (Hölldobbler and Wilson, 

1990); do their associated cockroaches subsequently 

search for nests on foot? Because they disperse together, 

would molecular analysis reveal a co-evolutionary relationship 

between this myrmecophile and its host? A 

comparison of Attaphila to Myrmecoblatta wheeleri also 

28 COCKROACHES

Fig. 2.11 Phoretic female of Attaphila fungicola attached to the 

wing base of Atta sp. host. The cockroach is about 2.7 mm in 

length. Courtesy of John Moser. 

would be of interest. The latter lives in the nests of a variety 

of ant genera (Campanotus, Formica, Solenopsis), but 

have no arolia or pulvilli on the tarsi, and there are no 

records of host transport (Fisk et al., 1976). 

Arboreal 

Species that live in trees are generally expected to be good 

fliers, because the alternative is a long down-and-up surface 

trip when moving between limbs or trunks (Roff, 

1990; Masaki and Shimizu, 1995). Fisk (1983) identified 

the cockroaches that fell during canopy fogging experiments 

conducted in rainforests in Panama and Costa 

Rica. Of the 25 species for which wing condition is known 

in both males and females, 23 (92%) are winged in both 

sexes, one (Nesomylacris asteria) has reduced tegmina and 

wings in both sexes, and one (Compsodes deliculatus) has 

winged males and apterous females (analyzed by LMR). 

Small blattellid species were the most abundant and diverse 

group collected during the study. These data support 

the notion that cockroaches that spend the day in 

trees are generally flight-capable. Further support comes 

from behavioral observations in Costa Rica. Flight between 

perches was noted in all winged species observed 

during their active period (Schal and Bell, 1986). Some 

cockroach species, however, spend their entire lives 

within specialized arboreal niches, are unlikely to be collected 

during canopy fogging, and are not necessarily 

volant. These include cockroaches that live under bark, in 

epiphytes, in arboreal litter, and in insect and bird nests. 

Of the 31 species of Brazilian cockroaches collected in 

bromeliads by Rocha e Silva Albuquerque and Lopes 

(1976), 55% were apterous or brachypterous. 

Caves 

As discussed in the following chapter, caves are at one end 

of a continuum of subterranean spaces frequented by 

cockroaches, with the border between caves and other 

such habitats often vague. Variation in wing reduction, as 

well as associated morphological changes, may reflect different 

degrees of adaptation to these specialized habitats. 

In Australian Paratemnopteryx, species found in caves 

usually exhibit some degree of wing reduction (Table 

2.2). Several species in this genus are intraspecifically 

variable; both macropterous and reduced-wing morphs 

of Para. howarthi can even be found in the same cave 

(Roth, 1990b). Epigean species in the genus living under 

bark or in leaf litter are often macropterous, but also may 

exhibit wing reduction. The area of the cave inhabited 

(deep cave versus twilight zone), nutrient availability (is 

there a source of vertebrate excrement?), and length of 

time a population has been in residence all potentially influence 

the morphological profiles of the cave dwellers. 

Like other invertebrates, cockroaches that are obligate 

cavernicoles (troglobites) typically exhibit wing reduction 

or loss. 

Table 2.2. Wing development in cavernicolous and epigean 

species of the Australian genus Paratemnopteryx, based on 

Roth (1990b), Roach and Rentz (1998), and Slaney (2001). 

Those species described as epigean were found under bark 

and in litter. 

Species Habitat Wing condition 

Para. atra Cavernicolous, in Slightly reduced 

mines 

Para. australis Epigean, one record Reduced 

from termite nest 

Para. broomehillensis Epigean Macropterous 

Para. centralis Epigean Macropterous 

Para. couloniana Epigean, in houses Variably reduced, 

some males 

macropterous 

Para. glauerti Epigean Male macropterus, 

female reduced 

Para. howarthi 1 Cavernicolous Macropterous and 

and epigean reduced males, 

females reduced 

Para. kookabinnensis Cavernicolous Reduced 

Para. rosensis Epigean Male macropterous, 

female reduced 

Para. rufa Cavernicolous Reduced 

and epigean 

Para. stonei Cavernicolous and Variably reduced 2 

epigean 

Para. suffuscula Epigean Macropterous 

Para. weinsteini Cavernicolous Reduced, female 

more so 

1 

Brachypterous and macropterous morphs can be found in same cave. 

2 

Female wings slightly longer than male’s. 


Wing Variation within Closely Related Groups 

A number of closely related cockroach taxa unassociated 

with caves can show as much variation as Paratemnopteryx. 

Wing condition is therefore of little value as a diagnostic 

generic character unless it occurs in conjunction 

with one or more stable and distinctive characters 

(Hebard, 1929; Rehn, 1932b). The three native species of 

the genus Ectobius in Great Britain clearly depict an evolutionary 

trend in female wing reduction. Males are 

macropterous in all three species. Females of E. pallidus 

also have fully developed wings, but in E. lapponicus the 

tegmina of the female are about two-thirds the length of 

the abdomen and the wings are reduced. In E. panzeri the 

tegmina of the female are just a little longer than wide and 

the wings are micropterous (Kramer, 1956). The subfamily 

Tryonicinae illustrates the degree of wing variation 

that can occur at higher taxonomic levels. Table 2.3 displays 

the genera of these blattids arranged to exhibit a detailed 

gradient of wing development from one extreme 

(macropterous) to the other (apterous). 

Case Study: Panesthiinae 

Those members of the Panesthiinae for which we have 

ecological information are known to burrow in soil 

(Geoscapheini) or rotted wood (the remainder). They 

therefore illustrate the range of wing variation possible 

within an ecologically similar, closely related taxon (Table 

2.4). Many species in the subfamily have fully developed 

tegmina and wings, and are heavy bodied but able flyers 

(Fig. 2.12A). Male Panesthia australis, for example, have 

been collected at lights in Australia (Roth, 1977; CAN, 

pers. obs.). Some genera include sexually dimorphic 

species, with winged males and wingless females (Miopanesthia), 

and a number of species in the genus Panes- 

Fig. 2.12 Wing condition in wood-feeding Panesthiinae. (A) 

Fully winged adult of Australian Panesthia australis; photo by 

C.A. Nalepa; (B) detail of adult Australian Panesthia cribrata 

showing ragged wing bases after dealation; photo courtesy 

of Douglas Rugg; (C) strikingly patterned winged female of 

Caeparia donskoffi from Vietnam, body length approximately 

3.5 cm; photo by L.M. Roth. 

Table 2.3. Tryonicinae (Blattidae) illustrate the complete range of wing development, from fully developed wings to completely 

apterous, with intermediate stages (LMR, pers. obs.). 

Genus 

Wing characters (no. species) Country 

Fully winged, but wings may not reach the end of the abdomen Methana (10) Australia 

Tegmina reduced, elongated, lateral, completely separated from the mesonotum, Tryonicus (3) Australia 

reaching a little beyond hind margin of second abdominal tergite, hindwings present, (female apterous) 

vestigial, lateral, completely covered by the tegmina 

Tegmina small, lateral lobes completely separated from the mesonotum, Punctulonicus (2) New Caledonia 

not reaching the first abdominal tergite, wings absent Angustonicus (2) 

Rothisilpha (2) 

Tegmina lateral, but not completely separated from the mesonotum, wings absent Pellucidonicus (2) New Caledonia 

Pallidionicus (5) 

Angustonicus (1) 

Punctulonicus (1) 

Rothisilpha (1) 

Completely apterous Lauraesilpha (4) New Caledonia 

30 COCKROACHES

Table 2.4. Extent of development of tegmina and wings in 10 genera of Panesthiinae; after Table 6 in Roth (1982b).The “reduced” wing 

category includes brachypterous morphs, micropterous morphs, and those with reduced tegmina and absent wings. One genus 

includes polymorphic species (Panesthia). Sexual dimorphism is found only in the genus Miopanesthia. 

Number of species subspecies with tegmina and wings 

Fully 

Fully developed 

developed reduced-wing 

Genus (macropterous) 1 morphs Reduced Absent Total 

Panesthia 2 23 1 5 1 15 2 11 1 54 9 

Miopanesthia 2 

Male 6 0 0 2 8 

Female 1 3 0 0 7 8 

Ancaudellia 2 15 1 0 3 + 3 0 18 4 

Salganea 2 26 3 0 12 1 4 42 4 

Caeparia 2 4 0 0 0 4 

Microdina 0 0 1 0 1 

Parapanesthia 4 0 0 0 1 1 

Neogeoscapheus 4 0 0 0 2 2 

Geoscapheus 4 0 0 0 2 2 2 2 

Macropanesthia 4 0 0 0 4 4 

1 

A number of these eventually shed their wings. 

2 

Wood-feeding cockroaches; information on the diet of Miopanesthia, Caeparia, and Ancaudellia from a pers. comm. from K. Maekawa to CAN. 

3 

The original description of M. sinica Bey-Bienko did not indicate the wing condition of the female; the implication is that they have tegmina and wings 

(Roth, 1979c). 

4 

Soil-burrowing cockroaches (Geoscapheini). 

thia are intraspecifically variable. Of these, both males 

and females may have either well-developed or variably 

reduced wings. In some species (e.g., Pane. australis), the 

reduced-wing form is uncommon (Roth, 1977). 

Uniquely among cockroaches, some macropterous 

members of this subfamily shed their wings. In some 

species of Panesthia, Salganea, and Ancaudellia only the 

basal region of the tegmina and wings remains intact. The 

wings are not cleanly snapped at a basal suture, as in termites, 

but have a raggedy, irregular border (Fig. 2.12B) 

(Roth, 1979c; Maekawa et al., 1999b). Some early observers 

thought that dealation resulted from the chewing 

action of conspecifics (Caudell, 1906), that they “solicit 

the assistance of their comrades to gnaw them off close to 

the base.” Others, however, suggested that the wings were 

broken off against the sides of their wood galleries, because 

dealation occurs even in isolated individuals and 

because the proposed gnawing action was never observed 

(McKeown, 1945; Redheuil, 1973). The wings are most 

likely lost by a combination of both behaviors. In laboratory 

studies of Panesthia cribrata, Rugg (1987) saw adults 

moving rapidly backward, rubbing the wings against the 

sides of the cage, and also observed a male chewing the 

wing of a female, then dragging off a tattered portion and 

eating it. Rugg illustrates obviously chewed wings, with 

distinct semicircular portions removed. Individuals are 

unable to chew their own wings (D. Rugg, pers. comm. to 

CAN). Like termites and some other insects, Panesthiinae 

with deciduous wings restrict flight activity to the prereproductive 

stage of their adult life. It would therefore be 

of interest to determine if flight muscle histolysis accompanies 

wing loss, and if so, how it relates to fecundity. In 

crickets, dealation induces histolysis of the wing muscles 

and a correlated rapid production of eggs (Tanaka, 1994). 

A well-corroborated estimate of relationships among 

20 species of Panesthiinae inferred from a combined 

analysis of 12S, COII, and 18S is illustrated in Fig. 2.13 

(Maekawa et al., 2003). We mapped four wing-related 

character states onto the depicted tree: wing morphology 

(macropterous, reduced wings, or apterous), and in 

macropterous species, whether the wings are permanent 

or deciduous. The apterous condition appears to have 

evolved three times, in Miopanesthia deplanata, Panesthia 

heurni, and the Geoscapheini. Deciduous wings arose 

twice, in Salganea and in the lineage that includes 

Panesthia and Ancaudellia. Within Salganea, reduced 

wings seem to be derived from the macropterous, deciduous 

state. Maekawa et al.’s (2003) phylogeny is not fully 

resolved and shows the genus Panesthia as poly- or paraphyletic. 

It is nonetheless obvious that the morphological 

wing condition and the behaviors associated with removing 

deciduous wings are evolutionarily labile in these 

cockroaches. Wings are generally dull and uniformly colored 

in the Panesthiinae that eventually shed them. Un- 


Fig. 2.13 Phylogenetic distribution of wing condition in the Panesthiinae. The phylogenetic tree 

is inferred from a combined analysis of 12S, COII, and 18S, obtained using Bayesian inference of 

phylogeny with the GTR I G model of substitution. Posterior probabilities (PP), expressed 

as percentages, are shown above branches to indicate the level of support for each node. Branches 

with less than 50% PP were collapsed to form polytomies. Bootstrap values (expressed as percentages) 

from an MP analysis are shown below the nodes. The asterisk indicates a node that was 

not supported in more than 50% of bootstrap replicates; however, an analysis in which COII third 

codon transitions were downweighted by a factor of 4 resulted in 70% support. The scale bar indicates 

the number of inferred substitutions per site. From Fig. 3 (p. 1305) in Maekawa et al. 

(2003), courtesy of K. Maekawa and with permission of the Royal Society of London. Wing conditions 

based on Roth (1979b, 1979c) and the observations of K. Maekawa (pers. comm. to CAN). 

like the other macropterous species, Panesthia transversa 

and Caeparia crenulata (as well as other species of Caeparia) 

have strongly colored and patterned wings and retain 

them throughout their adult life (Fig. 2.12C). This reinforces 

the idea that cockroach wings have functional 

significance in contexts other than flight; in this case it is 

likely that retained wings have signal value to predators, 

conspecifics, or both. A comparison of the population genetics 

of apterous or brachypterous wood-feeding species 

to those that have remained flight capable might yield 

data relevant to dispersal distances. 

Intraspecific Wing Variation 

A similar reduction in tegmina and wings often occurs in 

both sexes of a species. Sexual dimorphism is common, 

however, and it is most often the female that exhibits the 

greater degree of wing reduction. At one extreme are 

species with fully winged males and apterous females. 

Examples include the African genus Cyrtotria ( Agis) 

(Rehn, 1932a), Trichoblatta sericea, living on and under 

the bark of Acacia trees in India (Reuben, 1988), and 

many desert Polyphagidae. In A. investigata, for example, 

females are wingless, but at night fully winged males 

emerge from the sand and fly (Edney et al., 1974). Females 

of Escala circumducta have “almost discarded their organs 

of flight” and live their entire lives beneath the bark of 

trees. The fully winged males associate with the females 

only during a brief pairing season (Shaw, 1918). In cockroaches 

with extreme wing dimorphism females are often 

burrowers or crevice fauna, but the habitats of males are 

unknown, because they have been collected only at lights. 

Some cases of sexual dimorphism are so extreme that 

they are problematic to taxonomists trying to associate 

the two sexes (Roth, 1992). Females of Laxta ( Onisco- 

32 COCKROACHES

soma) granicollis are flattened and wingless, resembling 

“an enormous wood louse,” while males are winged and 

“of more graceful shape” (Swarbeck, 1946). Similarly, 

males of several species of Perisphaeria and Pseudoglomeris 

are slender, winged insects, while the females are 

apterous and broader (Hanitsch, 1933). More moderate 

cases of wing dimorphism include species where both 

sexes have reduced wings but the female more so, and 

those species discussed above, where both sexes are fully 

winged, but the female is nonetheless flightless. We are 

not aware of cases of macropterous females and apterous 

males, but when wing reduction occurs in both sexes, 

sometimes the wings of the male are shorter (e.g., Para. 

stonei—Roth, 1990b). 

Wing development within a species is not always a 

fixed character. In some cockroaches, only one sex exhibits 

variation, for example, Neotemnopteryx fulva males 

are macropterous, but the females may be macropterous 

or brachypterous (Roth, 1990b). Likewise, E. africanus 

males are macropterous, but female wing reduction 

varies with altitude (Rehn, 1932b). In other cockroaches, 

the reduction of tegmina and wings is variable in both 

sexes. These include at least five species of Panesthia 

(Roth, 1982b), H. concinna in the Galapagos (Roth, 1990a), 

and the Australian Para. couloniana (Roth, 1990b). The 

latter generally has brachypterous tegmina and micropterous 

wings, but the degree of reduction varies, and 

there are males whose flight organs are fully developed. 

This species lives in litter and under bark, but there are 

also records of it infesting houses (Roach and Rentz, 

1998). 

Migration 

Intraspecific variation in the wing form of insects is usually 

associated with migratory flight, that is, dispersal or 

migration from the habitat, as opposed to trivial flight, 

activity associated with routine behavior such as feeding, 

mate finding, or escaping from enemies. As such, the environmental 

cues known to influence wing form are those 

that signal seasonal habitat deterioration (photoperiod, 

temperature) or less predictable, density-dependent habitat 

changes (poor nutrition, stress, crowding) (Travis, 

1994; Masaki and Shimizu, 1995). High population density 

is known to induce a number of morphological and 

physiological changes in studied cockroach species, for 

example, Blab. craniifer (Goudey-Perriere et al., 1992) 

and Eublaberus distanti (Rivault, 1983), but to date, wing 

form has not been one of them. 

Mass migrations and dispersals have been recorded in 

cockroaches, though not in wing-polymorphic species. 

Surface activity in C. punctulatus occurs following rainfall, 

during daylight hours in spring (Nalepa, 2005). Soilburrowing 

Australian Geoscapheini undertake spectacular 

pedestrian migrations after rains—sometimes seen by 

motorists crossing roads every few yards for 32 km at a 

stretch (Monteith, pers. com. to LMR). There are two intriguing 

reports of possible long-distance movement by 

flight. On a sunny morning in Venezuela at an elevation 

of 1100 m, Beebe (1951) observed a “flurry” of at least 30 

Blaberus giganteus fluttering slowly up a gorge used as a 

flyway for migrating insects. Under the hot sun in an 

Arizona desert, Wheeler (1911) watched two separate 

swarms of male Homoeogamia subdiaphana alternately 

flying and quickly running over the sand in a southwesterly 

direction; he likened their quick movements to those 

of tiger beetles (Cicindelidae). Overpopulated buildings 

or sewers have been known to spawn natural migrations 

in several species of urban pests (Roth and Willis, 1957). 

It is unusual that many of these movements occur during 

daylight hours in otherwise nocturnal insects. Stein and 

Haschemi (1991) report that German cockroaches emigrating 

from a garbage dump used solar cues for orientation. 

Most walked directly toward the sun, with their 

bearing shifting from east to west over the course of the 

day. 

Evolution of Flightlessness 

Macropterism is clearly the primitive condition in cockroaches 

(Rehn, 1932b). Because no fossil cockroaches are 

known with abbreviated organs of flight (R.J. Tillyard, in 

Shaw, 1918), it is assumed that Paleozoic cockroaches 

were swift-flying and diurnal (Brodsky, 1994). Flight may 

have been advantageous in Carboniferous swamps, as it 

would allow movement between patches of habitat surrounded 

by water. On the other hand, the possession of 

wings does not assure the ability to fly, and apterous and 

brachypterous cockroaches are less likely to leave fossil 

evidence than their more volant relatives. There are indications 

of wing sexual dimorphism in the fossil record. 

Schneider (1977, 1978) concluded that the wings of Carboniferous 

females were broader than those of males, and 

Laurentiaux (1963) demonstrated that there were intersexual 

differences in both the length and the shape of 

wings. 

It is possible to induce alary reduction experimentally 

in a normally winged species (e.g., Blab. craniifer), but attempts 

to produce fully developed wings in an apterous 

cockroach have been unsuccessful; Lefeuvre (1971) therefore 

concluded that the evolutionary loss of wings is irreversible. 

On the other hand, Masaki and Shimizu (1995) 

suggested that wing reduction is possible without elimination 

of the genetic background for macropterous development, 

and potential evolutionary reversal of wing 

loss has been demonstrated in the Hemiptera-Heter- 


optera (Anderson, 1997) and in the Phasmatodea (Whiting 

et al., 2003). As robust phylogenetic trees become 

available for varying cockroach taxa, the possibility of the 

re-evolution of wings in the Blattaria can be put to the 

test. 

Habitat Factors Associated with Wing Loss 

Flight loss in insects is most often associated with environmental 

stability (Southwood, 1962; Harrison, 1980; 

Roff, 1990; Denno et al., 1991, 2001b; Wagner and Liebherr, 

1992; Zera and Denno, 1997, among others). The 

logic is that flightless morphotypes are inclined to persist 

in spatially homogeneous, temporally stable habitats 

where food, shelter, and mates are continuously accessible 

to pedestrians. Conversely, flight is retained in insects 

living in temporary habitats, so that fluctuating levels 

of resource quality and abundance may be tracked. Although 

a number of studies support this hypothesis (e.g., 

Roff, 1990; Denno et al., 1991), the association of cockroaches 

with their habitat is not as clear as it is in insects 

such as stenophagous herbivores on annual plants, or 

waterstriders that live in temporary versus permanent 

ponds. Few cockroaches are exclusively associated with 

ephemeral or periodically disturbed habitats, although 

they may utilize them if available. Some species exhibit 

seasonal habitat shifts, but there are no known cockroaches 

with seasonal variation in wing morphology. 

Several hurdles to understanding the role of habitat in 

structuring cockroach wing morphology must be added 

to those noted earlier. First, there can be a great deal of intraspecific 

variation in habitat choice. A good example is 

Chorisoneura carpenteri from the Galapagos, a species 

with both brachypterous and macropterous forms. The 

fully winged morphs have been collected at elevations of 

30–1000 m in agricultural areas, arid zones, pampa, humid 

forest, and Scalesia forest; the brachypterous form 

has been collected at 120–700 m in all of the listed habitats 

but one—the agricultural zone (Peck and Roth, 

1992). Second, many cockroaches defy being described by 

just one aspect of their habitat, and it is difficult to tease 

apart the relative importance of a hierarchy of overlapping 

ecological levels. Is a canopy cockroach more likely 

to be wingless if the forest is on a mountain? Is it valid to 

compare a list of wingless cockroaches found in caves to 

a list of wingless cockroaches found in Texas (Roff, 1990, 

p. 395)? Finally, the fact that so many cockroaches in different 

habitats utilize the same microhabitats confounds 

analysis. Whether they are found in a desert, grassland, 

forest, or elsewhere, many cockroaches are associated 

with a continuum of dark, humid, enclosed spaces that 

they find or make. 

The strength of the association of a given cockroach 

species with these subterranean and other spaces appears 

influential in wing development. Cockroaches that live 

their entire lives in burrows, galleries, or crevices, except 

for a brief dispersal period at the subadult or young adult 

stage or when the habitat becomes unsuitable, seem most 

prone to winglessness. It is apparent from an examination 

of the Panesthiinae (Fig. 2.13) that the habit of burrowing 

in wood or soil may be connected to the prevalence of 

reduced, absent, or deciduous wings in this subfamily. 

Cockroach species that spend their lives in the loose 

spaces beneath bark also fall into this category. Shaw 

(1918) noted that flightless cockroaches are generally 

cryptic in their habits, and that there was a “definite correlation” 

between a flattened morphology and the absence 

of wings. In deserts, cockroach microhabitats include 

the base of grass tufts and the spaces beneath debris 

and boulders. The majority of desert cockroaches, however, 

live a partially or entirely subterranean existence. 

Half of the 28 desert cockroaches listed by Roth and Willis 

(1960) live in the burrows of small vertebrates, and additional 

species burrow into loose sand. It should be noted 

that obligate cavernicoles are an extreme case of this same 

continuum. The ecological influences that promote wing 

loss in all these cockroaches, then, may differ more in degree 

than in type. 

Several characteristics of crevices and burrows may influence 

wing loss in the cockroaches that permanently or 

periodically inhabit them. First, these are temporally stable 

habitats. Logs, leaf litter, and other rotting vegetable 

matter are continuously or periodically replenished from 

source plants, and migration to fresh resources, if required, 

is often a local trip. Second, these are homogeneous 

microhabitats, in that they are interchangeable 

dark, moist, protected quarters. If leaf litter on the forest 

floor loses moisture during the tropical dry season, for example, 

cockroaches normally found in ground-level litter 

are known to move into moist, arboreal accumulations of 

leaves (Young, 1983). Third, these are chiefly two-dimensional 

microhabitats, particularly for cockroach species 

that either rarely venture from shelters or have a modest 

ambit around them. Schal and Bell (1986) found that 

many of the flightless cockroach species in Costa Rican 

rainforest ground litter did not move very far in vertical 

space during their active period. Recent evidence suggests 

that it is the interaction of habitat dimensionality and 

habitat persistence that may have the most significant effect 

on insect wing morphology (Waloff, 1983; Denno et 

al., 2001a, 2001b). Finally, these cockroaches are able to 

feed within their shelter (in logs, under bark, in leaf litter, 

in vertebrate burrows, in social insect nests, in caves), or 

the shelters are situated in the immediate vicinity of potential 

food (soil burrowers, under rocks, under logs). 

The proximity of widespread, persistent, often abundant 

34 COCKROACHES

ut low-quality food has two potential implications for 

the evolution of cockroach wing morphology. First, the 

insects are less tied to the seasonality of their food source. 

Flightlessness in insects tends to be positively correlated 

with their ability to remain throughout the year in their 

developmental habitat (Anderson, 1997; Denno et al., 

2001a). Second, wing reduction and loss is often associated 

with nutrient limitation (Jarvinen and Vepsalainen, 

1976; Kaitala and Hulden, 1990), and cockroaches that 

rely on rotting vegetable matter as a primary food source 

may be living close to their nutritional threshold. In caves, 

wing loss and associated morphological changes occur 

more frequently in organisms that rely on plant debris 

than those that rely on bat or bird guano (Culver et al., 

1995). 

Wing Loss and Life History Trade-offs 

Food abundance and quality cannot be divorced from 

wing morphology because it is costly to produce and 

maintain the wings and their muscular and cuticular support 

(Roff and Fairbairn, 1991); insect flight muscle is 

one of the most metabolically active tissues known (e.g., 

Weis-Fogh, 1967). Flight behavior is also energetically demanding, 

and can alter the composition of hemolyph for 

up to 24 hr afterward in P. americana (King et al., 1986). 

These metabolic expenses place a significant demand on 

an insect’s overall energy budget, and compete with other 

physiologically demanding life history processes. The 

best documented of these is egg production. Any easing 

of the selective pressure to maintain wings allows a female 

to divert more resources to egg production, increasing her 

fitness more than if she remained volant (“flight-oogenesis 

syndrome”) (Roff, 1986, 1990; Roff and Fairbairn, 

1991). Flight capability can diminish rapidly under the 

right conditions (Denno et al., 1991; Marooka and Tojo, 

1992), and may account for the lack of functional flight 

muscle in laboratory-reared females of Periplaneta (Table 

2.1). The flight-oogenesis syndrome also may account for 

the prevalence of flightless females, rather than males, in 

cockroach species exhibiting sexual dimorphism in flight 

ability. The relationship between wing morphology and 

fecundity has been demonstrated in a number of insect 

species, including orthopteroids (e.g., Cisper et al., 2000), 

but is as yet unstudied in cockroaches. The fact that there 

are numerous cockroach species with males possessing 

reduced or absent wings suggests that there is a cost to the 

retention of wings even in males. In some insects, shortwinged 

males have a mating advantage over macropterous 

males, or a gain in testes and body size (Dingle, 1996; 

Langellotto et al., 2000). Macroptery in males is most often 

related to the distribution of females in the habitat, 

and whether they are accessible to males on foot (Roff, 

1990; Denno et al., 2001a). This is likely the case in cockroaches, 

because in many species females produce volatile 

sex pheromones; males use these chemical cues to actively 

seek mating partners (Gemeno and Schal, 2004). The degree 

of wing development may affect longevity in both 

sexes (Kaitala and Hulden, 1990; Roff and Fairbairn, 

1991). It may be relevant, then, that among the longestlived 

of the known cockroaches are apterous species that 

burrow in wood or soil (Chapter 3). 

Wing Loss, Paedomorphosis, 

and Population Structure 

A lack of functional wings is at the heart of two obstacles 

to understanding the evolutionary biology of some earthbound 

cockroaches. First, aptery and brachyptery are 

associated with a developmental syndrome that reduces 

morphological complexity, making it difficult to distinguish 

among closely related taxonomic groups. Second, 

the loss of mobility associated with aptery can result in 

complex geographic substructuring of these morphologically 

ambiguous groups. 

Wing reduction or loss is the best indicator of paedomorphosis, 

defined as the retention of juvenile characters 

of ancestral forms in the adults of their descendents 

(Matsuda, 1987; Reilly, 1994). Not all short-winged insects 

retain juvenile characters, but in other cases, it is 

clear that many so-called adult characters are absent in 

short-winged or apterous morphs (Harrison, 1980). The 

diminishment or loss of structures such as ocelli, compound 

eyes, antennal and cercal segments, and some integumental 

structures such as sensilla often accompanies 

aptery and brachyptery (Matsuda, 1987). These reductions 

are common in cockroaches (Nalepa and Bandi, 

2000), and like other animals (Howarth, 1983; Juberthie, 

2000b; Langecker, 2000) occur most often in species that 

inhabit relatively safe, stable environments, such as caves, 

burrows, logs, social insect nests, leaf litter, and other 

cryptic environments. Lefeuvre (1971) found that some 

cockroach species with reduced wings have fewer developmental 

stages than macropterous relatives, and that juvenile 

features can be retained in the tracheal system, peripheral 

nervous system, and integument. Warnecke and 

Hintze-Podufal (1990) concluded that the reduced wings 

of female Blaptica dubia are the result of larval characters 

that persist into maturity, rather than the growth inhibition 

of adult wings. Other examples include the retention 

of styles in wingless adult females of Noc. termitophila (female 

cockroaches normally lose their styles prior to the 

adult stage) (Matsuda, 1979), and the reduced sensory 

and glandular systems of the myrmecophile Att. fungicola 

(Brossut, 1976). Cryptocercus has reduced eyes and cercal 

segmentation, and exhibits marked paedomorphic traits 


in its genital morphology (Walker, 1919; Crampton, 

1932; Klass, 1995). Females of the desert cockroach A. investigata 

are “generally nymphlike,” lack the wings and 

ocelli seen in the male, and have shorter antennae and 

cerci (Friauf and Edney, 1969). Because wing loss in cockroaches 

is female biased, it is most often females that exhibit 

correlated paedomorphic characters. 

The systematics of paedomorphic organisms can be 

frustrating. Because many structures never develop or 

develop variably within a group, they cannot be used to 

delimit taxa, or to infer phylogenetic relationships. Independent 

losses of ancestral postmetamorphic features is 

an important source of homoplasy and can confound 

cladistic analysis (Wake, 1991; Brooks, 1996; Hufford, 

1996). The morphological homogeneity of the Polyphagidae 

has caused quite a few problems with attribution, 

not only to species but also to genera (Failla and 

Messina, 1987). Members of the genus Laxta “vary so 

much in color and size and have genitalia so similar as to 

make distinguishing taxa difficult” (Roth, 1992). Paedomorphic 

characters and mosaic evolution in the woodfeeding 

cockroach Cryptocercus strongly contribute to 

problems in determining the phylogenetic relationships 

of this genus at all taxonomic levels (Klass, 1995, 1998a; 

Nalepa and Bandi, 1999, 2000; Nalepa et al., 2002). Cave 

cockroaches, like other cave dwellers (Howarth, 1983; Juberthie, 

2000a; Langecker, 2000), are prone to taxonomic 

problems associated with paedomorphosis. Roth (1990b) 

noted that Para. stonei from different caves all had reduced 

hindwings but varied in body size, in the development 

of pulvilli, and in length of tegmina. The genitalia 

were so similar, however, that he assigned them to different 

races within the species. A morphometric study by 

Slaney and Weinstein (1997b) subsequently supported 

Roth’s conclusions. 

Molecular and chemical tools are increasingly required 

to provide characters to distinguish among these morphologically 

ambiguous cockroach taxa. Humphrey et al. 

(1998), for example, used protein electrophoresis to propose 

that morphologically similar populations of M. rhinoceros 

are comprised of three genetic species. Slaney and 

Blair (2000) used the ITS2 gene region of nuclear ribosomal 

DNA in the Para. stonei group, and their results 

supported conclusions based on morphology. Molecular 

phylogenetic relationships, however, are not always completely 

congruent with relationships based on morphological 

characters. Basal relationships among species of 

the wood-feeding blaberid Salganea are poorly resolved 

by molecular analysis, probably because of rapid and potentially 

simultaneous radiation of the group (Maekawa 

et al., 1999a, 2001). 

In flightless animals the pool of potential mating partners 

is limited to those that can be found within walking 

distance, resulting in restricted levels of gene flow. Populations 

may become subdivided and isolated to varying 

degrees, resulting in complex genetic substructuring and 

the formation of local species, subspecies, and races. This 

is common in caves, where subterranean spaces can be 

isolated or locally connected via mesocaverous spaces 

(Barr and Holsinger, 1985). It is also common on mountains, 

where endemic races and subspecies may be wholly 

restricted to single peaks (Mani, 1968). Cryptocerus primarius, 

for example, is found in an area of China with a 

dissected topography characterized by high mountain 

ridges sandwiched between deep river gorges, forming 

various partitioned habitats (Nalepa et al., 2001b). This 

genus of montane cockroaches is also dependent on rotting 

logs, which ties their distribution to that of mature 

forests. Any event that has an impact on the distribution 

of forests, including glaciation (Nalepa, 2001; Nalepa et 

al., 2002) and deforestation (Nalepa et al., 2001b) will affect 

the population structure of the cockroach. Consequently 

the geographic distribution of genetic populations 

and species groups in both Northeast Asia (Park et 

al., 2004; Lo et al., 2000b) and the eastern United States 

(Nalepa et al., 2002) can be unexpected. Cryptocercus 

found in southern Korea, for example, are more closely 

related to populations in Northeast China than they are 

to all other Korean members of the genus. 

36 COCKROACHES

THREE 

Habitats 

Of no other type of insect can it be said that it occurs at every horizon where insects 

have been found in any numbers. 

—S.H. Scudder, “The Cockroach of the Past” 

Cockroaches are found in nearly all habitats: tropical and temperate forests, grasslands, 

heath, steppe, salt marshes, coastal communities, and deserts. They are active in the entire 

vertical dimension of the terrestrial environment, from the upper forest canopy to 

deep in the soil, and inhabit caves, mines, hollow trees, burrows, and sub-bark spaces. 

They are also found in dead leaves, rotting logs, streams and stream edges, epiphytes, arboreal 

water pools, the nests of social insects, rodents, reptiles, and birds, and humanmade 

structures such as dwellings, ships, and aircraft (Roth and Willis, 1960). Cockroaches 

occur between latitudes 60N and 50S, but most are found between 30N and 

30S in the warm, humid regions of the Old World (Africa) and tropical America 

(Guthrie and Tindall, 1968); they are less diverse in the temperate regions. Wolda et al. 

(1983) cites the number of species captured at various latitudes in Central and North 

America: 64 in Panama, 31 in Texas, 14 in Illinois, 9 in Michigan, 5 in Minnesota, and 2 

in North Dakota. In the high arctic, pest cockroaches readily invade heated structures 

(Beebe, 1953; Danks, 1981), but several species are physiologically capable of dealing with 

extremely cold weather in their natural environment (e.g., Celatoblatta quinquemaculata—Worland 

et al., 2004). The general tendency is to live near sea level, where temperatures 

are higher (Boyer and Rivault, 2003). In his collections on Mt. Kinabalu in Borneo, 

Hanitsch (1933) found 19 cockroach species up to an altitude of 2135 m, but only 

three species above it. Light trap catches in Panama also indicate higher diversity in lowland 

than in mountain sites (Wolda et al., 1983). In Hawaii, Allacta similis was found no 

higher than 1600 m along an altitudinal transect and was thought to be excluded from 

higher altitudes by the cooler, wetter, montane environment (Gagné, 1979). Nonetheless, 

the relationship of cockroaches with altitude can be complex. On Volcán Barva in Costa 

Rica, no cockroaches were found at the lowest elevation sampled (100 m), but they were 

present at all other elevations (Atkin and Proctor, 1988). There are also montane specialists, 

such as Eupolyphaga everestiana on Mount Everest at 5640 m (Chopard, 1929). 

37

Fig. 3.1 Occupation of different habitats by cockroaches in a reserve near the town of Welaka 

in northeastern Florida. Of the habitats examined, only four contained no cockroaches: ponds, 

lawns, and dry and moist sparsely vegetated sand. Based on information in Friauf (1953). 

HABITAT SPECIFICITY 

Sorting out habitat specificity in a secretive taxon like 

cockroaches is a daunting task. Although some species are 

known to be habitat specific and have associated morphological, 

physiological, behavioral, and life history 

modifications, many are much more flexible in their living 

conditions. Of 19 examined habitats that contained 

cockroaches in a reserve in northeastern Florida, Parcoblatta 

virginica, Parc. lata, and Arenivaga floridensis were 

each found in just one habitat, and five cockroach species 

were found only in structures (Fig. 3.1) (Friauf, 1953). 

Cariblatta lutea, on the other hand, was found in 15 of 

the habitats, and nymphs of this species have also been 

recorded from the burrows of small vertebrates (Hubbell 

and Goff, 1939). In Jamaica Car. lutea is found in leaf litter, 

under debris of every kind, in dead agaves, and in 

bromeliads (Hebard, 1916a). Even closely related cockroaches 

may vary widely in habitat choice (Table 3.1), 

making the detection of phylogenetic trends problematic. 

ONTOGENY OF HABITAT USE 

Although nymphs generally live in the same habitats as 

adults (Mackerras, 1970), there are several cockroach 

species that exhibit ontogenetic niche shifts. The most 

common pattern is that of females, female-nymph combinations, 

and groups of young nymphs reported from 

burrows, shelters, and other protected sites, often in or 

near a food source. These sheltered sites serve as nurseries, 

with the habitat of youngest nymphs determined 

by the partition 3 behavior of the mother; subsequently, 

nymphs may or may not disperse from their natal area. In 

all species of Gyna, for example, adults are found primarily 

in the canopy, while nymphs are found at ground 

level, often burrowing in the dust of treeholes, abandoned 

insect nests, and caves (Corbet, 1961; Grandcolas, 1997a). 

Juveniles of Capucina patula are restricted to the habitat 

beneath loose bark of live or fallen trees; adults are occasionally 

seen on nearby foliage (WJB, pers. obs.). Nymphs 

of Car. lutea, and females and nymphs of Parcoblatta fulvescens 

have been recorded from the burrows of pocket 

gophers (Geomys sp.) (Hubbell and Goff, 1939). Adults of 

both these species are found in a variety of above-ground 

habitats. Adults of Parcoblatta bolliana are found in grass- 

3. Partition is defined as the expulsion by the female of the reproductive 

product, whether it is an egg or a neonate (Blackburn, 

1999). 

38 COCKROACHES

Table 3.1. New World distribution and microhabitats of 

Latiblattella (Blattellidae). From Willis (1969). 

Species Habitat Country 

Latiblattella inornata Decaying leaf mold Canal Zone 

and litter under 

palms 

Lat. chichimeca In bromeliads Mexico 

Lat. zapoteca Under stones at the Costa Rica 

edge of rivers 

Lat. rehni In Spanish moss Florida 

(Tillandsia usueoides), 

under bark of dead pines 

Lat. lucifrons On Yucca elata Arizona 

Lat. angustifrons On Inga spp. trees Costa Rica 

Lat. azteca On grapefruit trees Mexico 

Lat. vitrea In dry, curled leaves Mexico, 

of corn plants (Zea zea) Costa Rica, 

Honduras 

1996a). In wood-feeding cockroaches, juvenile food and 

habitat is set when the parent chooses a log to colonize. 

The horizontal distribution of cockroaches in caves is often 

related to the resting positions of bats, which determine 

the placement of guano and other organic matter. 

Gautier (1974a, 1974b) calculated the spatial distribution 

of burrowing Blaberus nymphs in caves by counting the 

number of individuals in 50 cm 2 samples to a depth of 15 

cm. He found that nymphs were concentrated in zones 

where bat guano, fruit, and twigs dropped by the bats 

accumulated, and were absent from zones of dry soil, 

stones, or pebbles. In many cave cockroaches, females descend 

from their normal perches on the cave walls to 

oviposit or give birth on the cave floor in or near guano 

(e.g., Blaberus, Eublaberus, Periplaneta—Crawford and 

Cloudsley-Thompson, 1971; Gautier, 1974b; Deleporte, 

1976), where the nymphs remain until they are at least 

half grown. They then climb onto the cave walls, where 

they complete their development. 

CIRCADIAN ACTIVITY 

lands, shrub communities, and woods, where they are 

associated with leaf litter and loose bark. Early instars, 

however, are consistently found living in nests of Crematogaster 

lineolata, an ant that inhabits the soil beneath 

large rocks (Lawson, 1967). Females, nymphs, and oothecae 

of Escala insignis have been collected from ant 

colonies in Australia, but males live in leaf litter (Roth, 

1991b; Roach and Rentz, 1998). In Florida, densities of 

Blattella asahinai nymphs and females bearing oothecae 

are highest in leaf litter of wooded areas; all other adults 

are more diffusely distributed (Brenner et al., 1988). 

SPATIAL DISTRIBUTION 

Many factors influence the spatial distribution of a 

species, and it is difficult to determine whether the 

arrangement of individuals in a habitat is determined by 

one, a few, or the combined action of all of them. Individuals 

may move in response to temporal changes (daily 

rhythms, weather, season), or to fulfill varying needs (dispersal, 

mate finding, etc.) (Basset et al., 2003b). The distribution 

of cockroach individuals is often correlated 

with the proximity of appropriate food sources. In 

sparsely vegetated sites, for example, cockroaches are frequently 

associated with whatever plants (and therefore 

their litter) are present. This includes deserts (Edney et 

al., 1978), alpine zones (Sinclair et al., 2001), and other 

arid or Mediterranean-type habitats such as southwestern 

Australia, where the number and diversity of grounddwelling 

cockroaches depends on the type, percent cover, 

and depth of the litter present (Abenserg-Traun et al., 

Many species exhibit daily and seasonal movements in response 

to their dietary, reproductive, and microenvironmental 

needs; these vary with the individual, sex, developmental 

stage, species, day, season, and habitat. Activity 

patterns are expected to differ, for instance, between those 

cockroaches that forage, find mates, reproduce, and take 

refuge all in the same habitat (in logs, under bark, in leaf 

litter) and those that move daily between their harborage 

and the habitats in which they conduct most other life activities. 

The most common circadian activity pattern 

among the latter is for nymphs and adults to rest in 

harborages during the day, then become active as the sun 

sets. At dusk, adults climb or fly to above-ground perching 

sites (Schal and Bell, 1986), while nymphs confine 

their activities to the leaf litter. Some species are evidently 

active for short periods just after sunset, whereas others 

may be observed throughout the night. Within 60 min after 

sunset, adult males and small nymphs of Periplaneta 

fuliginosa emerge from their harborage, followed by 

medium and large nymphs and adult females. After feeding, 

males climb vertical surfaces, while nymphs and most 

females return to shelter (Appel and Rust, 1986). Males 

also become active earlier than females in Ectobius lapponicus. 

They begin moving in the late afternoon, while 

females and nymphs wait until after sunset (Dreisig, 

1971). In Nesomylacris sp., most females do not become 

active until just before dawn, while males are active 

throughout the night. Females of Epilampra involucris are 

active at both dusk and dawn (Fig. 3.2). With few exceptions, 

temporal overlap among nocturnally active species 

is large. 

HABITATS 39

Fig. 3.2 Circadian activity of three nocturnal and one diurnal cockroach species in Costa Rican 

rainforest. Solid bars are a measure of conspicuousness in the field; open bars indicate locomotor 

activity in an outdoor insectary. Modified from Schal and Bell (1986). 

Not all cockroach individuals are mobile on a nightly 

basis. Kaplin (1996) found that 40% of individuals of the 

desert cockroach Anisogamia tamerlana are active in a 

single summer night. In females, locomotor patterns are 

often associated with the reproductive cycle. In Blattella 

germanica, activity increases when females are sexually 

receptive and peaks during ovarian development. Locomotion 

decreases when she is forming or carrying an 

ootheca (Lee and Wu, 1994; Tsai and Lee, 2000). Nauphoeta 

cinerea females likewise stop locomotor activity 

shortly after mating; activity rhythms begin again after 

partition (Meller and Greven, 1996b). In Rhyparobia 

maderae daily activity gradually decreases in parallel with 

the progressive development of eggs until the level characteristic 

of pregnancy is reached (Engelmann and Rau, 

1965; Leuthold, 1966). This inactivity is correlated with 

a decreased requirement for locating food and mates; 

females rarely forage during gestation. An increase in 

movement prior to partition is associated with locating a 

suitable nursery for forthcoming neonates. In juvenile 

cockroaches activity is correlated with the developmental 

cycle. Blattella germanica nymphs are active during the 

first half of a nymphal stadium. During the last third of 

the stadium, they remain in the harborage and move very 

little (Demark and Bennett, 1994). Cockroaches may also 

“stay home” during adverse weather. The activity of E. 

lapponicus is inhibited by wind (Dreisig, 1971), and Lamproblatta 

albipalpus individuals return to harborage when 

disturbed by heavy rain (Gautier and Deleporte, 1986). 

The distance traveled between shelter and sites of foraging 

and other activity varies from 28 m in field populations 

of Periplaneta americana (Seelinger, 1984) to no 

more than a meter or two in female Macropanesthia rhinoceros 

(D. Rugg, pers. comm. to CAN) and Lam. albipalpus 

(Gautier and Deleporte, 1986). 

There are a number of day-active cockroach species, 

but little is known of their biology. Some, such as Euphyllodromia 

angustata (Fig. 3.3), live in tropical rainforest. 

Others inhabit more arid landscapes; these include 

Fig. 3.3 The diurnal species Euphyllodromia angustata perching 

on a leaf, Costa Rica. Note the dead edges of leaf holes and 

the presence of epiphylls on the leaf surface, both of which are 

included in the diet of many tropical cockroaches. Photo courtesy 

of Piotr Naskrecki. 

40 COCKROACHES

ightly colored Australian species in the blattellid genus 

Ellipsidion, and members of the blattid subfamily Polyzosteriinae 

(Tepper, 1893; Mackerras, 1965a; Rentz, 1996). 

In Platyzosteria alternans, nymphs are diurnal while 

adults are nocturnal (Roach and Rentz, 1998). 

Activity rhythms in cockroaches are controlled by a 

circadian master clock in a region of the brain anatomically 

and functionally connected to the optic system. 

Light entrains the rhythm and allows for synchronization 

with environmental light-dark cycles (Foerster, 2004). An 

absence of cockroach activity rhythms has been observed 

in deep tropical caves, for example, Eublaberus posticus in 

Trinidad (Darlington, 1970), Gyna maculipennis (probably 

Apotrogia n. sp.) in Gabon (Gautier, 1980), but no 

study has demonstrated free-running activity. Blaberus 

colloseus, Blab. atropos, and P. americana positioned close 

to cave entrances become active when the light intensity 

falls below 0.7 Lux (Gautier, 1974a; Deleporte, 1976). 

Adult and older nymphs emerge from their shelters, and 

younger nymphs crawl onto the surface of the cave floor 

at nightfall. An intensity change of 1 Lux influences activity 

rhythms of Blaberus craniifer in the laboratory 

(Wobus, 1966). Observations of cave-dwelling cockroaches 

in Trinidad suggest that activity rhythms also 

may be cued by micrometerological events like wind disturbances 

or an increase in temperature at the beginning 

of bat activity. Darlington (1968) recorded a 2.5C increase 

in temperature in the evening when bats become 

active in the deep part of Tamana Cave. In the laboratory, 

Roberts (1960) found that a thermoperiod with variations 

of 5C was sufficient to set the rhythm of R. maderae 

in continuous darkness. 

VERTICAL STRATIFICATION 

In lowland Costa Rican rainforest individuals space 

themselves in the vertical dimension during their active 

period (Schal and Bell, 1986). There is intersexual and ontogenetic 

variation in the behavior, with males tending to 

perch higher in the vegetation than females (Fig. 3.4). 

This is not simply a function of perch availability, since 

many potential perch sites remain unoccupied. Perch 

height was generally associated with flight ability. Adult 

females of E. involucris, Nesomylacris sp., and Hyporichnoda 

reflexa are either wingless or have very short wings, 

and they perch close to the ground. Epilampra unistilata, 

Xestoblatta hamata, and X. cantralli comprise an intermediate 

group; all are good fliers and after spending the 

day in ground litter, fly to higher perches. The arboreal 

pseudophyllodromiine species (Imblattella n. sp. G, and 

Cariblatta imitans) are excellent fliers and perch higher 

than the intermediate group at night. Except for Imblattella 

spp., early instars are located in ground litter where 

partition occurs; as nymphs develop they gradually perch 

higher in the foliage (Schal and Bell, 1986). 

Vertical stratification during the active period has been 

observed in subtropical and temperate cockroaches as 

well. In the forests and grasslands of eastern Kansas, six 

species (Parcoblatta spp., Ischnoptera spp.) are distributed 

vertically at night among grasses, shrubs, and trees (Gor- 

Fig. 3.4 Vertical distribution of male and female cockroaches during the night in the Costa Rican 

rainforest. Males, open box; females, black box. From Schal and Bell (1986). 

HABITATS 41

ton, 1980). Males are good fliers and are generally located 

higher than females, most of which remain on or near the 

ground. Females seldom fly and, except for Parc. pennsylvanica, 

all have reduced wings. The inability to fly, however, 

is not always correlated with low perch height. Both 

nymphs and brachypterous females of Ectobius sylvestris 

walk on trunks into tree canopies (Vidlička, 1993). 

Cockroaches appear to sort themselves in the vertical 

dimension via their differential sensitivity to zones of temperature, 

humidity, and wind currents (Edney et al., 1978; 

Appel et al., 1983). Schal (1982) found significant differences 

in these variables up to a height of 2 m in the tropical 

forest subcanopy. In one experiment, individually 

marked E. involucris were blinded, then placed at heights 

where they usually do not occur; all individuals migrated 

back to their typical perch zone. This stratification along 

micrometeorological gradients relates to the ascent of 

warm air and pheromone dispersion at night. Females 

emit sex pheromones while perching, and temperature 

inversions carry the pheromones aloft. Males perching 

higher than females would be able to detect rising pheromones 

and locate receptive females. Perching behavior in 

adults, then, is primarily a mate-finding strategy (Schal, 

1982; Schal and Bell, 1986), a conclusion supported by the 

observations of Gorton (1980). Among the temperate 

species he studied in Kansas, males were generally found 

high, females low, and copulating pairs in between. Vertical 

stratification may also be related to communication 

between males and females in desert cockroaches (Hawke 

and Farley, 1973), but data are lacking to support this idea 

or to exclude other explanations. 

SEASONAL ACTIVITY 

Although many cockroach species live in relatively stable 

environments like tropical caves and lowland rainforests, 

others contend with the annual rhythmicity of seasonal 

climates. These include the warm-cold cycles of temperate 

zones and high mountains, and the alteration of wet 

and dry seasons in various tropical habitats. Cockroaches 

cope with environmental extremes and fluctuating availability 

of food in these environs by using varying combinations 

of movement, habitat choice, physiological 

mechanisms, and lifecycle strategies. Cockroaches may 

track food sources, such as those species that move into 

the canopy or beneath particular trees coincident with 

new leaf production or the appearance of spent flowers or 

rotten fruit. In Puerto Rico, for example, branch bagging 

indicated that cockroaches were more abundant on 

Manilkara spp. during the wet season, but on Sloanea 

berteriana during the dry season (Schowalter and Ganio, 

2003). Cockroaches in seasonal environments may move 

into more benign microhabitats during harsh climatic 

conditions, like burrowing into deeper soil horizons or 

litter piles. In summer when their open woodlands habitat 

is excessively dry, Ischnoptera deropeltiformis can be 

found clustered in the damp area beneath recumbent 

portions of sedge-like grass clumps in creek beds (Lawson, 

1967). Logs lying on the soil surface also serve as 

refugia for forest-dwelling cockroaches during dry periods 

(Lloyd, 1963; Horn and Hanula, 2002). Because of 

surface contact with the soil and the concomitant higher 

level of fungal invasion, recumbent logs maintain a 

higher moisture content than standing wood or the top 

layers of the forest floor (van Lear, 1996). Log refugia may 

be particularly important in deciduous forests, where 50– 

70% of incident radiation penetrates to the forest floor 

when trees are in their leafless state, as compared to less 

than 10% when leaves are fully expanded (Archibold, 

1995). Likewise, the spaces beneath stones and logs as well 

as similarly buffered microhabitats may be seasonally occupied. 

In the high alpine zone of New Zealand, individuals 

of Cel. quinquemaculata burrow deep among buried 

rock fragments in winter, but in summer are found under 

surface rocks (Sinclair et al., 2001). In the United Kingdom 

and most of Western Europe, Blatta orientalis can 

survive normal winters outdoors provided it can avoid 

short-term extremes of temperature by choosing suitable 

harborage such as sewers, culverts, and loose soil (le 

Patourel, 1993). Roth (1995b) noted that cavernicolous 

Nocticola brooksi leave the more open caves of western 

Australia as these lose moisture during the dry season. 

Using light trap collections in Panama, Wolda and Fisk 

(1981) demonstrated that cockroaches may show cyclic 

activity even in habitats lacking obvious climatic cycles. 

In both a seasonal and an aseasonal site, adults were most 

common between April and July, corresponding to the 

rainy season in the seasonal site. In follow-up experiments, 

Wolda and Wright (1992) regularly watered two 

plots throughout the dry season on Barro Colorado Island 

in Panama for 3 yr, with two unwatered plots as 

controls. Windowpane traps were used to monitor cockroaches 

and other insects. Forty-six cockroach species 

were captured, with tremendous variation in numbers 

between years. Seasonal variation was also common but 

could not be attributed to the experimental treatment. 

The author concluded that rainfall was not the proximate 

cause of cockroach seasonal activity. Staggered seasonal 

peaks suggested strong interactions among some congeneric 

species (Fig. 3.5) (Wolda and Fisk, 1981). 

Withstanding Cold 

Cockroaches, like other invertebrates, have a diversity of 

responses to cold temperatures (Block, 1991). Each strategy 

entails energetic costs, with many interacting factors, 

42 COCKROACHES

Fig 3.5 The number of individuals of four species of Chromatonotus 

collected per week in a light trap run for 4 yr on 

Barro Colorado Island, Panama. Modified from Wolda and 

Fisk (1981). 

including the minimum temperature to which they are 

exposed, the variation in winter temperature, lifecycle 

stage, body size, habitat, availability of harborage, diet, 

snow cover, and particularly, water requirements and 

management (e.g., Sinclair, 2000). Several temperate 

cockroaches are active throughout winter, including the 

New Zealand species Parellipsidion pachycercum, Celatoblatta 

vulgaris, Cel. peninsularis, and Cel. quinquemaculata. 

The latter is a tiny (adult weight 0.1 g), brachypterous 

cockroach inhabiting alpine communities at altitudes 

greater than 1300 m asl, and is active even when the temperature 

of its microhabitat is below freezing (Zervos, 

1987; Sinclair, 1997). Several North American species of 

Parcoblatta are similarly lively in winter (Horn and Hanula, 

2002). Blatchley (1920) wrote of Parc. pennsylvanica: 

“Cold has seemingly but little effect upon them, as they 

scramble away almost as hurriedly when their protective 

shelter of bark is removed on a day in mid-January with 

the mercury at zero, as they do in June when it registers 

100 degrees in the shade.” Tanaka (2002) demonstrated 

that in Periplaneta japonica the ability to move at low 

temperature is acquired seasonally. During winter, last instar 

nymphs recover from being buried in ice in 100 

sec, with some of them moving immediately; in summer, 

movement was delayed by 600 sec. 

As in other insects, two main physiological responses 

contribute to winter hardiness in cockroaches: freeze tolerance 

and the prevention of intracellular ice formation 

by supercooling. Regardless of the season, Cel. quinquemaculata 

is freeze tolerant, with a lower lethal temperature 

in winter. Supercooling points fluctuate throughout 

the year, but the insect uses potent ice nucleators to avoid 

extensive supercooling. Its level of protection is just adequate 

for the New Zealand mountains in which it lives, 

where the climate is unpredictable and temperatures as 

low as 4C have been recorded in summer. This cockroach 

may undergo up to 23 freeze-thaw cycles during the 

coldest months and remain frozen for up to 21 hr. The 

added protection of buffered microhabitats is necessary 

for survival in some winters (Sinclair, 1997, 2001; Worland 

et al., 1997). The North American montane species 

Cryptocercus punctulatus lives in a more predictable seasonal 

climate, with the added climatic buffer of a rotting 

log habitat. It is freeze tolerant only in winter; it uses the 

sugar alcohol ribitol as an antifreeze in transitional 

weather, and as part of a quick-freeze system initiated 

by ice-nucleating proteins when the temperature drops 

(Hamilton et al., 1985). There was a 76% survival rate 

among individuals held up to 205 days at 10C, and 

winter-conditioned cockroaches that are frozen become 

active as soon as they are warmed to room temperature. 

Cold hardiness has also been studied in P. japonica (Tanaka 

and Tanaka, 1997), Parc. pennsylvanica (Duman, 

1979), Perisphaeria spp., and Derocalymma spp. (Sinclair 

and Chown, 2005). 

Seasonality and Life Histories 

In trapping studies of cockroaches it is usually unknown 

if the failure to collect a particular species is due to the absence 

of the taxon in the habitat, the absence of the targeted 

life stage, or the current inactivity of the targeted 

life stage. Light traps or windowpane traps, for example, 

will collect only adult stages of volant cockroaches during 

the active part of their diurnal and seasonal cycle; taxa 

absent from these traps may be plentiful as oothecae 

and juveniles in the leaf litter. It is therefore important 

to discuss seasonal activity within the framework of a 

particular taxon’s life history strategy (Daan and Tinbergen, 

1997). There are complex, multivariate interactions 

among generation time, the size at maturity, age, lifespan, 

and growing season length (Fischer and Fiedler, 2002; 

Clark, 2003). Diapause and quiescence further interact 

with developmental rates to synchronize lifecycles, determine 

patterns of voltinism, and regulate seasonal phenology. 

In seasonal environments life histories typically balance 

time constraints, with the synchronization of adult 

emergence most crucial when nymphal development is 

extended and adults are relatively short lived (Brown, 

1983). Hatching must be timed so that seasonal mortality 

risks to juveniles are minimized. In P. japonica, for example, 

first-instar nymphs do not recover following tissue 

freezing, although mid- to large-size nymphs survive 

(Tanaka and Tanaka, 1997). The most thoroughly studied 

lifecycles among temperate cockroaches are those of the 

genus Ectobius. All three species in Great Britain spend 

winter in egg stage diapause, and hatch over a limited period 

in June after 6–7 mon of dormancy (Fig. 3.6). Ectobius 

panzeri is univoltine, while E. lapponicus and E. pallidus 

have semi-voltine lifecycles. Nymphs and eggs of the 

HABITATS 43

latter two species diapause in winter in alternate years, 

but there is complex intrapopulation variability in both 

species. At the onset of winter the nymphs move to grass 

tussocks and assume a characteristic posture: the body is 

flexed ventrally and the legs and antennae are held close 

to the body. Nymphs may feed during the winter, but no 

molting occurs from the end of September until the end 

of April or beginning of May. Adults are short lived; males 

die shortly after mating in June, but females live until October 

(Brown, 1973a, 1973b, 1980, 1983). It is also notable 

that of the three species of Ectobius in Great Britain, the 

smallest species, E. panzeri (Brown, 1952), is the only one 

with a univoltine cycle. Ectobius duskei, abundant in the 

bunch grasses of Asian steppe zones, is also univoltine 

and endures winters of 30 to 40C in the egg stage 

(Bei-Bienko, 1950, 1969). It is thought that short favorable 

seasons often lead to compressed life histories such 

as these, characterized by brief developmental times, high 

growth rates, and smaller adult sizes (Abrams et al., 

1996). A radically different life history, however, is exhibited 

by temperate cockroaches in the genus Cryptocercus, 

and by members of the blaberid subfamily Panesthiinae. 

Nymphs have extended developmental periods and the 

full length of the growing season is required to complete 

a reproductive episode in both Cryptocercus and Panesthia 

(Rugg and Rose, 1984b). Female C. punctulatus 

paired with males the previous summer begin exhibiting 

ovariole and accessory gland activity in April and oviposit 

in late June and early July. Oothecae hatch in late July and 

early August, with most neonates reaching the third or 

fourth instar prior to the onset of winter (Nalepa, 1988a, 

and pers. obs.). Additional temperate species that have 

been studied include An. tamerlana in the Turkmenistan 

desert (3-yr lifecycle in males, 4–6 yr in females) (Kaplin, 

1995), and P. japonica, with a 2-yr lifecycle. The first winter 

is passed as early instar nymphs, the second one as 

late-instar nymphs (Shindo and Masaki, 1995). 

Recently Tanaka and Zhu have been studying the lifecycles 

of several species of subtropical cockroaches on 

Hachijo Island in Japan. Margattea satsumana is a univoltine 

species that overwinters as a non-diapause 

adult. Nymphs undergo a summer diapause, but develop 

quickly in autumn under short-day photoperiods. The 

authors suggest that the summer diapause of nymphs is 

related to a need for timing reproduction during the following 

spring (Zhu and Tanaka, 2004b). Opisthoplatia 

orientalis and Symploce japanica on this island are both 

semi-voltine. The latter has a complex 2-yr lifecycle with 

three kinds of diapause (Tanaka and Zhu, 2003): a winter 

diapause in mid-size nymphs, a summer diapause in latestage 

nymphs, and a winter diapause in adults. Opisthoplatia 

orientalis is a large (25–40 mm) brachypterous 

species capable of overwintering successfully in any stage 

Fig. 3.6 Lifecycle of three species of Ectobius in Great Britain. 

After Brown (1973b), with permission from V.K. Brown. 

without diapause. The ovoviviparous females spend the 

winter with several different stages of oocytes and embryos 

held internally, but the growth of these is suppressed. 

Most of the eggs and embryos do not survive to 

partition. As a result female ovarian development is reset 

in spring; there is a synchronized deposition of nymphs 

in summer, most of which reach the fifth instar prior to 

winter (Zhu and Tanaka, 2004a). This somewhat odd 

strategy may be related to the fact that these cockroaches 

are at the northern limit of their distribution on Hachijo 

Island, where they are not endemic. 

RANGE OF HABITATS 

Cockroaches are found in a continuum of dark, humid, 

poorly ventilated, and often cramped spaces either continuously 

or when sheltering during their non-active period. 

Although certain species may be associated with a 

particular crevice type like the voids beneath rocks or the 

space beneath loose bark, others are commonly found in 

more than one of these habitat subdivisions. Many species 

exploit the interconnectivity of dark, enclosed spaces 

wherever there is suitable food and moisture, and a distinctive 

classification of cockroaches as either obligate or 

facultative inhabitants of caves, litter, or soils is not always 

a natural one (Peck, 1990). The cave and the forest floor 

differ far more from the open-air habitat than they do 

from each other (Darlington, 1970). In closely grown 

tropical and subtropical forest almost all atmospheric 

movements are inhibited, surface evaporation of the 

leaves maintains a high humidity, and the canopy shields 

the forest floor from the direct rays of the sun. Cockroaches 

that live in the maze of hiding places that exist in 

suspended soils or on the forest floor live in a doubly 

blanketed environment, as moist plant litter further 

dampens the small fluctuations of light, temperature, and 

humidity that prevail throughout the forest (Lawrence, 

1953). Caves, on the other hand, encompass a continuum 

of various sized dark, humid voids. To an arthropod, 

44 COCKROACHES

these could range from a few millimeters in size to the 

largest caverns, and may occur in soil layers, fractured 

rock, lava tubes, and talus slopes (Howarth, 1983). All of 

these spaces, whether created by the insect or naturally 

occurring in soil, leaf litter, guano, debris, rotten wood, or 

rock are similar in that they are dark, often humid, and 

buffered from temperature fluctuations. 

It is obvious that a crevice-seeking/burrowing lifestyle 

is suited to a wide range of habitats, as long as dark, humid 

spaces are present or the substrate allows for their 

creation. Burrowing, the act of manufacturing or enlarging 

a space for shelter, is common among Blattaria, but 

there is a fine line of distinction between a cockroach 

forcing itself into an existing void, such as one under 

loose bark, and actually tunneling into the soft, rotted 

wood beneath. Both photonegativity and positive thigmotaxis 

predispose cockroaches to burrowing behavior. 

Beebe (1925, p. 147) offers a vivid definition of positive 

thigmotaxis: “having the irresistible desire to touch or be 

touched by something, above, below, and—a thigmotac’s 

greatest joy—on all sides at once” (Fig. 3.7). Additional 

traits that favor successful colonization of dark, dank 

habitats include the use of non-visual cues in detecting 

food, mates, and predators, a lack of highly specialized 

feeding habits, and physiological adaptations to food 

scarcity (Darlington, 1970; Culver, 1982; Langecker, 

2000). 

A subterranean niche offers a relatively simple habitat, 

with climatic stability and a degree of protection from 

predators. These benefits are countered by physical and 

physiological challenges that must be met for successful 

occupancy. Costs may be incurred in obtaining or constructing 

burrows and shelters. The insect must cope with 

an environment that is aphotic, low in production, and 

high in humidity, endo- and ectoparasites, and pathogens 

(Nevo, 1999). Suboptimum O 2 

and toxic CO 2 

levels are 

also common in burrows, in caves, in wet, decaying logs, 

at high altitudes, and when insects are encased in snow 

and ice (Mani, 1968; Cohen and Cohen, 1981; Hoback 

and Stanley, 2001). 

For our discussion of cockroach habitats, we recognize 

five broad subdivisions: (1) cockroaches that shelter in 

Fig. 3.7 Section through a crevice showing the characteristic 

rest position of a cockroach. From Cornwell (1968), with permission 

of Rentokil Initial plc. 

loose substrates (plant litter, guano, uncompacted soil, 

dust); (2) crevice fauna (under logs, bark, stones, and 

clumps of earth, in rolled leaves, leaf bases, bark crevices, 

scree); (3) those that excavate burrows in a solid substrate 

(wood, soil); (4) those that make use of existing nests or 

burrows (active or abandoned nests of social insects and 

small vertebrates); and (5) those in large burrows: caves 

and cave-like habitats like sewers and mines. We then address 

cockroaches found in three rather specialized habitats: 

deserts, aquatic environments, and the forest canopy. 

We are aware that there are difficulties in adhering to 

these distinctions, as the subdivisions grade into each 

other and species often span categories. Many cockroaches 

that do not routinely inhabit a burrow, for example, 

may construct underground chambers for rearing the 

young, for hibernation, for aestivation, or for molting. 

Many species travel between shelter and sites of feeding 

and reproductive activity; others (especially those in categories 

3 and 4) live their entire life in shelter, except for 

brief dispersal periods. Some cockroaches never leave 

sheltered spaces (some cases of category 5). Those in category 

3 actively create their living space, while those in the 

other four categories generally choose advantageous locations 

among existing alternatives. In each category, 

variation exists that is rooted in resource quality, quantity, 

and location. 

In Loose Substrate 

Cockroaches in this category either tunnel in uncompacted 

substrate (loose soil, dust, sand, guano), which 

may collapse around them as they travel through it, or 

they utilize small, preexisting spaces (dirt clods, leaf litter, 

and other plant debris), which their activities may enlarge. 

Many remain beneath the surface only during inactive 

periods, although those in guano and leaf litter, 

particularly juveniles, may conduct all activities there. 

Certainly the largest class in this category are cockroaches 

that tunnel in plant litter found on forest floors, in the 

suspended soils of the canopy (e.g., in epiphytes, treeholes, 

tree forks), and in piles concentrated by the actions 

of wind, water, or humans. Some species tunnel only as a 

defense from predators, or in response to local or seasonal 

conditions. Substrate categories are often fluid. Those 

that burrow in guano may also burrow in dirt, and those 

that tunnel in leaf litter may continue into the superficial 

layers of soil. Adults of Therea petiveriana in the dry, 

scrub jungles of India burrow in soil, leaf litter, and debris 

(including garbage dumps) during their non-active 

period (Livingstone and Ramani, 1978). The nymphs are 

subterranean and prefer the zone between the litter and 

the underlying humus, but may descend 30 cm during 

dry periods (Bhoopathy, 1997). Other versatile burrowers 

HABITATS 45

include Blaberus spp., which readily bury themselves 

in dirt or loose guano (Blatchley, 1920; Crawford and 

Cloudsley-Thompson, 1971), and Pycnoscelus spp., found 

in a wide variety of habitats as long as they can locate appropriate 

substrate for burrowing (Roth, 1998b; Boyer 

and Rivault, 2003). All stages of Pyc. surinamensis tunnel 

in loose soil, and are also reported from rodent burrows 

(Atkinson et al., 1991). The sand-swimming desert cockroaches 

fall into this category, as well as species such as Ergaula 

capensis, where females and nymphs burrow into 

well-rotted coconut stumps (Princis and Kevan, 1955), as 

well as the dry dust at the bottom of tree cavities (Grandcolas, 

1997b). Blattella asahinai is known to burrow into 

leaf litter and loose soil; they are sometimes pulled up 

along with turnips in home gardens (Koehler and Patterson, 

1987). Individuals of Heterogamodes sp. are known 

to bury themselves in sand or earth (Kevan, 1962). Several 

Australian species (Calolampra spp., Molytria vegranda) 

seem to spend the daylight hours underground, 

emerging to feed after dark (Rentz, 1996; D. Rentz, in 

Roth, 1999b). When collected during their active period 

or in light traps they usually sport sand grains on their 

bodies. In caves, Eu. posticus nymphs burrow in the surface 

of loose guano. They may be completely concealed, 

or may rest with their heads on the surface with their antennae 

extended up into the air. If the guano is compacted, 

the cockroaches remain on its surface and are attracted 

to irregularities such as the edge of a wall, a rock, 

or a footprint (Darlington, 1970). The recently described 

species Simandoa conserfariam congregates in groups of 

20 to 50 individuals of all ages deep within the guano of 

fruit bats; none have been observed on the surface (Roth 

and Naskrecki, 2003). 

Crevice Fauna 

The cockroaches considered crevice fauna are those that 

insert themselves into preexisting small voids in generally 

unyielding substrates. These include species found under 

bark, in bark fissures, in the bases of palm fronds and 

grass tussocks, in hanging dead leaves, empty cocoons, 

and hollow twigs, under logs and rocks, in piles of stones, 

rock crevices, and the excavated galleries of other insects. 

An example of the latter is the Malaysian cockroach Margattea 

kovaci, which lives in bamboo internodes accessed 

via holes excavated by boring Coleoptera and Lepidoptera 

(D. Kovach, pers. comm. to LMR). Burrowing 

and crevice-dwelling cockroaches can be categorically 

difficult to separate, particularly species that shelter under 

rotting logs, in rolled leaves, or in the litter wedged 

into the base of bunch grasses, spinifex, or the leaf axils of 

many plants. The spaces under rocks and stones are a particularly 

important microhabitat for cockroaches in unforested 

areas. Species of the genera Deropeltis and Pseudoderopeltis, 

for example, are abundant under the boulders 

“bestrewing the Masai steppe country” (Shelford, 

1910b). Rock-soil interfaces may also act as corridors between 

habitats, serving as oases for cockroaches moving 

between caves, or between patches of forest (Lawrence, 

1953). Some cockroach species are morphologically specialized 

to inhabit the wafer-thin crevices under bark or 

rocks (Fig. 1.10). The incredibly flattened bodies of tropical 

Australian Mediastinia spp. allow them to slip into the 

unfolding leaves of gingers, lilies, and similar plants during 

the day. At night they move to new quarters as the 

leaves of their previous shelters unfold (D. Rentz, pers. 

comm. to CAN). 

In Solid Substrate 

Cockroaches that excavate permanent burrows in solid 

materials such as wood or compacted soil are more specialized 

than those that use loose substrate or crevices. 

They typically exhibit a suite of ecological and behavioral 

features associated with their fossorial existence, and external 

morphology tends to converge. There are two major 

groups that fall into this category, the Cryptocercidae 

and the Panesthiinae, the latter of which includes the soilburrowing 

cockroaches. There are other species whose 

morphology suggests they are strong burrowers, but little 

has been published on their field biology. The hissing 

cockroaches, including Gromphadorhina portentosa, have 

the general demeanor of burrowers. In a recently published 

book on the natural history of Madagascar, however, 

the only mention of these cockroaches is as prey for 

some vertebrates and as hosts for mites (Goodman and 

Benstead, 2003). 

Burrows in solid substrates offer mechanical protection, 

as well as shelter from some classes of parasites and 

predators. The fact that dispersal in both the Cryptocercidae 

and Geoscapheini occurs following rainfall when 

excavation is likely to be more efficient (Rugg and Rose, 

1991; Nalepa, 2005) suggests that burrow creation is energetically 

costly. Pathogens may accumulate in tunnels, 

and occupants may not be able to escape if a predator enters 

the excavated space. It is unknown if burrowing cockroaches 

have strategies for dealing with flooded burrows, 

or with the often peculiar O 2 

to CO 2 

ratios that may occur. 

In Wood 

Dead wood is a tremendously diverse resource that varies 

with plant taxon, size (branch to bole), location (forest 

floor to suspended in canopy), degree and type of rot, orientation 

(standing versus prone), presence of other invertebrates, 

and other factors. Cockroach species from 

46 COCKROACHES

Table 3.2. Examples of cockroaches other than Cryptocercidae and Panesthiinae that have been 

collected from rotted wood. 

Cockroach species Habitat Reference 

Anamesia douglasi Under bark, in rotting Roach and Rentz (1998) 

wood, in fallen timber 

Austropolyphaga queenslandicus Colonies in preformed Roach and Rentz (1998) 

chambers in dead logs 

and stumps 

Lauraesilpha mearetoi In soft wood of small, Grandcolas (1997c) 

dead branches 

Lamproblatta albipalpus Rotten logs and banana Hebard (1920a) 

trucks, leaf litter 

Gautier and Deleporte 

(1986) 

Laxta granicollis Under bark, in rotting Roach and Rentz (1998) 

Lax. tillyardi 

wood 

Litopeltis bispinosa Rotting banana and Roth and Willis (1960) 

coconut palms 

Methana parva Under bark, in rotting Roach and Rentz (1998) 

wood 

Panchlora nivea Rotting banana and Roth and Willis (1960) 

coconut palms, rotten Séin (1923) 

wood 

Panchlora spp. Rotting logs, stumps, Wolcott (1950) 

woody vegetation Fisk (1983) 

Paramuzoa alsopi Juveniles in dead wood Grandcolas (1993b) 

Parasphaeria boleiriana In soft, rotten wood Pellens et al. (2002) 

Polyphagoides cantrelli In rotting wood Roach and Rentz (1998) 

Robshelfordia hartmani In rotting wood, females Roach and Rentz (1998) 

also collected in caves 

Sundablatta pulcherrima 1 Abundant in decayed Shelford (1906c) 

wood 

Ylangella truncata Adults under bark; C. Rivault (pers. comm. to 

juveniles deep in rotten CAN) 

tree trunks 

1 

Described as Pseudophyllodromia pulcherrima by Shelford (1906c); LMR’s notes on the Shelford manuscript indicate 

it is in the genus Sundablatta. 

most families have been collected from rotting logs (Table 

3.2), but in the majority of cases it is unknown whether 

these feed on wood and associated microbes, if they depart 

to forage elsewhere, or both. This category is more 

fluid than generally recognized, and divisions in the dietary 

continuum of rotted leaf litter, soft rotted wood, and 

wood-feeding are not always easy to make. This is particularly 

true of the many cockroaches that bore into the 

well-rotted trunks and stalks of coconut and banana 

palms, which have been described as “gigantic vegetables 

with a stalk only a little tougher than celery”(Perry, 1986). 

Some cockroaches (e.g., Blaberus) are found in rotting 

logs as well as a variety of other habitats, others are not 

recorded anywhere else. Tryonicus monteithi, Try. mackerrasae, 

and Try. parvus are found in rotting wood and under 

stones and pieces of wood in Australian rainforest, 

but never under bark or above ground (Roach and Rentz, 

1998). Anamesia douglasi is found under bark and in rotting 

wood, but has also been observed on sand ridges 

(Roach and Rentz, 1998), perhaps sunning themselves 

like some other Polyzosteriinae. Groups of similar-sized 

juveniles of Ylangella truncata, probably hatched from a 

single ootheca, live in galleries deep in the interior of large 

rotting tree trunks. Adults are excellent fliers and are 

found most often just under the bark of these logs. Attempts 

to rear nymphs in the laboratory on pieces of rotted 

wood and a variety of other foodstuffs, however, were 

not successful (C. Rivault, pers. comm. to CAN).A species 

of large, reddish, heavy-bodied hissing cockroach has 

been observed in groups of 40 or 50 inside of rotten 

HABITATS 47

stumps and logs in riverine areas of southeastern Madagascar. 

Groups included both adults and nymphs (G. 

Alpert, pers. comm. to LMR). The least known cockroaches 

in this category are those with the elongated, 

cylindrical body form of many boring beetles. These include 

Compsagis lesnei (Chopard, 1952), found inside of 

tree branches (Fig. 1.14), and several species of Colapteroblatta 

( Poroblatta) (Roth, 1998a), which Gurney 

(1937) described as boring into stumps and logs in a 

manner similar to Cryptocercus. There are probably many 

more wood-boring cockroaches yet to be discovered, particularly 

in the substantial amount of dead and dying 

wood suspended in tropical canopies. 

Both sexes of all species in the monogeneric family 

Cryptocercidae are wingless and spend their lives in decaying 

wood on the floor of montane forests in the 

Palearctic and Nearctic (Nalepa and Bandi, 1999). As 

might be expected for insects feeding on dead wood, their 

distribution and abundance varies in relation to patterns 

of tree mortality if other habitat requirements are met 

(Nalepa et al., 2002). Presently C. punctulatus in eastern 

North America is numerous at high elevations in logs of 

Fraser fir (Abies fraseri) killed by balsam wooly adelgid 

(Adelges piceae). Formerly they were easily found in chestnut 

logs (Castanea dentata) abundant on forest floors because 

of chestnut blight (Hebard, 1945). Occasionally, all 

families in a log are of the same developmental stage, suggesting 

that a particular log became suitable for colonizing 

at a particular point in time. A log may harbor only 

male-female pairs, for example, or only families with second-year 

nymphs (CAN, pers. obs.). Both Palearctic and 

Nearctic species of Cryptocercus occur in a wide variety of 

angiosperms and conifers, with the log host range determined 

by the plant composition of the inhabited forest. 

Well-rotted logs as well as those that are relatively sound 

serve as hosts (Cleveland et al., 1934; Nalepa and Bandi, 

1999; Nalepa, 2003). The cockroaches are only rarely collected 

from wood undergoing the white rot type of decay 

(Mamaev, 1973; Nalepa, 2003); the conditions associated 

with white rot generally do not favor many groups of animals 

(Wallwork, 1976). Inhabited logs can be quite variable 

in size. Logs harboring C. primarius ranged from 10 

cm to more than 1 m in diameter (Nalepa et al., 2001b). 

Cryptocercus clevelandi is most often collected in logs of 

Douglas fir, the large size of which buffers the insects 

from the warm, dry summers characteristic of southwest 

Oregon (Nalepa et al., 1997). Large logs provide insulation 

from winter cold, but C. punctulatus is also physiologically 

equipped to withstand freezing weather (Hamilton 

et al., 1985). 

Wood-feeding cockroaches in the blaberid subfamily 

Panesthiinae are distributed principally in the Indo- 

Malayan and Australian regions, with a few species extending 

into the Palearctic. Six genera live in and feed on 

rotting wood, and exhibit little variation in morphology 

and habits. Body size, however, can be quite variable; 

Panesthia spp. range from 15 to more than 50 mm in 

length (Roth, 1977, 1979b, 1979c, 1982b). The best studied 

is Panesthia cribrata in Australia, found inside of decaying 

logs but also under sound logs, where they feed on 

the wood surface in contact with the ground. They are 

sometimes found in the bases of dead standing trees 

(Rugg and Rose, 1984a; Rugg, 1987). Host choice in these 

blaberids is similar to that of Cryptocercus. Panesthia 

cribrata in Australia (Rugg, 1987), as well as species of 

Panesthia and Salganea in Japan (K. Maekawa, pers. 

comm. to CAN) utilize softwood as well as hardwood 

logs. They generally use what is available, and when populations 

are high, they are found in a greater variety of log 

types (D. Rugg, pers. comm. to CAN). 

All Cryptocercidae and wood-feeding Panesthiinae 

studied to date are slow-growing, long-lived cockroaches. 

Development takes about 4 yr in Cryptocercus kyebangensis 

(Park et al., 2002), C. clevelandi takes 5–7 yr, and C. 

punctulatus requires 4–5 yr. In the latter two species, 

adults pair up during the year they mature, but do not reproduce 

until the following summer. Thus the time from 

hatch to hatch in C. clevelandi is 6–8 yr, and in C. punctulatus 

5–6 yr. Post reproduction, adults of these two 

species live for 3 or so yr in the field, females longer than 

males (Nalepa et al., 1997). Rugg and Rose (1990) calculated 

that the nymphal period of Pane. cribrata was at 

least 4–6 yr, and that the field longevity of adults exceeds 

4 yr. Panesthia cribrata, as well as Pane. australis, Pane. 

matthewsi, Pane. sloanei, and Pane. angustipennis spadica 

live in aggregations, most often comprised of a number 

of adult females, an adult male, and nymphs of various 

sizes. Nymphs are also commonly found in groups without 

adults (Rugg and Rose, 1984a). Panesthia cribrata reproduces 

once per year, but probably gives birth each year 

(Rugg and Rose, 1989). All species of Cryptocercus studied 

to date live in monogamous family groups, and produce 

just one set of offspring, with an extensive period of 

parental care following (Seelinger and Seelinger, 1983; 

Nalepa, 1984; Nalepa et al., 2001b; Park et al., 2002). The 

panesthiine genus Salganea is also subsocial (Matsumoto, 

1987; Maekawa et al., 1999b), but at least one species (Sal. 

matsumotoi) is iteroparous (Maekawa et al., 2005). 

In Soil 

Those cockroaches known to tunnel in uncompacted 

media such as leaf litter or loose soil occasionally make 

forays into more solid substrates. Periplaneta americana 

nymphs and adults have been observed digging resting 

48 COCKROACHES

sites in the clay wall of a terrarium (Deleporte, 1985), and 

Pyc. surinamensis can excavate tunnels that extend up to 

13 cm beneath the soil surface. These tubes may end in a 

small chamber where juveniles molt and females bear 

young (Roesner, 1940). At least two unstudied blaberids 

in the subfamily Perisphaeriinae appear to live in permanent 

soil burrows. Female Cyrtotria ( Stenopilema) are 

found in a burrows surrounded by juveniles (Shelford, 

1912b). Similarly, a female Pilema thoracica accompanied 

by several nymphs was taken from the bottom of a neat 

round hole about 15 cm in depth; there were about a 

dozen such holes in half an acre and all contained families 

of this species (Shelford, 1908). Cockroaches of a 

Gromphadorhina sp. have been observed in a ground burrow 

in grassland of the Isalo National Park in Madagascar. 

The heads and antennae of both adults and nymphs 

were projecting from the entrance, which was about 5 cm 

in diameter (G. Alpert, pers. comm. to LMR). 

All other cockroaches that form permanent burrows 

in compacted soil belong to four Australian genera of 

the subfamily Panesthiinae: Macropanesthia, Geoscapheus, 

Neogeoscapheus, and Parapanesthia (Roth, 1991a). They 

are distributed mainly east of the Great Dividing Range 

with a concentration in southeast Queensland (Roach 

and Rentz, 1998). The giant burrowing cockroach M. rhinoceros 

is the best studied (Rugg and Rose, 1991; Matsumoto, 

1992), but the biology of the other species is similar 

(D. Rugg, pers. comm. to CAN). All feed on dry plant 

litter that they drag down into their burrows. Burrow entrances 

have the characteristic shape of a flattened semicircle, 

but may be slightly collapsed or covered by debris 

during the dry season. Tunnels initially snake along just 

beneath the soil, then spiral as they descend and widen 

out; they tend to get narrow again at the bottom. Litter 

provisions are typically stored in the wider part, and the 

cockroaches retreat to the narrow blind terminus when 

alarmed. They are not known to clean galleries; consequently, 

debris and excrement accumulate (Rugg and 

Rose, 1991; D. Rugg, pers. comm. to CAN). Species distribution 

is better correlated with soil type than with vegetation 

type. Burrows of M. rhinoceros may be found in Eucalyptus 

woodland, rainforest, or dry Acacia scrub, as long 

as the soil is sandy. Other species are associated with gray 

sandy loams, red loam, or hard red soil (Roach and Rentz, 

1998). The depth of Macropanesthia saxicola burrows is 

limited by the hard heavy loam of their habitat, and those 

of M. mackerrasae tend to be shallow and non-spiraling 

because they run up against large slabs of rock. The deepest 

burrows are those of females with nymphs, the shallowest 

are those of single nymphs (Rugg and Rose, 1991; 

Roach and Rentz, 1998). Female M. rhinoceros reproduce 

once per year, and nymphs remain in the tunnel with 

females for 5 or 6 mon before they disperse, initiate 

their own burrows, and begin foraging. These mid-size 

nymphs then enlarge their burrows until adulthood. Development 

requires a minimum of 2 or 3 yr in the field, 

but growth rates are highly variable. Adults live an additional 

6 yr (Rugg and Rose, 1991; Matsumoto, 1992). 

Males are occasionally found in the family during early 

stages of the nesting cycle. Both sexes emerge from burrows 

after a rainfall, with females foraging and males 

looking for females. Surface activity in M. rhinoceros occurs 

from just before midnight to a couple of hours after 

sunrise; peak of activity is 2 or 3 hr before sunrise. Small 

nymphs are never observed above ground (Rugg and 

Rose, 1991). 

Recent evidence indicates that among the Panesthiinae, 

the ecological and evolutionary boundaries between 

the soil-burrowing–litter-feeding habit, and one of living 

in and feeding on wood, are more fluid than expected. In 

1984, Rugg and Rose (1984c) proposed that the soil-burrowing 

cockroaches be elevated to the rank of subfamily 

(Geoscapheinae) on the basis of their unique reproductive 

biology. Recently, however, a molecular analysis of 

three genes from representatives of nine of the 10 Panesthiinae 

and Geoscapheini genera by Maekawa et al. 

(2003) indicates that these taxa form a well-supported 

monophyletic group, with the former paraphyletic with 

respect to the latter (Fig. 2.13). These authors propose 

that the ancestors of soil-burrowing cockroaches were 

wood feeders driven underground during the Miocene 

and Pliocene, when dry surface conditions forced them to 

seek humid environments and alternative sources of 

food. This suggestion is eminently reasonable, as there are 

isolated cases of otherwise wood-feeding cockroach taxa 

collected from soil burrows or observed feeding on leaf 

litter. Ancaudellia rennellensis in the Solomon Islands lives 

in underground burrows (Roth, 1982b), even though the 

remaining species in the genus are wood feeders. There is 

also a record of a male, a female, and 19 nymphs of 

Panesthia missimensis in Papua New Guinea collected 

0.75 m deep in clay, although others in the species were 

collected in rotten logs (Roth, 1982b). Although the preferred 

habitat of the endangered Panesthia lata is decaying 

logs, Harley Rose (University of Sydney) has also 

found them under rocks, sustaining themselves on Poa 

grass and Cyperus leaves (Adams, 2004). Even individuals 

or small groups of C. punctulatus are sometimes found in 

a small pocket of soil under a log, directly beneath a 

gallery opening (Nalepa, 2005), particularly when logs 

become dry. These examples are evidence that the morphological 

adaptations for burrowing in wood also allow 

for tunneling in soil, and that the digestive physiology of 

wood-feeding Panesthiinae may be flexible enough to al- 

HABITATS 49

low them to expand their dietary repertoire to other 

forms of plant litter when required. 

In Existing Burrows and Nests 

Some cockroaches specialize in using the niche construction, 

food stores, and debris of other species. Whether 

these cockroaches elude their hosts or are tolerated by 

them is unknown. Of particular interest are the cockroaches 

that live with insectivorous vertebrates such as 

rodents and some birds. How do the cockroaches avoid 

becoming prey? 

Insect Nests 

A number of cockroaches live in the nests of social insects, 

although these relationships are rather obscure. 

Some cockroach species collected in ant and termite 

colonies have been taken only in this habitat (Roth and 

Willis, 1960), and are presumably dependent on their 

hosts. In others, the relationship is more casual, with the 

cockroaches opportunistically capitalizing on the equable 

nest climate and kitchen middens of their benefactors. 

Several species of the genus Alloblatta, for example, scavenge 

the refuse piles of ants (Grandcolas, 1995b). Similar 

garbage-picking associations are found in Pyc. surinamensis 

with the ant Campanotus brutus (Deleporte et al., 

2002), and in nymphs of Gyna with Dorylus driver ants 

(Grandcolas, 1997a). Occasional collections from insect 

nests include the Australian polyphagid Tivia australica, 

recorded from both litter and ant nests, and the blattellid 

Paratemnopteryx australis, collected from under bark, in 

litter, and from termite (Nasutitermes triodiae) nests 

(Roach and Rentz, 1998). In the United States, Arenivaga 

bolliana and A. tonkawa have been taken from both nests 

of Atta texana and burrows of small vertebrates (Roth 

and Willis, 1960; Waller and Moser, 1990). In Africa, Er. 

capensis has been collected in open bush, in human habitations, 

and in termite mounds, and is just one of several 

taxa, including Periplaneta, that exploit both human and 

insect societies (Roth and Willis, 1960). 

The records we have of more integrated myrmecophiles 

include the New World genera Myrmecoblatta 

and Attaphila. The polyphagid Myrmecoblatta wheeleri is 

associated with nests of Solenopsis geminata in Guatemala 

(Hebard, 1917), and with the carpenter ants Camponotus 

abdominalis in Costa Rica and C. abdominalis floridanus 

in Florida. Deyrup and Fisk (1984) observed at least 20 

Myr. wheeleri of all sizes when a dead slash pine log was 

turned over in scrubby flatwoods habitat in Florida. All 

Attaphila spp. (Blattellidae) are associated with leaf-cutting 

ants in the genera Atta and Acromyrmex (Kistner, 

1982). The best known is Attaphila fungicola (Fig. 1.16B), 

a species that lives in cavities and tunnels within the fungus 

gardens of Atta texana. Both male and female cockroaches 

have been collected from A. texana nests in Texas 

(Wheeler, 1900), but only females have been collected in 

Louisiana (Moser, 1964). Within the nest, Att. fungicola 

ride on the backs or the enormous heads of soldiers, 

which “do not appear to be the least annoyed” (Wheeler, 

1900). The cockroach mounts a passing host by grabbing 

the venter or gaster, then climbing onto the mesonotum; 

they ride facing perpendicular to the long axis of the ant’s 

body. The weight of the cockroach may cause the ant to 

topple over (J.A. Danoff-Burg, pers. comm. to WJB). Perhaps 

for this reason, Attaphila chooses for steeds the soldiers, 

the largest ants in the colony. The cockroaches run 

along with ants as well as riding on them, and can detect 

and orient to ant trail pheromone (Moser, 1964), presumably 

via a unique structure on the maxillary palps 

(Brossut, 1976). Wheeler (1900) originally thought that 

the cockroaches fed on the ant-cultivated fungus within 

the nest, but later (1910) decided that they obtain nourishment 

by mounting and licking the backs of soldiers. It 

is, of course, possible that they do both. 

Recently, another myrmecophile has been described 

from jungle canopy in Malaysia, leading us to believe that 

there are many more such associations to be discovered 

in tropical forests. The ovoviviparous blattellid Pseudoanaplectinia 

yumotoi was found with Crematogaster deformis 

in epiphytes (Platycerium coronarium) exposed to 

full sunlight 53 m above the ground. The leaves of these 

stag’s horn ferns form a bowl that encloses the rhizome, 

roots, and layers of old leaves within which the ants and 

cockroaches live. More than 2800 Ps. yumotoi were collected 

from one nest of about 13,000 ants. The ants protect 

the cockroaches from the attacks of other ant species. 

Living cockroaches are not attacked by their hosts, but 

ants do eat the dead ones (Roth, 1995c; T. Yumoto, pers. 

comm. to LMR). At least two cockroach species exploit 

the mutualism between ants and acacias. Blattella lobiventris 

has been found in swollen acacia thorns together 

with Crematogaster mimosae (Hocking, 1970). Female 

Nyctibora acaciana glue their oothecae near Pseudomyrmex 

ant nests on acacias, apparently for the protection 

provided by the ants against parasitic wasps (Deans 

and Roth, 2003). 

Several species of cockroaches in the genus Nocticola 

have been found within the nests of termites but nothing 

is known about their biology or their relationship with 

their hosts (Roth and Willis, 1960; Roth, 2003b). The majority 

of these are associated with fungus-growing termites 

(Macrotermes and Odontotermes), which in the 

Old World are the ecological equivalents of Atta. This 

strengthens the suggestion that fungus cultivated by social 

insects may be an important dietary component of 

cockroach inquilines. Many cockroach species can be 

50 COCKROACHES

found in deserted termite mounds (Roth and Willis, 

1960). 

Few cockroaches have been found in nests of Hymenoptera 

other than ants. The minute (3 mm) species 

Sphecophila polybiarum inhabits the nests of the vespid 

wasp Polybia pygmaea in French Guiana (Shelford, 

1906b). Apparently the cockroaches feed on small fragments 

of prey that drop to the bottom of the nest when 

wasps feed larvae. Parcoblatta sp. (probably Parc. virginica) 

are commonly found (68% of nests) scavenging 

bits of dropped prey and other colony debris in subterranean 

yellowjacket (Vespula squamosa) nests at the end 

of the colony cycle (MacDonald and Matthews, 1983). 

Similarly, Oulopteryx meliponarum presumably ingest 

excreta and other debris scattered by the small stingless 

bee Melipona. Additional associations are discussed in 

Roth and Willis (1960). 

Cockroaches living in the nests of social insects profit 

from protective services, a favorable microclimate, and a 

stable food supply in the form of host-stored reserves and 

waste material. The only benefit to the hosts suggested in 

the literature is the opportunity to scavenge the corpses 

of their guests. Ants generally ignore live Attaphila in the 

nest (Wheeler, 1900), but the mechanism by which the 

cockroaches are integrated into colony life has not been 

studied. Like other inquilines, however, the cuticular hydrocarbons 

of these cockroaches may mimic those of 

their hosts. Gas chromatography indicates that the surface 

wax of Ps. yumotoi is similar to that of their ant hosts 

(T. Yumoto, pers. comm. to LMR), but it is yet to be determined 

whether these are acquired from the ants by 

contact or ingestion, or if they are synthesized de novo. 

Cuticular hydrocarbons are easily transferred by contact 

between two different species of cockroaches. After 14 

days in the same container N. cinerea and R. maderae 

merge into one heterospecific group with cuticular 

profiles that show characteristics of both species (Everaerts 

et al., 1997). Ants can acquire the hydrocarbons of a 

non-myrmecophile cockroach (Supella longipalpa) via 

physical contact; these ants are subsequently recognized 

as foreign by their nestmates and attacked (Liang et al., 

2001). Individuals of Attaphila fungicola spend so much 

time licking soldiers (Wheeler, 1910) that these myrmecophiles 

may be internally acquiring and then reusing 

epicuticular components of their host. 

Vertebrate Burrows 

Most records of Blattaria in vertebrate burrows come 

from deserts (discussed below), as the high moisture content 

of these habitats is advantageous in arid environments. 

Cockroach food sources in these subterranean 

spaces include organic debris, and the feces, cached food, 

and dead bodies of inhabitants (Hubbell and Goff, 1939). 

Roth and Willis (1960) indicate that cockroach species 

found in animal burrows are usually different than those 

that inhabit caves. Richards (1971), however, suggests 

that burrows may be important as intermediate stops 

when cockroaches move between caves, and gives as example 

the often cavernicolous species Paratemnopteryx 

rufa found in wombat burrows. 

Bird Nests 

Cockroaches are only rarely associated with the shallow 

cup-type nest typical of many birds. The one exception 

known to us is Euthlastoblatta facies, which lives in large 

numbers among twigs in the nests of the gray kingbird in 

Puerto Rico (Wolcott, 1950). Most records are from the 

nests of birds that breed gregariously and construct pendulous, 

teardrop-shaped nests up to 1 m long (Icteridae) 

or large, hanging apartment houses of dry grass (Ploceinae). 

Roth (1973a) collected about 10 species of cockroaches 

in the pendulous nests of an icterid (probably the 

oriole, Cassicus persicus) in Brazil. Schultesia lampyridiformis 

was found in 2 of 7 nests of Cassicus about 18 m 

above ground in the Amazon. Van Baaren et al. (2002) 

found 5 species in icterid bird nests in French Guiana: 

Schultesia nitor, Phoetalia pallida, Pelmatosilpha guianae, 

Chorisoneura sp., and Epilampra grisea. Immature cockroaches 

were common in the nests of Ploceinae in Madagascar 

and the Ivory Coast; all nests of Foundia spp. examined 

in Madagascar harbored cockroaches restricted 

to this habitat (Paulian, 1948). Griffiniella heterogamia 

lives in nests of a social weaver bird in southwest Africa 

(Rehn, 1965). Most icterid nests inhabited by the cockroaches 

were abandoned, and a few carried the remains 

of dead young birds. The cockroaches are probably scavengers 

and may also occupy the nests while birds are present 

(Roth, 1973a). 

In Caves and Cave-Like Habitats 

Cockroaches are well represented in caves throughout the 

tropics and subtropics, from 30N to 40S of the equator; 

they are uncommon in temperate caves (Izquierdo and 

Oromi, 1992; Holsinger, 2000). Except for rare collections 

of Arenivaga grata and Parcoblatta sp., no cave cockroaches 

occur in the continental United States (Roth and 

Willis, 1960; Peck, 1998). The biology of cave-dwelling 

cockroaches has been studied most extensively in Trinidad 

and Australia. In Guanapo Cave in Trinidad, Eublaberus 

distanti is dominant, with Blab. colloseus and 

Xestoblatta immaculata also found (Darlington, 1995– 

1996). These three species, as well as Eub. posticus, are also 

found in the Tamana Caves (Darlington, 1995a). Six 

cockroach species are reported from caves of the Nullarbor 

Plain of southern Australia: Polyzosteria mitchelli, 

HABITATS 51

Polyz. pubescens, Zonioploca medilinea (Blattidae), Neotemnopteryx 

fulva, Trogloblattella nullarborensis, and Para. 

rufa (Blattellidae). Three are considered accidentals, 

two are facultative, and one is an obligate cavernicole 

(Richards, 1971). Cockroaches in the family Nocticolidae 

are consistent inhabitants of caves throughout the Old 

World tropics (Stone, 1988; Deharveng and Bedos, 2000). 

Of the approximately 20 species in the widely distributed 

genus Nocticola, most are cavericolous, a few are epigean 

or termitophilous, and a few can be found both inside and 

outside of caves (e.g., Alluaudellina himalayensis) (Roth, 

1988; Roth and McGavin, 1994). Juberthie (2000a) estimated 

that worldwide, 31 cockroaches species are known 

to be obligate cavernicoles, but additional species continue 

to be described (e.g., Vidlička et al., 2003). Table 3.3 

gives examples of cave cockroaches; others are discussed 

in Asahina (1974), Izquierdo et al. (1990), Martin and 

Oromi (1987), Martin and Izquierdo (1987), Roth and 

Willis (1960), Roth (1980, 1988), Roth and McGavin 

(1994), and Roth and Naskrecki (2003). 

It is often difficult to label a given species as a cave cockroach 

for two reasons. First, many of the described species 

are based on few collection records. Second, the term cave 

usually refers to an underground space large enough to 

accommodate a human, but grand expanses such as these 

are just a small part of the subterranean environment 

(Ruzicka, 1999). The limits of the hypogean realm are 

hard to define because cave habitats grade into those of 

the edaphic environment via smaller-scale subterranean 

spaces such as animal burrows, tree holes, hollow logs, the 

area under rocks, and other such dark, humid, organic 

living spaces. Cockroaches found in many of these noncave 

habitats occasionally or consistently exploit caves. 

Those that are considered “accidentals” are only rarely 

collected in caves. Polyz. mitchelli, for example, is a large 

ground-dwelling epigean Australian species that has also 

been taken in caves (Roach and Rentz, 1998). On the 

other hand, those species that typically inhabit cave entrances 

may venture outside the cave if the humidity is 

high enough (e.g., Para. rufa—Richards, 1971). Among 

the cockroaches taken in a range of subterranean-type 

habitats is the Asian species Polyphaga aegyptiaca, found 

in bat caves, under decaying leaves, and in cliffs along 

ravines (Roth and Willis, 1960), and X. immaculata, Eub. 

distanti, Blaberus giganteus, Blab. atropos, and Blab. craniifer. 

The latter are all considered cave cockroaches, but are 

also collected from under decaying litter, in epiphytes, inside 

rotting logs, and in the rot holes and hollows of trees, 

particularly those that house bats (Darlington, 1970; Fisk, 

1977). Perry (1986) described dozens of adult Blab. giganteus 

in a tree hollow “all sitting, as sea gulls on a beach, 

evenly spaced and facing upward.” Blatta orientalis, Blattella 

germanica, and P. americana have all been found in 

caves, as well as in buildings, wells, sewers, steam tunnels, 

and mines 660 m below the surface (Roth and Willis, 

1960; Roth, 1985) (Fig. 3.8). In one sense, however, these 

human-made, non-cave habitats may be considered vertebrate 

burrows. Cockroaches exhibiting morphological 

correlates of cave adaptation such as elongated appendages 

and the loss of pigment, eyes, and wings are 

generally restricted to cave habitats, but even these can be 

found elsewhere. A species of Australian Nocticola with 

reduced eyes and tegmina and no wings lives beneath rotting 

logs (Stone, 1988). The troglomorphic Symploce micropthalmus 

lives in the mesocavernous shallow stratum 

of the Canary Islands, but is also found under stones in 

humid areas (Izquierdo and Medina, 1992). 

Individual caves are commonly divided into zones, 

Table 3.3. Examples of cave-dwelling cockroaches. 

1. Occur in caves sporadically, and sometimes become established there; show no morphological 

characters specifically associated with cave dwelling. 

Examples: Blattidae: Periplaneta americana, Polyzosteria mitchelli; Blaberidae: Pycnoscelus indicus, 

Pyc. surinamensis, Blaberus colosseus 

2. Habitually found in caves, but are able to live in or outside of caves; they show no characters 

adaptive for cave dwelling. 

Examples: Blattidae: Eumethana cavernicola; Blattellidae: Blattella cavernicola; Blaberidae: Blaberus 

craniifer, Eublaberus posticus, Aspiduchus cavernicola 

3. Cannot live outside of caves and show marked morphological specializations for the cave habitat 

(obligate cavernicoles or troglobites). 

Examples: Blattidae: Neostylopyga jambusanensis; Blattellidae: Neotrogloblattella chapmani, 

Loboptera anagae, L. troglobia, Paratemnopteryx howarthi, Para. stonei, Trogloblattella chapmani; 

Nocticolidae: Alluaudellina cavernicola,Typhloblatta caeca, Nocticola simoni, Noc. australiensis, Noc. 

bolivari, Noc. flabella, Spelaeoblatta thamfaranga 

52 COCKROACHES

Fig. 3.8 Periplaneta sp. in a sewer manhole in Houma, Louisiana. 

From Gary (1950). 

with each supporting a different community (Juberthie, 

2000b). The twilight zone near the entrance is closest to 

epigean conditions and has the largest and most diverse 

fauna. Next is a zone of complete darkness with variable 

temperature, and finally in the deep interior a zone of 

complete darkness, stable temperature, and stagnant air, 

where the obligate, troglomorphic fauna appear (Poulson 

and White, 1969). The degree of fidelity to a zone varies. 

While the Australian Para. rufa is found only from the entrance 

to 0.4 km into a cave, Trog. nullarborensis is found 

from the entrance to 4.8 km deep; it roams throughout 

the cave system and is one of the few troglomorphs 

recorded from the twilight zone (Richards, 1971). Eublaberus 

posticus and Eub. distanti may segregate in caves 

according to their particular moisture requirements. The 

former prefers the moist inner sections of caves, while the 

latter is more common in drier guano (Darlington, 1970). 

The habitable areas of caves, and consequently, populations 

of cave organisms, are dynamic—they move, expand, 

and contract, depending on climate and on pulses 

of organic matter (Humphreys, 1993). After an exceptionally 

cool night in Nasty Cave in Australia, for example, 

a common Nocticola cockroach could not be found 

and was thought to have retreated into cracks during the 

unfavorable conditions (Howarth, 1988). Initially a small 

species in the subfamily Anaplectinae was sporadically 

seen in a Trinidadian cave, subsequently formed a thriving 

colony, then was wiped out when the cave flooded. It 

did not reappear (Darlington, 1970). 

Caves with a source of vertebrate guano support very 

different cockroach communities than caves that lack 

such input. Guano caves typically contain very large 

numbers of few cockroach species able to maintain dense 

populations and exploit the abundant, rich, but rather 

monotonous food bonanza (Darlington, 1970). Examples 

include a population of more than 80,000 Gyna sp. 

in a South African cave (Braack, 1989), more than 43,000 

Eub. distanti in just one chamber of a cave in Trinidad 

(Darlington, 1970) (Fig. 3.9), and Pycnoscelus striatus 

found at approximately 2000–3000/m 2 in the Batu Caves 

of Malaysia (McClure, 1965). A similar scenario is that of 

approximately 3000 P. americana /m 2 in a sewer system 

more than 27 m beneath the University of Minnesota 

campus (Roth and Willis, 1957). In guano caves, the distribution 

of cockroaches usually coincides with that of 

bats and their excrement (Braack, 1989). Some species are 

consistently associated with bat guano, wherever it is 

found. One South African Gyna sp. was present in all batinhabited 

caves and cave-like habitats, including the roof 

of a post office (Braack, 1989). 

Highly troglomorphic cockroach species generally 

support themselves on less rich, less abundant food 

sources. Trogloblattella chapmani is typically found remote 

from guano beds in passages floored by damp sticky 

clay or silt (Roth, 1980). Metanocticola christmasensis is 

associated with the often luxuriant tree root systems that 

penetrate caves (Roth, 1999b), but their diet is unknown 

(Roth, 1999b). Troglomorphic cockroaches tend to move 

Fig 3.9 Habitat stratification in Eublaberus distanti in Guanapo 

Cave, Trinidad. (A) Adults on walls of cave; (B) nymphs 

on surface of fruit bat guano. Photos courtesy of J.P.E.C. Darlington. 

HABITATS 53

very slowly (e.g., Nocticola spp.—Stone, 1988; Loboptera 

troglobia—Izquierdo et al., 1990), and produce few eggs. 

The oothecae of Alluaudellina cavernicola contain only 

four or five eggs (Chopard, 1919) and those of Nocticola 

( Paraloboptera) rohini from Sri Lanka contain just four 

(Fernando, 1957). Among the seven species of Loboptera 

studied by Izquierdo et al. (1990) in the Canary Islands, 

reductions in ovariole number paralleled the degree of 

morphological adaptation to the underground environment. 

The least modified species had 16–18 ovarioles, 

while the most troglomorphic had six ovarioles. It is unknown 

whether troglomorphic cockroaches exhibit the 

increased developmental time and lifespan, decrease in 

respiratory metabolism, and loss of water regulatory 

processes found in many other cave-adapted animals 

(Gilbert and Deharveng, 2002). 

Deserts 

While cockroaches are generally associated with humid 

habitats, there are a number of species that have settled 

deserts, scrub, grassland, and other arid environments. 

These habitats vary in temperature, from hot subtropical 

deserts to colder deserts found at high latitudes or high 

elevations. In each, however, low precipitation plays a 

major role in controlling biological productivity. Many 

polyphagids, some blattellids, and a few blattids inhabit 

these xeric landscapes. Polyphagidae are most diverse 

in the deserts of North Africa and South Central Asia 

(Bei-Bienko, 1950), and best studied in Egypt (Ghabbour 

et al., 1977; Ghabbour and Mikhaïl, 1978; Ghabbour 

and Shakir, 1980) and Saudi Arabia (Bei-Bienko, 1950; 

Grandcolas, 1995a). The cockroaches can be very abundant, 

comprising nearly a third of the mesofaunal biomass 

collected in surveys of soil arthropods in the desert 

of northern Egypt (Ayyad and Ghabbour, 1977). In North 

America, polyphagid cockroaches occur in the southwestern 

United States, with one species (Arenivaga floridensis) 

found in Florida. 

Desert-dwelling cockroaches exhibit morphological, 

behavioral, and physiological adaptations for maintaining 

water balance, avoiding or tolerating extreme temperatures, 

and finding food in habitats with sparse primary 

productivity. Behavioral tactics for coping with 

these extreme conditions include diurnal and seasonal 

shifts in spatial location and prudent choice of microhabitat. 

Like many desert arthropods, the sand-swimming 

Polyphagidae take advantage of the more salubrious 

conditions beneath the surface of desert soil. 

Arenivaga investigata migrates vertically in loose sand on 

a diel basis. In spring and summer, activity near the surface 

commences 2 hr after darkness and continues for 

most of the night (Edney et al., 1974). In winter, activity 

corresponds to peaks in nighttime surface temperature 

(Hawke and Farley, 1973). The insects move about just 

beneath the sand (Fig. 2.6), making them less susceptible 

to predators (e.g., scorpions) as they forage for dead 

leaves, roots, and other food. Throughout the year A. investigata 

can find a relative humidity of about 82% by descending 

45 cm in the sand, and can avoid temperatures 

above 40C by moving no lower than 15 cm (Edney et al., 

1974). The cockroaches descend deeper in the sand in 

summer than in winter (Edney et al., 1974) (Fig. 3.10). In 

July, all developmental stages except adult males range 

2.5–30 cm below the surface, with a mode at 12.5 cm. In 

November the insects are found no deeper than 15 cm, 

with most occurring at 5 cm or less. It is possible that the 

maximum depth to which these cockroaches burrow may 

be limited by hypoxia (Cohen and Cohen, 1981). 

Although deserts can be very hot, very dry, and sometimes 

very cold, they have numerous microhabitats where 

the climate is much less extreme. In addition to the depths 

of loose sand, these include the burrows of small vertebrates, 

under boulders, in caves, and amid decaying organic 

material in dry stream beds, at the base of tussocks, 

in rock crevices, and under shrubs or trees (Roth and 

Willis, 1960). Some cockroach species are consistently 

associated with one of these microhabitats, and others 

move freely between them. Arenivaga grata is found under 

stones and rocks in scrub oak, oak-pine, and oak 

manzanita forests in Texas (Tinkham, 1948), but has been 

reported from bat guano in a cave in Arizona (Ball et al., 

1942). Sand-swimming and Australian burrowing cockroaches 

are frequently found in the root zones of plants. 

Arenivaga investigata is most commonly associated with 

the shrubs Larrea tridentata, Atriplex canescens, and Croton 

californicus (Edney et al., 1978). The burrows of desert 

vertebrates utilized by some cockroach species are also 

typically found near desert plants. In the desert, vegetation 

is a source of shade and food, and subterranean root 

systems concentrate available moisture (Wallwork, 1976). 

About half the desert cockroaches for which we have 

any information live in the burrows of vertebrates (Roth 

and Willis, 1960). Various species of Arenivaga and Polyphaga 

live in the excavations of desert turtles, prairie 

dogs, ground squirrels, wood rats, gerbils, and whitefooted 

mice (Roth and Willis, 1960; Krivokhatskii, 1985). 

In some species, burrows are just one of several utilized 

microhabitats. The blattellid Euthlastoblatta abortiva can 

be found in both wood rat nests and leaves and dry litter 

on the ground along the Rio Grande River in Texas 

(Helfer, 1953). Arenivaga floridensis has been observed 

in the burrows of mice, burrowing freely in loose sand, 

and amid vegetation in sandhill and scrub communities 

(Atkinson et al., 1991). Occasionally only females 

(e.g., Arenivaga erratica—Vorhies and Taylor, 1922) or 

54 COCKROACHES

Fig. 3.10 Distribution of Arenivaga sp. in relation to depth below the surface (A,C) and temperature 

(B,D). In (A) and (C) the insects are scored according to size: open columns 1st–3rd instar; 

striped columns 4th–6th instars; solid columns 7th–9th instars and adults. Adult males 

were rarely found below the surface and are not included in the data set. After Edney et al. (1974). 

Reprinted by permission of the Ecological Society of America. 

nymphs (e.g., Car. lutea—Hubbell and Goff, 1939) are 

collected from burrows. 

Animal burrows generally offer a more favorable microclimate 

than surface habitats. A higher humidity is 

maintained by the respiration of the vertebrate occupant 

(Tracy and Walsberg, 2002), and because of enhanced air 

circulation in burrows, cockroaches that utilize them 

avoid the hypoxic conditions that may be encountered 

by sand-swimming species (Cohen and Cohen, 1981). 

Richards (1971) indicates that animal burrows have a microclimate 

that is intermediate between that of caves and 

that of surface habitats. Recent studies, however, suggest 

that animal burrows are not always cool and humid refugia 

from surface conditions. For more than 100 days of 

the year soil temperatures rose to over 30C at depths of 

2 m in burrows of Dipodomys in the Sonoran desert 

(Tracy and Walsberg, 2002). 

In a remarkable case of niche construction, at least one 

cockroach species mitigates conditions within vertebrate 

burrows by building a home within a home. In southeastern 

Arizona Arenivaga apacha is a permanent inhabitant 

of mounds of the banner-tailed kangaroo rat 

(Dipodomys spectabilis) and builds a microenvironment 

of small burrows (“shelves”) within the main burrow of 

the rat (Cohen and Cohen, 1976). The mini-burrows are 

tightly packed with the grasses that were dragged into the 

main burrow by the rat for use as nesting material. Although 

the rodent burrows extend much deeper, most of 

the cockroaches were found 30–45 cm below the sand 

surface. Surface temperatures reached as high as 60C, 

burrow temperatures reached 48C , but the temperature 

of the grass-lined cockroach shelves averaged 16.5C. Humidity 

of the burrows was as low as 20%, but the shelves 

remained nearly saturated at all times; 91% was the lowest 

reading. Conditions within the vertebrate burrow 

were nearly as harsh as the open desert and were made 

tolerable only by the alterations in the microenvironment 

made by the cockroaches; the insects died in 3–5 min if 

subjected to temperatures above 40C. These cockroaches 

feed on the stored seeds of their host. “With this stored 

food available throughout the year and the very stable environmental 

conditions, the cockroaches have an ideal 

kind of oasis in the midst of a harsh desert environment” 

(Cohen and Cohen, 1976). 

While A. apacha exhibits striking behavioral strategies 

for living in the harsh desert environment, its closely related 

congener, the Colorado Desert sand swimming A. 

investigata, relies heavily on well-developed physiological 

mechanisms. Arenivaga investigata has a higher temperature 

tolerance and lower rates of water loss and oxygen 

consumption than A. apacha (Cohen and Cohen, 1981). 

This is due in large part to the predominance of long 

chain wax esters in the cuticle that are effective in waterproofing 

the insect (Jackson, 1983). Arenivaga investigata 

is also able to tolerate a water loss of 25–30% without 

lethal effects (Edney, 1967) and is able to absorb water vapor 

from the surrounding air at 82% relative humidity 

(RH) (Edney, 1966). This level of RH is available at 45 cm 

below the ground surface (Edney et al., 1974). Thus, descending 

to that level assures the cockroach a predictable 

source of water. Water vapor is absorbed by means of a 

unique system of specialized structures on the head and 

mouthparts (O’Donnell, 1977a, 1977b). A thin layer of 

hygroscopic fluid is spread on the surface of two eversible 

HABITATS 55

Table 3.4. Water balance in Arenivaga. Data are in mg/100 mg/ 

day at 25°C for a 320 mg nymph. From Edney (1966). 

Dry air 

88% RH 

Water loss 

Feces 0.19 0.19 

Cuticular and spiracular 5.43 0.65 

Total 5.62 0.84 

Water gain 

Food 0.22 0.44 

Metabolism 0.87 0.87 

Vapor absorption 0 2.14 

Total 1.09 3.45 

Fig. 3.11 Morphological structures associated with capturing 

atmospheric water in Arenivaga investigata. Top, photograph of 

head showing the two dark, spherical bladders protruding 

from the mouth. Note hairs around edge of pronotum. From 

O’Donnell (1977b), courtesy of M.J. O’Donnell. Bottom, sagittal 

view of the head with portions removed to show details of 

structures; redrawn from O’Donnell (1981), with permission 

of M.J. O’Donnell. The frontal body secretes a fluid that 

spreads over everted hypopharyngeal bladders. Atmospheric 

water condenses in the fluid and both liquids then flow toward 

the esophagus and are swallowed. Arrows indicate route of 

fluid movement from site of production in the frontal bodies 

to the esophagus. 

bladders, one on each side of the mouth (Fig. 3.11). These 

are coated with a thick layer of cuticular hairs that hold 

and distribute the fluid via capillary action. The fluid is 

supplied to the bladders by two glands located on the inside 

of the labrum and embedded in a massive muscular 

complex that can be seen oscillating when the glands are 

secreting fluid. Atmospheric water condenses on the 

bladders and is then transferred to the digestive system, 

where it is absorbed. The capture of atmospheric moisture 

is a solute-independent system, based on the hydrophilic 

properties of the cuticular hairs on the bladders 

(O’Donnell, 1981, 1982). As a result of this water uptake 

system, A. investigata can maintain water balance even if 

no free water is available and food contains only 20% water, 

provided that air at 82% RH or above is available 

(Table 3.4). Females and nymphs are capable of absorbing 

water vapor, but males are not (Edney, 1967). Females 

are apterous, but males are winged and may be capable of 

seeking out free water and higher humidity surface habitats. 

The Egyptian species Heterogamisca syriaca is similarly 

adapted to desert life. A lipid layer effective up to 56C 

protects against evaporation, and the cockroach can extract 

water vapor from unsaturated air between 20 and 

40C and RH 75% (Vannier and Ghabbour, 1983). Humid 

air is available at a depth of 50 cm and at the surface 

during the night. Water absorption presumably occurs 

via hypopharyngeal bladders, as these have been observed 

in H. chopardi (Grandcolas, 1994a). Under the harshest 

conditions of water stress, H. syriaca may fast to generate 

metabolic water from fat reserves, which are abundant 

during the summer months (references in Vannier and 

Ghabbour, 1983). 

Cockroaches that live in arid zones are rich in potential 

for research into behavioral ecology and physiology. 

Thorax porcellana living in suspended litter in dry forests 

of India, for example, do not actively seek or drink water 

56 COCKROACHES

when maintained in laboratory culture (Reuben, 1988), 

and nothing is known about the many diurnal Australian 

species that enjoy sunbasking. Perhaps as in some birds 

(Dean and Williams, 1999) the added heat helps speed digestion 

of a cellulose-based diet. Juvenile Phyllodromica 

maculata live on the dry, grassy hillsides of Bavaria, prefer 

low humidity, and do not aggregate (Gaim and 

Seelinger, 1984). Studies of laboratory-bred cockroaches 

indicate a variety of methods for dealing with heat and 

water stress. Periplaneta americana, B. germanica, and 

Blatta orientalis can withstand a body weight loss of 30% 

and still recover successfully when given an opportunity 

to drink water (Gunn, 1935). Periplaneta fuliginosa and 

R. maderae nymphs use the salivary glands as water storage 

organs (Laird et al., 1972; Appel and Smith, 2002). 

Gromphadorhina brauneri and P. americana maintain 

body temperatures below that of surrounding air by 

evaporative cooling (Janiszewski and Wysocki, 1986), 

and there is some evidence that P. americana can close 

dermal gland openings to conserve water (Machin et al., 

1994). The physiology of water regulation in cockroaches 

is addressed in detail by Edney (1977), Mullins (1982), 

and Hadley (1994). 

Aquatic Habitats 

Most amphibious and quasi-aquatic cockroaches fall into 

two basic groups: those that live in phytotelmata (small 

pools of water within or upon plants) and those associated 

with rivers, streams, and ponds. In both cases, the insects 

live at the surface of the water or on solid substrate 

in its immediate vicinity, but submerge to hunt for food 

or to escape predators. About 62 species (25 genera) of 

cockroaches have been collected from the leaf bases of 

bromeliads (Roth and Willis, 1960; Rocha e Silva Albuquerque 

and Lopes, 1976), but it is unknown how many 

of these are restricted to this habitat. One example is 

Dryadoblatta scotti, a large, handsome, Trinidadian cockroach 

found in considerable numbers in epiphytic bromeliads; 

they rest just above the surface of the water or are 

partly immersed in it (Princis and Kevan, 1955). Nymphs 

of Litopeltis sp. are encountered during the day at all times 

of the year in the erect bracts of Heliconia, which collect 

and hold water even during the dry season of Costa Rica. 

The cockroaches forage at night on the outer and inner 

surfaces of the bracts, feeding on mold and decayed areas 

(Seifert and Seifert, 1976). 

Numerous species in at least six genera of Epilamprinae 

live near streams or pools, usually in association with 

rotting vegetation amid rocks along the edge of the water. 

Poeciloderrhis cribrosa verticalis in Rio de Janeiro (Rocha 

e Silva Albuquerque et al., 1976) and Rhabdoblatta annandalei 

in Thailand (LMR, pers. obs.) occur near swiftmoving 

streams, and Rhabdoblatta stipata in Liberia occurs 

on logs or mats floating directly in the current (Weidner, 

1969). The cockroaches submerge in response to disturbance 

or when a shadow passes overhead, and swim 

rapidly below the surface for a minute or two. They then 

cling to submerged vegetation for up to 15 min before 

climbing to the surface (e.g., Epilampra maya [reported 

as Ep. abdomennigrum] in Panama—Crowell, 1946). 

It has been debated as to whether aquatic cockroaches 

have morphological adaptations that enable underwater 

respiration. In most species observed to date, it appears 

that the insects use the abdominal tip as a snorkel, use a 

bubble of air as an accessory gill, or both. Weidner (1969) 

writes that individuals of Rha. stipata inspire via spiracles 

located on conical projections adjacent to the cerci, and 

die in 6–12 hr if the abdominal tip is held under water. 

Opisthoplatia maculata also has spiracular openings at 

the tip of abdominal projections, and these are protected 

by long hairs on the ventral surface of the cerci (Takahashi, 

1926). Annandale (1906) suggested that the position 

of these posterior spiracles is an adaptation to an 

aquatic lifestyle; however, Shelford (1907) and Chopard 

(1938) point out that this character is present in many 

terrestrial cockroach species. Scanning electron micrographs 

of Ep. abdomennigrum reveal no unique adaptations 

of the terminal spiracles; they appear to be identical 

to those elsewhere on the body (WJB, unpubl. obs.). 

There are distinct patches of hairs on the ventral side of 

the cerci in older nymphs that that are absent in other 

Epilampra species examined; however, these hairs are 

quite distant from the terminal spiracles. The tracheal 

systems of aquatic and terrestrial cockroaches are morphologically 

distinct. The tracheae of the latter are 

thread-like, silvery in appearance, and dilated to their 

maximum with air. The tracheae of amphibious cockroaches 

are strap-like, not silvery, and contain just a few 

scattered air bubbles. Shelford (1916) suggested that the 

differences are rooted in the need for the amphibious 

species to be “sinkable,” which would be prevented by internal 

accumulated air. 

A large bubble is apparent beneath the pronotal shield 

of several aquatic species when they are submerged. The 

air is trapped by easily wetted, long hairs on the underside 

of the thorax (Takahashi, 1926; Crowell, 1946); these 

hairs also occur on terrestrial species. Some observers 

suggest that the bubble is formed by air taken in through 

the terminal abdominal spiracles, which then issues from 

the prothoracic spiracles in Ep. maya and O. orientalis 

(Shelford, 1907; Takahashi, 1926). Although this may explain 

the formation of the thoracic air bubble, air usually 

moves posteriorly through the tracheal system of blaberids 

(Miller, 1981), and recent observations suggest a 

different source of the bubble. WJB (unpubl. obs.) ob- 

HABITATS 57

served 48 dives of Ep. abdomennigrum nymphs in an 

aquarium in Costa Rica. When a nymph swimming on 

the surface is disturbed, it flips 180 degrees, with the venter 

of the body briefly facing upward. While supine the 

cockroach envelops an air bubble with its antennae and 

front legs, and holds the bubble beneath the thorax; the 

antennae remain extended posteriorly between the legs. 

As the cockroach dives below the surface, it turns again, 

righting itself, with the bubble held ventrally. Once underwater, 

it either grasps vegetation to remain submerged, 

or floats slowly to the surface. The median time 

totally submerged was 80 sec (range 20–1507 sec). While 

floating to the surface, the abdomen is extended upward, 

lifting the terminal spiracles out of the water. The insect 

remains motionless while floating on the air bubble 

for up to 30 min as the abdomen pulses slowly, at 1 or 2 

pulses/10 sec. 

Arboreal and Canopy Habitats 

Rainforest canopies are structurally complex habitats 

with many niches favorable for maintaining cockroach 

populations: living and dead leaves, branches, bark crevices, 

sub-bark spaces, vines, epiphytes, suspended soils, 

hollow branches, vine-tree interfaces, treeholes, and bird 

and insect nests, among others. Canopies also contain an 

exceptionally rich array of organic resources (Novotny et 

al., 2003) known to be incorporated into cockroach diets. 

These include nonvascular plants, sap, bird excrement, 

plant litter, leaves, flowers, and fruit. In most studies of 

canopy invertebrates cockroaches are a consistent but minor 

component of the fauna. At times they are relegated 

to the “other” category (e.g., Nadkarni and Longino, 

1990) because of the low number collected. Species-level 

identification is rarely attempted. In a recent eye-opening 

review of canopy arthropods worldwide, however, Basset 

(2001) concluded that while cockroaches represented 

only 5.3% of the individuals collected, they dominated in 

the amount of invertebrate biomass present. Blattaria 

represented 24.3% of the biomass, with Hymenoptera 

(primarily ants) coming in second at 19.8%, and Coleoptera 

ranking third at 18.8%. The revelation that nearly 

a quarter of the arthropod biomass in tree canopies may 

consist of cockroaches is particularly significant because 

the most commonly used canopy techniques almost certainly 

under-sample Blattaria. These are fogging, light 

traps, suspended soil cores, beating foliage, bromeliad 

bagging, and branch bagging (Table 3.5). Fogging is most 

effective on insects out in the open and is typically conducted 

early in the morning when the air is still. At that 

time, however, nocturnal and crepuscular cockroach 

species have likely entered harborage for the day. While 

the insecticide fog might kill them, they may not drop 

from their shelters. The same is true for cockroaches that 

live in tree hollows, epiphytes, insect nests, and other enclosed 

canopy habitats. Light traps, on the other hand, 

capture only volant cockroaches (Basset et al., 2003b) like 

Gyna gloriosa, taken at a height of 37 m in Uganda (Corbet, 

1961). Branch bagging under-represents highly mobile 

taxa, and must be well timed. More cockroaches were 

collected at night than during the day using this method 

(Schowalter and Ganio, 2003), possibly because cockroaches 

perching on leaves during their active period 

were included in the night samples. A combination of the 

above methods may give a clearer picture of cockroach diversity 

and abundance in the canopy, with the additional 

use of baited traps and hand collecting from vines, suspended 

dead wood, treeholes, and other cryptic habitats 

(Basset et al., 1997). There is evidence that canopy cockroaches 

are a taxonomically rich group. In a fogging experiment 

in Borneo cockroaches were about 2% of the 

catch, but 40 presumed species were represented (Stork, 

1991). A difficulty in documenting cockroach diversity, 

however, is that it is rarely possible to identify cockroach 

juveniles, and these can make up the bulk of Blattaria collected; 

90% of the cockroaches collected by Fisk (1983) in 

Central American canopies were nymphs. In Venezuela, 

Paoletti et. al (1991) categorized cockroaches collected in 

their study as “microinvertebrates” because all were less 

than 3 mm in size. It is unclear, however, if these were 

small species or immatures. 

Despite the high amounts of precipitation in rainforests, 

the canopy is a comparatively harsh environment 

characterized by high mid-day temperatures and low 

relative humidities, wind turbulence, and intense solar 

radiation (Parker, 1995; Rundel and Gibson, 1996). Cockroach 

canopy specialists no doubt have physiological and 

behavioral mechanisms that allow them to function in 

these conditions, but we currently have little information 

on their biology. These taxa are distinct from species 

commonly collected near the forest floor by light traps 

and other means (Fisk, 1983), and have been characterized 

as “smaller, aerial varieties endowed with unexpected 

beauty”(Perry, 1986). Conspicuously colored beetle mimics 

like Paratropes bilunata live in the canopy; this species 

imitates both the appearance and behavior of a lycid 

beetle (Perry, 1986). Fisk (1983) considered the following 

blattellid genera as canopy indicators in Panama and 

Costa Rica: Imblattella, Nahublattella, Chorisoneura, Riatia, 

and Macrophyllodromia. In Costa Rican lowland rainforest, 

Schal and Bell (1986) collected Car. imitans and 

two species of Imblattella from attached, folded, dead 

leaves in successional stands, and noted Nyctibora noctivaga 

and Megaloblatta blaberoides on trees in mature forest. 

Most studies of canopy invertebrates have been con- 

58 COCKROACHES

Table 3.5. Studies in which cockroaches were collected during canopy sampling. 

Method Location Habitat Reference 

Beating foliage Gabon Lowland rainforest Basset et al. (2003a) 

Branch bagging Puerto Rico, Evergreen wet forest Schowalter and Ganio (2003) 

Panama 

Bromeliad bagging Venezuela Cloud forest Paoletti et al. (1991) 

Bromeliad bagging Mexico Low, inundated forest, Dejean and Olmstead (1997) 

semi-evergreen forest 

Fogging Sabah Lowland rainforest Floren and Linsenmair (1997) 

Fogging Australia Rainforest Kitching et al. (1997) 

Fogging Japan Mixed pine stand Watanabe (1983) 

Fogging Brunei Lowland rainforest Stork (1991) 

Fogging Thailand Dry evergreen forest Watanabe and 

Ruaysoongnern (1989) 

Fogging Hawaii Varied; altitudinal transect Gagné (1979) 

Fogging Costa Rica, Lowland forest Fisk (1983) 

Panama 

Light traps Sarawak Lowland mixed Itioka et al. (2003) 

dipterocarp forest 

Suspended soil Gabon Lowland forest Winchester and Behancores 

Pelletier (2003) 

ducted in the tropics. The canopies of temperate forests 

have proportionately fewer niches available because of 

the lower occurrence of lianas and epiphytes (Basset et al., 

2003b; Novotny et al., 2003). In Japan, no cockroaches 

were listed in the results of a fogging study on a cypress 

plantation (Hijii, 1983) but they were recovered from a 

mixed pine stand (Watanabe, 1983). Miriamrothschildia 

( Onychostylus) pallidiolus is an arboreal cockroach in 

Japan, the Ryuku islands, and Taiwan. The nymphs are 

very flat and semitransparent, and are found on live or 

dead tree leaves (Asahina, 1965). In the United States 

(South Carolina) Parcoblatta sp. were present in dead 

limbs and in and on the outer bark of longleaf pines sampled 

in winter. All trees had cockroaches on the upper 

bole, with a mean biomass of 36.2 mg/m 2 . Cockroaches 

were present but variable on other parts of the tree 

(Hooper, 1996). Additional Blattaria that forage and shelter 

on live and dead tree boles at various heights include 

Aglaopteryx gemma (Horn and Hanula, 2002) and several 

species of Platyzosteria on tea tree (Leptospermum) in 

Australia (Rentz, 1996). 

A number of species that shelter on or near the forest 

floor spend their active period on trunks or low branches 

(Schal and Bell, 1986). However, Basset et al. (2003a) reported 

no difference in the number of cockroaches collected 

between day and night beat samples in lowland 

tropical rainforest in Gabon. Seasonal movement into the 

canopy may occur, coincident with rainfall and its effects 

on tree phenology. In Central America, Fisk (1983) collected 

16 arboreal cockroach species (n 220) during the 

dry season, but 24 species (n 986) during the wet season. 

Maximum cockroach numbers coincided with peak 

new leaf production of the early wet season. In a light 

trapping study in Sarawak, Itioka et al. (2003) monitored 

cockroach abundance in relation to flowering periods in 

the canopy. Blattaria were most numerous during the 

post-flowering stage, and lowest during the non-flowering 

stage (Fig. 3.12). This seasonal abundance was attributed 

to the increased amount of humus in the canopy 

during the post-flowering period, derived from spent 

flowers, fruits, and seeds. Barrios (2003) found that the 

number of cockroaches collected by beat sampling comparable 

leaf areas in Panama was higher in mature trees 

(n 237) than in saplings (n 60). Long-term fluctuations 

were evident in a study by Schowalter and Ganio 

(2003). Canopy cockroaches were more abundant in 

drought years, and least abundant during post-hurricane 

years in Puerto Rico and Panama. 

There are numerous humid microhabitats in treetops, 

where cockroaches not specifically adapted to the arid 

conditions of the canopy thrive. Among these are habitats 

that are little or nonexistent in the understory, such as 

bird nests and the spaces in and around complex vegetation 

such as epiphytes, intertwining vines, lianas, tendrils, 

HABITATS 59

Fig. 3.12 Average monthly numbers of cockroaches in light 

traps at 1, 17, and 35 m in height during three trapping periods; 

flowering status of the trees varied during these periods. 

The study was conducted in tropical lowland dipterocarp forest 

in Sarawak, Malaysia. After Itioka et al. (2003), with permission 

of T. Itioka. 

and adventitious roots. These provide sheltered resting 

places and a substantial amount and variety of food, particularly 

in the form of suspended soils. Fisk (1983) found 

a general albeit inconsistent correlation between number 

of cockroaches collected during fogging and the number 

of lianas per tree. Floren and Linsenmair (1997) fogged 

trees from which all lianas and epiphytes were removed in 

Sabah, and found that cockroaches did not exceed 1% of 

the insects collected, on average. The substantial pool of 

suspended soil that accumulates in the various nooks and 

crannies of the canopy may be particularly important in 

understanding the vertical stratification of cockroach 

faunas (Young, 1983), yet it is commonly neglected in 

tropical canopy research (Winchester and Behan-Pelletier, 

2003). Suspended soil has a high organic content derived 

from leaf, fruit and flower litter, epiphyte tissues, decomposing 

bark, and the feces, food, and faunal remains 

of canopy-dwelling animals. It also contains a mineral 

component derived from fine particles carried on wind, 

rain, and fog (Winchester and Behan-Pelletier, 2003). 

This above-ground humus in rainforest is often thicker 

than the rapidly decomposing layer on the ground, and 

cockroaches that utilize the plant litter on the forest floor 

may also do so in the litter of the canopy. Leaf litter in 

plastic cups suspended in the lower branches of cacao 

trees in Costa Rica attracted cockroaches. Most abundant 

were species of Latiblattella and Eurycotis; the latter was 

also found in ground litter (Young, 1983). Studies of 

arthropods to date, however, generally indicate that the 

soil/litter fauna on the forest floor is in large measure distinct 

from that of the forest above (Basset et al., 2003b). 

One example among cockroaches is Tho. porcellana, 

which lives in aerial litter caught by the interlaced horizontal 

branches of plants in scrub jungle in India. The entire 

lifecycle of this cockroach is confined to suspended 

soil; they have no direct contact with the substratum 

(Bhoopathy, 1997).Winchester and Behan-Pelletier (2003) 

found that unidentified cockroaches collected from suspended 

soil cores from the crown of an Ongokea gore tree 

in Gabon were stratified; they were more abundant at 42 

m than at 32 m above the ground. 

Canopy litter is often considered ephemeral, as it can 

be removed by disturbances such as wind, rain, and arboreal 

animals (Coxson and Nadkarni, 1995). That is not 

true of the suspended soil trapped in some of the container 

epiphytes, such as the bird’s nest Asplenium ferns 

and species of Platycerium with basal, clasping structures. 

In both, the litter mass acts as a sponge to retain water and 

nutrients (Rundel and Gibson, 1996). In the Neotropics 

epiphytes and hemiepiphytes may comprise greater than 

60% of all individual plants, individual trees may support 

several hundred bromeliads, and a single bromeliad can 

contain more than 100 gm of soil (Gentry and Dodson, 

1987; Paoletti et al., 1991). This is a substantial resource 

pool for cockroaches that feed on the accumulated debris 

and microorganisms contained within. Dejean and Olmsted 

(1997) found cockroaches in 67–88% of collected 

bromeliads (Aechmea bracteata) examined on the Yucatan 

peninsula of Mexico. Rocha e Silva Albuquerque et 

al. (1976) identified more than 30 cockroach species in 

bromeliads and list additional ones from the literature. 

60 COCKROACHES

FOUR 

Diets and Foraging 

Timid roach, why be so shy? 

We are brothers, thou and I. 

In the midnight, like yourself, 

I explore the pantry shelf! 

—C. Morley, “Nursery Rhymes for the Tender-Hearted” 

Cockroaches are typically described as omnivores, scavengers, or “classic generalists” 

(Dow, 1986), insects that feed on most anything they encounter. Indeed, the success of 

pest cockroaches in human habitations may be based largely on their ability to feed on 

soap, glue, wire insulation, and other materials that they certainly did not encounter during 

their evolution and do not encounter while living in more natural habitats. Our 

knowledge of cockroach diets stems largely from studies of these domestic pests, and it 

is assumed that their dietary habits are the norm (Bell, 1990). Some non-pest species 

(e.g., certain cave cockroaches) do appear omnivorous, but the term is not an adequate 

descriptor for the majority of Blattaria. Outside the man-made environment, the cockroach 

diet typically contains more refractory material than is generally appreciated 

(Mullins and Cochran, 1987). They can be selective eaters, and in some cases, specialized. 

There are several reasons for this rather biased image of cockroach diets. Some species 

will eat almost anything in urban or laboratory settings, but are highly selective in the 

wild. Few feeding observations or gut analyses from cockroaches in natural habitats have 

been conducted; in existing studies the picture is far from complete. We may have an indication 

of the menu at a particular point in time; however, we do not know if the food 

item in question is a small or large component of the diet. Further, the menu may vary 

with availability of certain foods, and with the age, sex, and reproductive or developmental 

status of the consumer. 

FORAGING BEHAVIOR 

With some exceptions, three feeding syndromes characterize the cockroaches that can be 

observed from ground level in tropical rainforest. First, nymphs of most species become 

active at nightfall, and begin to forage in the leaf litter on the forest floor. They can be 

seen skeletonizing wet, dead leaves, leaving harder veins and similar tissue. Leaf chips or 

dead leaf mush dominate the gut contents, but nematodes, fungi, insect larvae, and 

61

oligochaetes are also found. This feeding strategy was 

confirmed in the laboratory, where cockroach nymphs 

were observed ingesting the entire “sandwich”: the leaf 

and everything on it (WJB, pers. obs.). Second, adults 

emerge from tree holes, leaf litter, and other harborages, 

and begin a vertical migration up into the canopy; the 

heights reached are species specific and probably relate to 

nutritional preferences (Schal and Bell, 1986). When the 

adults have reached the “correct” height, they move onto 

leaves and begin feeding on materials that have fallen or 

grow on the leaves. Third, a subset of species, mostly blattellids, 

shelter in curled dead leaves at a height of 1.5 to 2 

m; palm fronds are commonly chosen as harborage. At 

night the cockroaches flit about leaves in the canopy, 

scraping algae and other microvegetation from the phylloplane. 

These species do not feed at a preferred height. 

Other foraging strategies include feeding on bark and 

epiphylls of rotting logs (Capucina) and feeding in rotting 

wood (nymphs of Megaloblatta). Some species have never 

been observed feeding, such as the green cockroach 

Panchlora nivea, but their guts contain a sweet-smelling 

substance that may be nectar from the upper canopy 

(WJB, pers. obs.) 

Locating Food 

Individually marked cockroaches in the rainforest generally 

home in on food via exploration and olfactory cues, 

sometimes arriving at fruit falls from quite long distances 

(Schal and Bell, 1986). Once near the food item, the cockroach’s 

antennae and palps are used to inspect the resource; 

the information gathered is then used as basis to 

decide whether ingestion should proceed (WJB, unpubl. 

data). In domestic species (Blattella germanica), food 

closest to the harborage is exploited first (Rivault and 

Cloarec, 1991); this is probably also the case for cockroaches 

in natural habitats. 

Individuals of Diploptera punctata in Hawaii are attracted 

to moist, dead leaves (WJB and L.R. Kipp, unpubl. 

obs.). Experiments were conducted on a large (2 m tall) 

croton bush in the late afternoon, during the inactive period 

of the cockroach. The insects previously had been 

seen foraging in the bush at 9:00 the same morning. Dead, 

wet leaves were placed on a branch about 1.2 m from the 

ground, and within 5 min individuals appeared near the 

bait leaves, apparently lured from their harborages at 

the base of the plant by the leaf odor. When “activated” by 

the odor they scurried about, waving their antennae. 

When a branch route took them near, but not to the dead 

leaf, they would get to the end of the branch, antennate 

rapidly, then turn and run down the branch to seek another 

route. Sometimes an individual made several attempts, 

over various routes, before locating the wet leaf. 

They were never observed flying to the bait. In Hawaii, D. 

punctata foraged from early evening (6:00 p.m.) to midmorning 

(10:00 a.m.), with two peaks in activity at 8:00 

a.m. and 10:00 p.m. Nonetheless, the cockroaches could 

be activated to return to the above-ground portions of the 

plant at any time by hanging new decaying leaves within 

the canopy. Members of this population survived and reproduced 

for 6 mon in WJB’s laboratory in Kansas on a 

diet consisting solely of dead oak and hackberry leaves. 

Relocating Food 

Urban cockroaches (B. germanica) search individually 

and independently for food. Items are not transported 

back to shelter, but eaten where they are found (Durier 

and Rivault, 2001a). In at least two cockroach groups the 

place where food is acquired differs from where it is utilized. 

Obtaining food and using it are thus separated in 

time and space, and the obtainer and the user are not necessarily 

the same individual (Zunino, 1991). Both groups 

that employ this “grocery store” strategy live in excavated 

underground chambers. The Australian soil-burrowing 

cockroaches forage during the night and the early morning 

hours of the wet season. After a rain and above a certain 

threshold temperature, they emerge, transport a 

quantity of dead leaves down into the burrow, and then 

do not emerge again until the next rain. Females grasp a 

food item in their mandibles and drag it backward down 

into the burrow. If they are approached when they are on 

the surface they will drop whatever they are carrying and 

“get a fair scuffle up” running back to their burrow (D. 

Rugg, pers. comm. to CAN). Gathered leaves are eaten by 

both the forager and any young offspring in the nest. 

Nymphs begin provisioning their own burrow when they 

are about half-grown. The food cache accumulated during 

the rains must sustain burrow inhabitants throughout 

the dry season (Rugg and Rose, 1991, pers. comm. to 

CAN). Other cockroaches known to transport and store 

food live in the tunnels of small vertebrates. Arenivaga 

apacha in the burrows of kangaroo rats in Arizona can be 

found nesting amid Yucca, Ephedra, Atriplex, and grass 

seeds that they have filched from the supply gathered and 

stored by the host rodent. “Our suspicion that the cockroaches 

gather and hoard provisions was confirmed when 

we saw the cockroaches carry dried dog food and sesame 

seeds that were sprinkled over the top of the aquaria soil 

into small caches underground” (Cohen and Cohen, 

1976). 

There are records of other cockroach species transporting 

food, but in these cases it occurs only in competitive 

situations. Rivault and Cloarec (1990) discovered 

that B. germanica began to “steal” food items from a dish 

as the items became small enough to carry and as food be- 

62 COCKROACHES

came scarce. Adults and larger nymphs stole more food 

than younger nymphs, and more stealing occurred when 

two or more individuals were present at a food source 

than when a lone individual was feeding. Similarly, when 

LMR fed crowded laboratory cultures with rice, he observed 

young nymphs position individual pieces of it between 

their front legs and mouthparts and run off on 

their hind legs (identity of species is lost to memory). Annandale 

(1910) documented Periplaneta americana using 

the mandibles to seize, hold, and transport termite alates 

in Calcutta. 

Competition at food sources can trigger intraspecific 

aggression in B. germanica. The insects vary their tactics 

with age, and tailor them to the developmental stage of 

the opponent. Most agonistic interactions are between individuals 

of the same developmental stage.Young nymphs 

are primarily biters, but begin kicking more often as they 

develop; a good boot becomes more effective with the increased 

body weight characteristic of older stages (Rivault 

and Cloarec, 1992c). Young nymphs are generally tolerated 

by older stages and often reach food by crawling 

beneath larger conspecifics (Rivault and Cloarec, 1992a, 

1992b). The relative amount of food required by large 

and small nymphs lowers the cost of benevolence for 

older insects. 

Food relocation and aggression are both proximate 

mechanisms for obtaining and securing food from competitors. 

In burrow dwellers, relocation also allows them 

to feed at leisure in a location relatively safe from predators. 

Resource competition also may influence life history 

strategies, resulting in the distribution of competitors 

within a guild either in time (Fig. 3.5) or in space. 

Learning 

In many species, the location of the night harborage is 

spatially separated from other resources such as food and 

water. In the laboratory and in urban settings, individuals 

of B. germanica learn the position of their shelter and 

of stable food sources in relation to visual landmarks; 

however, olfactory information, which provides more reliable 

information about the presence of food, can override 

the visual cues. The insects learned to associate a certain 

type of food with a specific site, and were “disturbed” 

(exhibited complex paths) when the association between 

food type and food position was modified (Durier and 

Rivault, 2001b). Young nymphs of this species tend to explore 

smaller areas, cover shorter distances, and remain 

longer at depleted food sources than older cockroaches, 

eventually learning that “there is no point in waiting near 

a depleted patch, as it will not be renewed immediately” 

(Cloarec and Rivault, 1991). Periplaneta americana is differentially 

attracted to various dietary nutrients, and 

learned to associate certain odors with a proteinaceous 

food source, particularly when they were protein deprived. 

No such association between odor and carbohydrate 

could be established (Gadd and Raubenheimer, 

2000). Watanabe et al. (2003) demonstrated that P. americana 

can be classically conditioned to form olfactory 

memories. The species also begins including novel foods 

in its diet after nutrient imbalances (Geissler and Rollo, 

1987). It is probable that similar associations occur in nature; 

cockroach species known to have a wide dietary 

repertoire may both acquire knowledge of food-associated 

odors and benefit from past experience. 

FEEDING VARIATION AND FOOD MIXING 

Urban pest cockroaches (Supella longipalpa), like many 

omnivores (Singer and Bernays, 2003), balance their diet 

by selecting among available foods rather than by trying 

to obtain all nutrients from one food type (Cohen et al., 

1987). Periplaneta fuliginosa is described as a “cafeteriastyle 

eater” that will sample several types of food before 

concentrating on one (Appel and Smith, 2002). Other 

species known to have a varied diet in natural habitats, 

like Parcoblatta (Table 4.1), may do the same thing. Laboratory 

studies indicate that cockroaches are capable of 

selecting their diet relative to nutrient demand at every 

point in the lifecycle. Within a species, foraging behavior 

and dietary preferences vary with sex and ontogeny, and 

undergo dramatic changes correlated with reproductive 

and developmental cycles. In the field, it is possible that 

these predilections are also influenced by the seasonal 

availability of specific foods. Just after a local mast fruiting, 

for example, their diet may be higher in sugars and 

yeasts, and lower in fiber. When fruit is not available or 

their needs change, they may rely on less nutritious, 

higher-fiber foods such as litter or bark, or seek items that 

provide specific nutrients. 

Age 

As in most young animals (Scriber and Slansky, 1981; 

White, 1985) the dietary requirements of young cockroach 

nymphs differ from those of older nymphs and 

adults. Cochran elegantly demonstrated this in his studies 

of Parcoblatta spp., cockroaches that void urates to the 

exterior in discrete pellets if dietary nitrogen levels exceed 

a certain “break even” point with respect to nitrogen demands. 

In nymphs less than 1 mon old, a diet of 4% nitrogen 

results in only minimal urate excretion. On the 

same diet, nymphs 1–2 mon old void urates at a rate of 

8–13% of excreta by weight and large nymphs reach 

an equilibrium at less than 1.5% nitrogen in the diet 

(Cochran, 1979a; Cochran and Mullins, 1982). In nu- 

DIETS AND FORAGING 63

merous species, this high requirement for nitrogen is reflected 

in the behavior of neonates, whose first meals are 

largely derived from animal or microbial sources. In 

many species the first meal consists of the embryonic 

membranes and the oothecal case. The female parent may 

provide bodily secretions originating from glands in or 

on the body, or from either end of the digestive system 

(Chapter 8). The few studies of coprophagy to date indicate 

that this behavior is most prevalent in early instars, 

suggesting that microbial protein is a crucial dietary component 

(Chapter 5). The need for animal or microbial 

protein may help explain why it is difficult to rear many 

cockroaches in the laboratory. While adults may thrive, 

“nymphs are more difficult to rear, starving to death in 

the midst of a variety of food stuffs” (Mackerras, 1970). 

As they develop, juveniles may adopt the same diet as 

adults (e.g., wood, guano in caves) or feed on different 

materials, such as the rainforest species in which nymphs 

feed on litter but adults have a more varied menu. Studies 

in laboratory and urban settings indicate ontogenetic 

changes in foraging behavior, as well as variation in feeding 

behavior and food choice within a stadium. Immediately 

after hatch nymphs of B. germanica are able to find 

food and return to shelter, but they improve their foraging 

performance as they age (Cloarec and Rivault, 1991). 

Periplaneta americana nymphs take large meals during 

the first three days post-molt, then feed very little until 

the next (Richter and Barwolf, 1994). Juveniles of Su. 

longipalpa change their dietary preferences within a stadium. 

Protein consumption remains relatively low and 

constant, whereas carbohydrate consumption is highest 

during the first week, then declines gradually until the 

end of each instar (Cohen et al., 1987) (Fig. 4.1A). When 

given a wide range of protein:carbohydrate choices, Rhyparobia 

maderae nymphs consistently selected a ratio of 

approximately 25:75, suggesting that they have the ability 

to balance their diet (Cohen, 2001). Subadults of B. germanica 

are impressively capable of compensating dietary 

imbalances by choosing foods that redress deficiencies 

(Raubenheimer and Jones, 2006). 

Sexual Differences 

Current evidence suggests that male foraging behavior 

and food choice differs from that of females; generally, 

male cockroaches feed less and on fewer food types. In the 

Costa Rican rainforest male cockroaches always have less 

food in their guts than do females after the usual nightly 

foraging period (WJB, unpubl. data). This is particularly 

true for seven species of blattellids, in which 50–100% of 

males had empty guts. In more than 30 male Latiblattella 

sp. examined, none had any food in the gut. In contrast, 

males of four species of blaberids often had medium to 

full guts, although females had still fuller guts. This difference 

may be due to the active mate searching required 

of blattellid males as compared to blaberids. Male cockroaches 

tend to have narrower diets than females (Table 

4.2), which may relate to the nutrients required for oogenesis. 

A similar pattern was obvious in D. punctata in 

Hawaii; 44% of females had guts filled to capacity, 

whereas male guts were never full. Nymphal guts were 

variable (19% full, 81% not full). It appeared that first instars 

had not fed at all, suggesting that they were relying 

on fat body reserves developed in utero while being fed by 

their viviparous mother. Older nymphs had fed to repletion. 

In all stages, the gut content was homogeneous material 

resembling dead leaf mush (WJB, unpubl. data). 

The amount of food consumed by male P. americana 

varies greatly on a daily basis, with the insects fasting on 

approximately one-third of days (Rollo, 1984b). Male 

German cockroaches did not exhibit cyclical feeding patterns, 

but the degree of sexual activity appears influential. 

Table 4.1. Diet of four species of Parcoblatta, based on 45 nocturnal observations of feeding adults 

(Gorton, 1980). Note that two species were not observed ingesting animal food sources. 

Parc. pennsylvanica Parc. uhleriana Parc. lata Parc. virginica 

Mushrooms 

Cambium 

 

Flower petals 

 

Moss 

 

Sap 

Cercropid spittle 

 

Live insect 

 

Bird feces 

 

Mammalian feces 

 

Mammalian cartilage 

 

64 COCKROACHES

pregnant females of D. punctata, gut fullness varies relative 

to embryo length, with a trend toward full guts when 

embryos are small (2–5 mm) and empty guts when embryos 

are large (6–8 mm) (WJB, unpubl. data). 

Females in at least two blattellid species select among 

various food types according to their vitellogenic requirements. 

In choice experiments with Xestoblatta 

hamata, Schal (1983) found that high-nitrogen foods 

were consumed mainly on nights 3 and 4 of the ovarian 

cycle. Females of Parc. fulvescens given one high-protein 

and two low-protein diets fed so that they remained in nitrogen 

balance; relative proportions of the different nutrients 

varied over the reproductive cycle (Fig. 4.1B). Females 

with access to only high-protein diets excreted 

urates, an indication that ingested protein levels exceeded 

their needs. Ovarian cycles of the self-selecting individuals 

were similar in length to those of the females fed 

a high-protein diet (Cochran, 1986b; Lembke and Cochran, 

1990). 

STARVATION 

Fig. 4.1 Dietary self-selection in cockroaches. (A) Mean intake 

of protein and carbohydrate (CHO) cubes and cumulative percent 

molting in Supella longipalpa first instars over the course 

of the stadium. From Cohen et al. (1987), courtesy of Randy W. 

Cohen. (B) Food consumption by adult female Parcoblatta fulvescens 

over the course of the reproductive cycle when given a 

dietary choice. Dashed line, 5% protein-cellulose diet; dotted 

line, 5% protein-dextrose diet; solid line, 42% protein diet. EC, 

egg case formation; ECD, egg case deposition. From Lembke 

and Cochran (1990), courtesy of Donald G. Cochran. Both 

graphs reprinted with permission of Elsevier Press. 

The food intake of B. germanica males mated twice per 

week was greater than that of males allowed to mate only 

once (Hamilton and Schal, 1988). 

In many oviparous females, food intake and meal type 

is correlated with the ovarian cycle. Food intake falls to 

a low level a few days prior to ovulation and remains 

low until the ootheca is deposited in P. americana (Bell, 

1969), Parcoblatta fulvescens, Parc. pennsylvanica (Cochran, 

1986b), Su. longipalpa (Hamilton et al., 1990), and B. 

germanica (Cochran, 1983b; Cloarec and Rivault, 1991; 

Lee and Wu, 1994). Water intake is also cyclical (Fig. 4.2) 

(Cochran, 1983b, 1986b). In the ovoviviparous R. maderae, 

food intake declines at the time of ovulation and remains 

at a relatively low level until partition; neural input 

from mechanoreceptors in the wall of the brood sac directly 

inhibits feeding (Engelmann and Rau, 1965). In 

Willis and Lewis (1957) determined the mean survival 

times of 11 species of cockroaches deprived of food, water, 

or both (Table 4.3). When deprived of food and water, 

the insects can live from 5 days (male Blattella vaga) 

to 42 days (female P. americana). When given dry food 

Table 4.2. Gut contents of cockroaches collected between 

20:00 and 4:00 at La Selva Research Station, Costa Rica, between 

January and May 1992 (WJB and J. Aracena, unpub. data). 

Cockroach species n Material in foregut 

Blaberidae 

Capucina rufa 

Male 5 Epiphylls 

Female 2 Epiphylls, bark scraps 

Nymph 6 Epiphylls, bark scraps 

Epilampra rothi 

Male 64 Dead leaf chips 

Female 20 Algae, green plant, dead leaf, 

trichomes 

Nymph 80 Dead leaf chips, insect parts 

Blattellidae 

Xestoblatta hamata 

Male 16 Dead leaf, bird dung 

Female 11 Inga bark chips, algae, dead 

leaf chips, fruit, leaf debris 

Nymph 25 Finely ground dead leaf, 

insect parts 

Cariblatta imitans 

Male 16 Algae 

Female 10 Algae 

Nymph 4 Algae 


Fig. 4.2 Feeding and drinking cycles in relation to the reproductive 

cycle of the wood cockroach Parcoblatta fulvescens. 

Filled circles, water consumption; open squares, food consumption; 

EC, egg case formation; ECD, egg case deposition. 

From Cochran (1986b), courtesy of Donald G. Cochran, with 

permission from Elsevier Press. 

but no water, they lived for about the same period of time 

as those deprived of both. If they are provided with water, 

most lived longer. Some species can live for 2 to 3 mon 

on water alone, and others significantly longer. Virgin females 

of Eublaberus posticus live an average of 360 days on 

water alone, whereas starved but mated females can live 

an average of 8 mon and are even able to produce 1 or 2 

litters, yielding about 26 young. One female mated at 

emergence was starved for 252 days, during which time 

she produced 2 litters totaling 50 nymphs. She was then 

given food on day 252 (and thereafter), mated again 4 

days later, and lived an additional 525 days, producing 5 

more oothecae from which 24, 18, 5, 1, and 0 nymphs 

hatched. Although this female had been starved for the 

first 8 mon of adult life, after food was made available she 

managed to give birth to a total of 98 offspring, which is 

about normal for this species (Roth, 1968c). 

There is a significant difference in starvation resistance 

between males and females in cockroach species exhibiting 

sexual dimorphism in body size. In Table 4.3, males 

and females are of similar size only in Neostylopyga rhombifolia, 

Eurycotis floridana, and Nauphoeta cinerea; in 

these cases, survival of males and females is similar. In the 

remaining species males are significantly smaller than females 

and are more vulnerable to starvation. A larger 

body size is correlated with bigger fat bodies and their accumulations 

of carbohydrates, lipids, and uric acid; these 

reserves can be rapidly mobilized on demand (Mullins 

and Cochran, 1975b; Downer, 1982). The nutrients and 

water housed in developing oocytes are additional resources 

available to starving females. The strategy for a 

food-deprived female of P. americana seems to involve resorption 

of yolk-filled eggs, storage of their yolk proteins, 

and then rapid incorporation of protein into eggs when 

feeding re-ensues (Roth and Stay, 1962b; Bell, 1971; Bell 

and Bohm, 1975). 

A variety of digestive attributes help cockroaches 

buffer food shortages. The large crop allows an individual 

to consume a substantial quantity of food at one time. 

This bolus then acts as a reservoir during periods of fasting. 

When fully distended with food, the crop is a pearshaped 

organ about 1.5 cm in length and 0.5 cm at its 

widest part (in Periplaneta australasiae). It extends back 

to the fourth or fifth abdominal segment, crowding the 

other organs and distending the intersegmental membranes. 

A meal may be retained in the crop for several 

days (Abbott, 1926; Cornwell, 1968). Solid food is also retained 

in the hindgut of starving P. americana for as long 

as 100 hr, although the normal transit time is about 20 hr 

(Bignell, 1981); this delay likely allows microbial biota to 

more thoroughly degrade some of the substrates present, 

particularly fiber. The functional significance of intestinal 

symbionts increases in times of food deficiency and helps 

to maintain a broad nutritional versatility (Zurek, 1997). 

A starving cockroach is thus indebted to its microbial 

partners on two counts: first, for eking out all possible nutrients 

in the hindgut, and second, for mobilizing uric 

acid stored in the fat body (Chapter 5). When food is 

again made available, starved P. americana binge. After 

starving for 13 days the amount of food consumed rose 

to five times the normal level, then leveled off after approximately 

20 days. Greater consumption was accomplished 

by larger and longer meals, not by increasing the 

number of foraging trips (Rollo, 1984a). 

PLANT-BASED FOOD 

There is little evidence that any cockroach species is able 

to subsist solely on the mature green leaves of vascular 

plants. There are reports of occasional herbivory, such as 

that of Crowell (1946), who noted that the small, round 

leaves of the aquatic plant Jussiaca are included in the diet 

of Epilampra maya. Often, cockroaches that appear to be 

feeding on green leaves are actually eating either a small, 

dead portion at the leaf edge or around a hole, or other 

material on the leaf (WJB, unpubl. obs.). To test the extent 

to which tropical cockroaches include fresh vegetation 

in their diets, WJB set up a series of two-choice tests 

in laboratory cages at La Selva Biological Station in Costa 

Rica. Ten species of cockroaches were tested: Capucina 

sp., Cariblatta imitans, Epilampra involucris, Ep. rothi, Ep. 

unistilata, Latiblattella sp., Imblattella impar, Nahublattella 

sp., Nesomylacris sp., and X. hamata. The insects were 

offered a choice of green leaves versus dead leaves of the 

same plant species; only leaves eaten readily by local Or- 

66 COCKROACHES

Table 4.3. Longevity of cockroaches on starvation diets.Tests were performed at 36–40% relative 

humidity, except for tests with R. maderae, which were run at 70%. Note that controls ( food, 

water) are not adult lifespans; controls were terminated when all the experimental insects of 

the species died. Modified from Willis and Lewis (1957). 

Mean length of survival (days) 

food food food food 

Species Sex water water water water 

Blattidae 

Blatta orientalis Female 64 16.8 32.1 14.2 

Male 40 11.5 20.0 11.9 

Neostylopyga rhombifolia Female 108 25.4 26.7 22.1 

Male 128 24.6 29.3 21.9 

Periplaneta americana Female 190 40.1 89.6 41.7 

Male 97 27.3 43.7 28.1 

Eurycotis floridana Female 86 26.6 43.0 26.7 

Male 70 21.8 29.7 21.1 

Blattellidae 

Blattella germanica Female 85 11.9 41.9 12.8 

Male 54 8.8 9.6 8.2 

Blattella vaga Female 95 7.9 32.4 8.5 

Male 69 5.4 16.8 4.8 

Supella longipalpa Female 80 12.8 14.3 14.5 

Male 74 11.5 10.1 9.0 

Blaberidae 

Diploptera punctata Female 102 18.7 42.9 18.7 

Male 119 14.5 28.9 15.8 

Rhyparobia maderae Female 181 160.0 54.3 51.3 

Male 150 84.0 56.0 35.1 

Nauphoeta cinerea Female 98 24.3 61.1 27.0 

Male 94 22.8 46.1 27.3 

Pycnoscelus surinamensis Female 139 18.8 73.2 24.3 

Male 74 9.9 39.8 10.6 

thoptera were used. The feeding behavior of the cockroaches 

was observed throughout the night, and their 

guts dissected the next day. Without exception, no cockroach 

ate fresh vegetation. Individuals that nibbled the 

greenery appeared repelled and on occasion could be observed 

jumping away from the leaf. When offered a choice 

of paper versus green leaves, the cockroaches ate the paper. 

When only green leaf was offered, they refused to 

feed. 

Nonetheless, there are numerous records of cockroaches 

as plant pests (Roth and Willis, 1960). In 1789, 

Captain William Bligh had to wash down his ships with 

boiling water so that cockroaches would not destroy the 

breadfruit trees he was transporting from Tahiti to the 

West Indies (Roth, 1979a). One of the more frequently reported 

plant pests is Pycnoscelus surinamensis, which destroyed 

the roots of 300,000 tobacco plants in Sumatra. In 

greenhouses, it is known to girdle rose bushes, eat the 

bark and stems of poinsettias, and damage orchids, cucumbers, 

and lilies. It was responsible for the destruction 

of 30,000–35,000 rose plants in one Philadelphia greenhouse, 

and regularly hollows the hearts of palms and 

ferns in the southern United States (Roth, 1979a). Apparently, 

it managed to sneak into Biosphere 2 and took a 

strong liking to every kind of living plant. Tomatoes, 

sweet potato leaves, flowers and fruit of squash plants, 

rice seedlings, ripe papayas and figs, and green sorghum 

seeds were each included on the bill of fare (Alling et al., 

1993). While the culprit cockroach was never identified, 

both Pyc. surinamensis and P. australasiae were found in 

the beehives brought in to pollinate crops (Susan C. 

Jones, pers. comm. to CAN). 

The most commonly reported type of plant damage by 

cockroaches is to seedlings, new leaves, and growing root 


and shoot tips. These are likely preferred because their actively 

growing tissues have physically tender, thin-walled 

cells, lower levels of secondary compounds, and higher 

levels of nitrogen than mature leaves (Chown and Nicolson, 

2004). Examples include P. americana destroying 

30% of the freshly planted seeds of the quinine-producing 

plant Cinchona pubescens in Puerto Rico (Roth, 

1979a), and Shelfordina ( Imblattella) orchidae damaging 

developing roots and shoots of orchids in Australian 

greenhouses (Rentz, 1987). Calolampra elegans and Cal. 

solida (Blaberidae) are pests requiring control measures 

in a variety of Australian crops, including sunflower, soybean, 

sorghum, cotton, navy beans, wheat, and maize. 

The cockroaches live in litter and the upper layers of soil, 

and emerge at night to chew the stems of seedlings at or 

near ground level (Robertson and Simpson, 1989; Murray 

and Wicks, 1990; Roach and Rentz, 1998). Cockroach 

herbivory in tropical forests is probably more common 

than generally realized; damage to newly flushed leaves in 

the canopy of Puerto Rican rainforest has been correlated 

with the abundance of cockroaches (Dial and Roughgarden, 

1995). 

Overt herbivores are not limited to feeding on green 

leaves of vascular plants; the category includes organisms 

that feed on other plant parts as well (Hunt, 2003). Many 

cockroach species, then, are at least partly herbivorous, 

because they include pollen, nectar, sap, gum, roots, bark, 

twigs, flowers, and fruit in their diet. Among those known 

to feed on pollen are Sh. orchidae (Lepschi, 1989), Paratropes 

bilunata (Perry, 1978), Latiblattella lucifrons (Helfer, 

1953), and Ellipsidion sp. (Rentz, 1996). Balta bicolor is 

commonly found on the leaves and spent flower heads of 

Gahnia sp. in eucalypt woodlands (Rentz, 1996) and both 

males and females are attracted to pollen placed on a tree 

branch (Fig. 4.3). In a survey of insects captured by the 

pitcher plant Sarracenia flava in North Carolina, CAN 

(unpubl. data) collected males of four species of Parcoblatta 

(Parc. fulvescens, Parc. uhleriana, Parc. virginica, 

and Parc. lata), and both sexes of Cariblatta lutea. Since 

all these are winged as adults, while females of the Parcoblatta 

species are brachypterous, the cockroaches may 

be seeking nectar as an easily harvested source of energy 

to fuel flight. This suggestion is strengthened by the observation 

that volant Blattella asahinai adults, but not 

nymphs, feed on aphid honeydew (Brenner et al., 1988). 

Trichoblatta sericea in India feeds on the gum exuded 

from the bark of Acacia trees, and less commonly on gum 

from other trees (Azadirachta, Moringa, Enterolobium) 

(Reuben, 1988). Since individuals lived twice as long and 

had four times the reproductive output when fed a diet of 

powdered gum arabic when compared to a diet of biscuit 

crumbs or wheat flour, gum may be providing essential 

nutrients. The digestive physiology of this species would 

be of interest, as most gums are carbohydrate polymers 

that require microbial degradation if they are to be assimilated 

(Adrian, 1976). A number of cockroaches are 

noted as feeding “on flowers” (e.g., Opisthoplatia orientalis—Zhu 

and Tanaka, 2004a; Ectobius pallidus—Payne, 

1973), but it is unclear as to whether the individuals were 

actually feeding on flower petals, or standing on the 

flower ingesting pollen or nectar. Arenivaga apacha (Cohen 

and Cohen, 1976) and possibly other cockroaches 

that dwell in vertebrate burrows feed on the stored seeds 

of their host, while sand-swimming species of Arenivaga 

include the roots of desert shrubs in their diet (Hawke 

and Farley, 1973). Many species feed on ripe fruit, an 

energy-rich, seasonally available food source. Diplotera 

punctata, for example, feeds on mangoes, papayas, and 

oranges, as well as on the outer covering of Acacia pods 

(Bridwell and Swezey, 1915) and the bark of Cypress, Japanese 

cedar, citrus, and Prosopis spp. (Roth, 1979a). 

Leaf Foraging 

In tropical rainforests leaf surfaces are “night habitat” for 

many crepuscular and nocturnal cockroaches. It is the 

only time and place that the majority of cockroaches that 

live in rainforests of Queensland, Australia (D. Rentz, 

pers. comm. to CAN), and Costa Rica (WJB, pers. obs.) 

can be seen. The insects emerge from harborage on the 

forest floor, move up the plants, then out onto foliage, or 

they move onto leaves from the innumerable hiding 

places in the different strata of the forest canopy. Adhesive 

footpads (arolia and euplantae) help the cockroaches 

negotiate sleek planes of vegetation, but it is only young 

leaves that commonly have smooth, simple surfaces. As 

leaves age they become elaborate, textured habitats rich in 

potential food sources (Walter and O’Dowd, 1995) (Fig. 

4.4). In general, leaves provide two menu categories for 

cockroaches (WJB, unpubl. obs.). First, leaves act as serv- 

Fig. 4.3 Balta bicolor feeding on pollen applied to a branch; 

male (left), female (right). Photo courtesy of David Rentz. 

68 COCKROACHES

Fig. 4.4 Beybienkoa sp., night foraging on leaf surface material, Kuranda, Queensland. Photo 

courtesy of David Rentz. 

ing trays for the intercepted rain of particulate organic 

matter that falls perpetually or seasonally from higher 

levels of the forest. This includes bird and other vertebrate 

feces, pollen, spores, leaves, twigs, petioles, sloughed tree 

bark, flower parts, and pieces of ripe fruit originating 

from the plant and from sloppy vertebrate eaters. Also offered 

on these leaf trays are dead leaf material around herbivore 

feeding damage, and the excreta, honeydew, silk 

webbing, eggshells, exuvia, and corpses of other arthropods. 

Live mites, aphids, and other small vulnerable 

arthropods on leaves are potential prey items. The second 

menu category on leaves in tropical forests is the salad 

course: leaves are gardens that support a wide range of 

nonvascular plants (epiphylls) and microbes. These include 

lichens, bryophytes, algae, liverworts, mosses, fungi, 

and bacteria. 

Cockroaches in Costa Rican rainforest have been observed 

feeding on the majority of items listed above (WJB 

and J. Aracena, unpubl. obs.). Dissections of the cockroaches 

and inspection of their gut contents, however, indicate 

that ingestion of the different food types can be 

rather specific. Those cockroaches for which fairly large 

sample sizes are available are listed in Table 4.2. Capucina 

rufa and Cap. patula forage on dead logs, feeding on epiphylls, 

fungi, and bark scraps. Epilampra involucris females 

perch near the ground, where they feed on ground 

litter and the materials that fall onto it. Males of this 

species, which perch on leaves at heights of up to 50 cm, 

eat algae, bryophytes, lichens, pollen, spores, fruit, and 

flakes of shed bark. A subset of small, mobile species fly 

about in the canopy and scrape epiphylls from leaf surfaces 

at night. Imblattella and Cariblatta feed primarily on 

leaf trichomes, blue-green algae, liverworts, and spores. 

Only algae were found in the guts of male, female and juvenile 

Car. imitans. Trichomes, which normally interfere 

with foraging by small herbivores and carnivores (Price, 

2002), are ingested by several cockroach species (WJB, 

unpubl. obs.). The many tropical cockroaches that fulfill 

their nutritional requirements by feeding on the broad 

variety of materials offered on leaf laminae may, like ants 

(Davidson et al., 2003), be categorized as leaf foragers. 

Those that specialize on the epiphylls and other plant 

products (trichomes, pollen, honeydew) found in this 

habitat may be described as cryptic herbivores (Hunt, 

2003). 

Detritus 

Many cockroaches feed on detritus (Roth and Willis, 

1960; Mullins and Cochran, 1987), a broad term applied 

to nonliving matter that originates from a living organism 

(Polis, 1991). A unique feature of detritivores is that 

there is no co-evolutionary relationship between the 

consumer and the ingested substrate. This is in stark contrast 

with the relationship between herbivores and higher 

plants, and in predator-prey systems. A consequence of 

this lack of co-evolutionary interaction is that detritivores 

are less specialized than predators and herbivores, 


and they defy classification into straightforward food 

chains (Anderson, 1983; Price, 2002; Scheu and Setälä, 

2002). The food of detritivores is nutritionally very different 

from feeding on living plants or animals because it 

has been colonized and altered by microbes. Litter is a “resource 

unit” comprised of recently living material, degraded 

litter, dissolved organic matter, complex consortia 

of fungi, bacteria, nematodes, and protozoa, and the 

metabolic products of these (Nalepa et al., 2001a; Scheu 

and Setälä, 2002). The notion that detritivores may ingest 

a large amount of living microbial material, and may develop 

co-evolutionary relationships with these organisms, 

is not typically considered (Chapter 5). 

Dead plant material in varying states of decay is known 

to be the primary food source for cockroach taxa in a variety 

of habitats. This is particularly true for species living 

at or near ground level in tropical forests, which have 

an unlimited supply of decaying litter within easy reach. 

Plant detritus is constantly accumulating on the forest 

floor, either seasonally or constantly. In the rainforest 

canopy, detritivores have access to suspended litter and 

the dead material that typically edges herbivore damage 

on live leaves (Fig. 3.3). Many cockroaches feed on leaf litter 

(Table 4.4), which in general is of higher resource 

quality and decomposes more quickly than twigs and 

other woody materials (Anderson and Swift, 1983); however, 

decayed wood may serve as a food source more commonly 

than is generally appreciated (Table 3.2). In rainforests, 

practically all wood is rotten to some extent, and 

the division between decayed wood, rotted plant litter, 

and soil organic matter is difficult to assess (Collins, 

1989). Many cockroach detritivores live within their food 

source—“a situation reminiscent of paradise”(Scheu and 

Setälä, 2002). 

Physically tough substrates like leaf litter and wood are 

macerated by a combination of mandibular action and 

Table 4.4. Examples of cockroaches subsisting largely on 

leaf litter. 

Habitat Cockroach taxon Reference 

Rainforest Epilampra irmleri Irmler and Furch (1979) 

6 species (Malaysia) Saito (1976) 

20 species of nymphs WJB (pers. obs.) 

(Costa Rica) 

Dry forest, Geoscapheini Rugg and Rose (1991) 

scrub Thorax porcellana Reuben (1988) 

Desert Arenivaga investigata Hawke and Farley (1973) 

Edney et al. (1974) 

Heterogamisca chopardi Grandcolas (1995a) 

Aquatic Litopeltis sp. Seifert and Seifert (1976) 

Poeciloderrhis cribrosa Rocha e Silva Albuquerverticalis 

que et al. (1976) 

Opisthoplatia maculata Takahashi (1926) 

Fig. 4.5 Proventriculus of Blattella germanica, transverse section. 

From Deleporte et al. (1988), courtesy of Daniel Lebrun. 

Scale bar 100 m. When the “teeth” are closed the inward 

pointed denticles almost occlude the lumen. Hairs on the pulvilli 

may help filter the coarse food from the fine (Cornwell, 

1968). 

passage through the proventriculus, a strongly muscled 

and often toothed armature that lies just behind the crop 

(Fig. 4.5). It might be expected that the morphology of 

this organ is functionally related to diet, but that does not 

appear to be the case. The various folds, denticles, and 

pulvilli on the structure are, in fact, useful characters in 

phylogenetic studies of cockroaches (McKittrick, 1964; 

Klass, 1998b). The proventriculus of the wood-feeding 

taxa Cryptocercus (Cryptocercidae) and Panesthia (Blaberidae), 

for example, are completely different; that of 

Cryptocercus resembles that of some termites, and Panesthia 

has the flaccid, wide proventriculus of a blaberid. 

Macropanesthia rhinoceros, which feeds on dead, dry 

leaves, lacks a proventriculus (Day, 1950). This species, as 

well as Geoscapheus dilatatus, Panesthia cribrata, and Cal. 

elegans are known to ingest sand, probably to aid in the 

mechanical fragmentation of their food (Zhang et al., 

1993; Harley Rose, pers. comm. to CAN). 

ANIMAL-BASED FOOD 

Like a large number of herbivores and detritivores (e.g., 

Hoffman and Payne, 1969), many cockroaches incorporate 

animal tissue into their diet when the opportunity 

arises. Parcoblatta uhleriana has been observed feeding 

on mammalian cartilage (Gorton, 1980), but most records 

of cockroaches feeding on living and dead vertebrates 

come from species that dwell in caves (discussed 

below) and from pest cockroaches. The latter can eat a 

great deal of flesh, particularly of human corpses. They 

also nibble on the calluses, wounds, fingernails and toenails, 

eyelashes, eyebrows, earwax, dandruff, eye crust, 

and the nasal mucus of sleeping individuals, particularly 

70 COCKROACHES

children. At times they “bite savagely,” leaving permanent 

scars (Roth and Willis, 1957; Denic et al., 1997). Most reports 

are from ships, nursing homes, unhygienic urban 

settings, and primitive tropical living quarters. See Roth 

and Willis (1957) for a full roster of these horror stories. 

Many cockroaches are equipped for predation: they are 

agile, are aggressive in other contexts, have powerful 

mandibles, and possess spined forelegs to help secure 

prey. The recorded victims of cockroaches include ants, 

parasitic wasps, Polistes larvae, centipedes, dermestids, 

aphids, leafhoppers, mites, and insect eggs (Roth and 

Willis, 1960). Both B. vaga and B. asahinai eat aphids and 

are considered generalist predators (Flock, 1941; Persad 

and Hoy, 2004). Periplaneta americana has been observed 

both catching and eating blowflies in a laboratory setting 

(Cooke, 1968), and pursuing and capturing termite dealates 

in and around dwellings. They pounced on termites 

from a distance of 5 cm, and followed them into crevices 

in the floor (Annandale, 1910; Bowden and Phipps, 

1967). Cockroaches that feed on guano, leaf litter, or epiphylls 

also ingest the invertebrate microfauna that inhabit 

their primary food source (WJB, pers. obs). Dead 

invertebrates are scavenged by Blattella karnyi (Roth 

and Willis, 1954b), Parcoblatta pennsylvanica (Blatchley, 

1920), and P. fuliginosa (Appel and Smith, 2002), among 

others. “The insect collector will often find that cockroaches, 

particularly in the tropics, will play sad havoc 

with his dead specimens” (Froggatt, 1906). 

There are a few instances of cockroaches harvesting the 

secretions and exudates of heterospecific insects. Several 

are known to feed on honeydew (e.g., Eurycotis spp. sipping 

it from fulgorids—Naskrecki, 2005). Parcoblatta 

pennsylvanica has been observed feeding on cercopid 

spittle (Gorton, 1980). Recently two species of Costa Rican 

Macrophyllodromia were observed grazing the white, 

waxy secretion on the tegmina of at least two species of 

Fulgoridae (Fig. 4.6) (Roth and Naskrecki, 2001). 

Conspecifics as Food Sources 

The remaining cases of animal-based food pertain to fellow 

cockroaches. This fits the profile of other detritivores, 

as intraguild predation and cannibalism are widespread 

within decomposer food webs (Scheu and Setälä, 2002). 

There are a few cases of cockroaches preying on other 

cockroach species, like N. cinerea killing and eating D. 

punctata (Roth, 2003a). A more significant source of animal 

tissue, however, originates from same-species interactions 

(Nalepa, 1994). Most records of cockroach cannibalism 

come from domestic pests in lab culture (e.g., 

Periplaneta spp.—Pope, 1953; Roth, 1981a; B. germanica—Gordon, 

1959), and it is the vulnerable that are most 

often taken as prey. Hatchlings, freshly molted nymphs, 

and the weak or wounded are the most frequent victims. 

It is usually the abdomen that is eaten first, to take advantage 

of the uric acid pool stored in the fat body 

(Cochran, 1985). Adult cockroaches in culture (Abbott, 

1926) and in caves (Darlington, 1970) often have their 

wings extensively nibbled (although this may also be the 

result of aggressive interactions). The most ubiquitous 

ecological factor favoring cannibalism is the quality and 

quantity of available food, which depends to varying degrees 

upon population density (Elgar and Crespi, 1992). 

Egg eating is a form of cannibalism, although in some 

cases the ingested eggs may be unfertilized or unviable 

(Joyner and Gould, 1986). In cockroaches, oothecae may 

be partially or entirely eaten prior to hatch (Roth and 

Willis, 1954b; Nalepa, 1988a), and oothecae carried by fe- 

Fig. 4.6 The Costa Rican cockroach Macrophyllodromia maximiliani palpating the elytron of the 

fulgorid Copidocephala guttata. From Roth and Naskrecki (2001), courtesy of Piotr Naskrecki, 

with permission from the Journal of Orthoptera Research. 


Table 4.5. Organic composition of exuvia from adult ecdysis and oothecae from several cockroach 

species, as determined by 13 C-NMR analyses. Reprinted from Kramer et al., “Analysis of cockroach 

oothecae and exuvia by solid state 13 C-NMR spectroscopy,” Insect Biochemistry 21 (1991): pp. 149– 

56; copyright (1991), with permission from Elsevier. 

Relative amount (%) in/on exuvia 

Species Protein Chitin Diphenol Lipid 

Periplaneta americana 49 38 11 2 

Blattella germanica 59 30 9 2 

Gromphadorhina portentosa 53 38 8 1 

Blaberus craniifer 52 42 5 1 

Rhyparobia maderae 61 35 4 1 

Relative amount (%) in/on post-hatch oothecae 

Species Protein Oxalate Diphenol Lipid 

Periplaneta americana 87 8 4 1 

Periplaneta fuliginosa 86 7 6 1 

Blatta orientalis 88 7 4 1 

Blattella germanica 95 1 3 1 

males are not immune to biting and cannibalism by conspecifics 

(Roth and Willis, 1954b; Willis et al., 1958). After 

hatch, neonates of ovoviviparous cockroaches eat the 

embryonic membranes and the oothecal case (Nutting, 

1953b; Willis et al., 1958); the sturdier oothecal cases of 

oviparous species are probably eaten by older nymphs or 

adults. After hatch in Cryptocercus, for example, oothecal 

cases are occasionally found still embedded in wood, but 

chewed flush with the surface of the gallery; hatching 

oothecae isolated from adults always remain intact (Nalepa 

and Mullins, 1992). It is estimated that females of 

Cryptocercus may be able to recover up to 59% of the nitrogen 

invested into a clutch of eggs by consuming the 

oothecal cases after hatch, but it is unknown how much 

of this nitrogen is assimilated (Nalepa and Mullins, 1992). 

Cannibalism may be part of an evolved life history strategy 

in young families of Cryptocercus (Nalepa and Bell, 

1997; Chapter 8). 

Cast skins are a prized food source and are eaten 

quickly by the newly molted nymph or by nearby individuals. 

In P. americana the cast skin is usually consumed 

within an hour after molt (Gould and Deay, 1938), and 

the older the nymph, the more quickly the skin is eaten 

(Nigam, 1932). Nymphs of B. germanica are known to 

force newly emerged individuals away from their cast 

skins and “commence to eat the latter with great gusto” 

(Ross, 1929). A nymph of E. posticus usually eats its exuvium 

immediately after molt, before the new cuticle has 

hardened. Nearby cockroaches also eat fresh exuvia, and 

occasionally the molting cockroach as well (Darlington, 

1970). Competition to feed on exuvia has been observed 

in both Macropanesthia (M. Slaytor, pers. comm. to 

CAN) and Cryptocercus (CAN, unpubl. obs.). In the latter, 

“snatch and run” bouts can occur where an exuvium 

changes ownership a half dozen times or more before it is 

completely consumed. The competition is understandable 

in that a cast skin is a considerable investment on the 

part of a growing nymph; exuvia from young instars of 

E. posticus, for example, comprise nearly 16% of their 

dry weight (Darlington, 1970). The cuticle is made up of 

chains of a polysaccharide, chitin, embedded in a protein 

matrix. Protein and chitin are 17% and 7% nitrogen by 

mass, respectively (Chown and Nicolson, 2004), and together 

these may account for 95% or more of the organic 

materials in an exuvium or oothecal case (Table 4.5). 

Fig. 4.7 Rear view of a male nymph of Periplaneta australasiae, 

showing the proteinaceous secretion that accumulates on the 

cerci and terminal abdominal tergites. Photo courtesy of 

Thomas Eisner. 

72 COCKROACHES

Table 4.6. Conspecifics as food sources (modified from Nalepa, 

1994). 

Feeding behavior 

Selected references 

Cannibalism/necrophagy Gordon (1959), Roth (1981a) 

Oophagy (oothecae/ 

Nutting (1953b), Roth and 

oothecal cases) Willis (1954b), Willis et al. (1958), 

Nalepa (1988a) 

Consumption of exuvia Roth and Willis (1954b), Willis et 

al. (1958) 

Male-female transfer 

Tergal glands 

Nojima et al. (1999b), Kugimiya 

et al. (2003) 

Accessory glands 

Mullins and Keil (1980), Schal 

and Bell (1982) 

Cuticular secretions 

Roth and Stahl (1956), Seelinger 

(from grooming and Seelinger (1983) 

and cercal exudates) 

Parental feeding 

Stay and Coop (1973), Roth 

(1981b), Perry and Nalepa 

(2003) 

Coprophagy Cruden and Markovetz (1984), 

Lembke and Cochran (1990) 

Cockroaches apparently have the enzymes required to 

break down the chitin polysaccharide chain; endogenous 

chitinase is distributed throughout the gut of P. americana 

(Waterhouse and McKellar, 1961). Exuvium consumption 

appears directly related to nitrogen budget in 

P. americana; the behavior occurs more commonly in females, 

in insects reared on a low-protein diet, and in those 

deprived of their fat body endosymbionts (Mira, 2000). 

In addition to the direct consumption of bodies, body 

parts, and reproductive products, cockroaches feed on 

materials exuded from the body of conspecifics in several 

contexts (Table 4.6). A form of nuptial feeding occurs in 

most cockroach species whose mating behaviors have 

been studied. Tergal glands are common in mature male 

cockroaches (Chapter 6). The secretions they produce 

attract the female during courtship, and as she climbs 

onto the male’s back to feed on them she is properly positioned 

for genital contact (Roth, 1969; Brossut and 

Roth, 1977). Tergal secretions are general phagostimulants, 

and gravid, unreceptive females as well as males and 

nymphs feed on the gland of a courting male (Roth and 

Willis, 1952a; LMR, unpubl. obs.; Nojima et al., 1999b). 

In at least two blattellid species, B. germanica and X. hamata, 

males use the secretion of the uricose (accessory) 

gland as a nuptial gift (Mullins and Keil, 1980; Schal and 

Bell, 1982). During auto- and allogrooming cockroaches 

may ingest cuticular waxes, as well as anything else on the 

body surface; they spend a significant amount of time 

grooming antennae, legs, feet, and wings (Bell, 1990). Females 

and nymphs of both sexes in a variety of oviparous 

species produce a grayish viscous secretion on the cerci 

and terminal abdominal segments (Fig. 4.7). The material 

reappears 5–10 min after molt or the removal of the 

secretion. During autogrooming of the glandular area, 

the upper layer of the secretion is removed by the hind 

tibia; the leg is then cleaned by drawing it through the 

mouthparts (Naylor, 1964). The material is primarily 

(90%) proteinaceous and may serve as supplemental food 

(Roth and Stahl, 1956). Nymphs have been observed ingesting 

it from each other (D. Abed and R. Brossut, pers. 

comm. to CAN). Newly molted cockroaches eat their exuvium 

together with the glandular material accumulated 

on it (Roth and Stahl, 1956). The secretion also serves 

in defense, by mechanically impairing small predatory 

arthropods (Roth and Alsop, 1978; Ichinosé and Zennyoji, 

1980). Allogrooming has been observed in Pane. cribrata 

(Rugg, 1987) and Cryptocercus punctulatus (Seelinger 

and Seelinger, 1983), neither of which produce this 

type of exudate. Neonates in at least six cockroach subfamilies 

feed on body fluids or glandular secretions of the 

mother (Chapter 8). These originate from a variety of locations 

on the adult body and have been analyzed only in 

the viviparous Diploptera punctata (Chapter 7). 

CAVES 

Caves are almost entirely heterotrophic; they depend on 

the transfer of energy and nutrients from the surface environment. 

Food is brought in with plant roots, water 

(i.e., organic material brought in with percolating rainwater, 

flooding, streams), and animals, particularly those 

that feed in the outside environment but return to the 

cave for shelter during their inactive period (Howarth, 

1983; Gnaspini and Trajano, 2000; Hüppop, 2000). Although 

caves are generally considered food deficient, 

there is tremendous variation among and within caves. 

Food scarcity may be considered general, periodic (variation 

in time), or patchy (variation in space) (Hüppop, 

2000). The best examples of the latter are guano beds that 

can be several meters deep and support tremendous populations 

of invertebrates. These islands of life, however, 

“are surrounded by desert, as most of the underground 

space is severely oligotrophic and sparsely populated” 

(Gilbert and Deharveng, 2002). 

Guano 

Vertebrate excrement is by far the most important nutritional 

base for cave Blattaria; cockroaches that feed 

on guano are apparently found on all main continents 

(Gnaspini and Trajano, 2000). If the vertebrates use the 

same roosting areas year round, then guano deposition is 


predictable in space as well as time and can support very 

large, persistent groups of cockroaches (guanobies). This 

occurs primarily in the tropics, because there food is 

available for bats throughout the year (Poulson and 

Lavoie, 2000). Cave cockroaches feed on the droppings of 

birds and of frugivorous, insectivorous, and haematophagous 

bats, but not carnivorous bats (Table 13.1 in 

Gnaspini and Trajano, 2000). The abundance and quality 

of guano varies not only in relation to the diet of a vertebrate 

guano source, but also seasonally, depending on 

roosting sites and the availability of food items (Darlington, 

1995a). Communities that develop on guano can be 

very distinct. In one Australian cave, guano may be inhabited 

by mites, pseudoscorpions, beetles, and maggots, 

while in a nearby cave the guano is dominated by cockroaches 

(Paratemnopteryx sp.) and isopods (Howarth, 

1988). Eublaberus distanti living in Tamana Cave, Trinidad, 

wait nightly buried under the surface of guano, with 

their antennae extended above the surface. When the insectivorous 

bat Natalus tumidirostris begins to return 

from foraging at about 3:00 a.m., the cockroaches emerge 

to feed on the fresh droppings raining from above. The 

frugivorous bat Phyllostomus hastatus hastatus is found in 

the same cave, and though Eub. distanti may burrow 

through their droppings, the cockroaches do not feed on 

them (Hill, 1981). None of the six cockroach species 

found in the caves of the Nullarbor Plain in south Australia 

are associated with bat guano, but Paratemnopteryx 

rufa and Trogloblattella nullarborensis utilize bird droppings 

(Richards, 1971). 

Most cockroaches that live on the surface of guano appear 

highly polyphagous (Richards, 1971) and will take 

advantage of any animal or vegetable matter present in 

the habitat. Indeed, species able to benefit from all types 

of food present in caves have more aptitude for colonizing 

the subterranean environment (Vandel, 1965). The 

gut contents of Eub. posticus are indistinguishable from 

guano, but Darlington (1970, 1995a) considers both Eub. 

distanti and Eub. posticus primarily as scavengers on the 

guano surface. These cockroaches are not indiscriminant 

feeders, however, as they will pick out the energy-rich 

parts of food presented to them (Darlington, 1970). The 

cave floor in Guanapo is covered with bat droppings, dead 

bats, live and dead invertebrates, as well as fruit pulp, 

seeds, nuts, and other vegetable fragments defecated by 

the bats (Darlington, 1995–1996). In cave passages remote 

from guano beds the choices are much more restricted. 

Leaves, twigs, and soil that wash or fall into caves 

generally form the food base for troglobites (Poulson and 

White, 1969). There also may be occasional bonanzas of 

small mammals that blunder into caves but cannot survive 

there (Krajick, 2001). The ability of many cockroaches 

to endure long intervals without food, particularly 

if water is available (Table 4.3), may allow for exploitation 

of the deep cave environment. This starvation 

resistance is based at least in part on the capacity to binge 

at a single meal when food is available, together with the 

bacteroid-assisted ability to mete out stored reserves from 

the fat body when times are lean. 

Plant Food in Caves 

Cavernicolous cockroaches that depend on plant litter 

transported by water (Roth and McGavin, 1994; Weinstein, 

1994) are attracted to traps baited with wet leaves 

(Slaney and Weinstein, 1996). While sinking streams may 

be continual, low-level sources of flotsam, seasonal flood 

debris supplies the bulk of the plant litter in most tropical 

caves (Howarth, 1983; Gnaspini and Trajano, 2000). 

In Australia, some caves may receive an influx of water 

and associated organic matter only once every 5 yr 

(Humphreys, 1993). Seeds defecated by frugivorous bats 

and the seeds of palm and other plants regurgitated by 

oilbirds commonly sprout in guano beds (Darlington, 

1995b). The “forests of etiolated seedlings” (Poulson and 

Lavoie, 2000) that emerge may serve as food to cave cockroaches, 

but this is unconfirmed. Periplaneta, Blaberus, 

and other genera that feed on the guano of frugivorous 

bats also take advantage of fruit pieces dropped onto the 

floor (e.g., Gautier, 1974a). Fruit bats in Trinidad bring 

the fruit back to the caves, eat part of it, and then drop the 

remainder (Brossut, 1983, p. 150). 

Live/Dead Vertebrates as Food in Caves 

Those cockroaches that live in bat guano opportunistically 

feed on live, dead, and decomposing bats. Juveniles 

in maternity roosts that lose their grip and fall to the 

cave floor are particularly vulnerable (Darlington, 1970). 

Blaberus sp. have been observed rending the flesh of a 

freshly fallen bat, starting with the eyes and lips (D.W., 

1984). Among the species recorded as feeding on dead 

bats are Blattella cavernicola (Roth, 1985), Gyna caffrorum, 

Gyna sp., Hebardina spp., Symploce incuriosa 

(Braack, 1989), and Pycnoscelus indicus (Roth, 1980). 

Cockroaches that live in the guano of oilbirds are treated 

to fallen eggs and occasional bird corpses (Darlington, 

1995b). LMR once placed a dead mouse into a large 

culture of Blaberus dytiscoides and it was skeletonized 

overnight; he suggested to his museum colleagues that the 

cockroaches might be used to clean vertebrate skeletons. 

Live/Dead Invertebrates as Food in Caves 

Many cave cockroaches scavenge dead and injured invertebrates 

including conspecifics, and several have been re- 

74 COCKROACHES

ported to take live victims. Both B. cavernicola (Roth, 

1985) and Pyc. indicus (Roth, 1980) prey on the larvae of 

tinead moths; Pyc. indicus also appears to be the main 

predator of a hairy earwig (Arixenia esau) found on the 

guano heap. Crop contents of both Trog. nullarborensis 

and Para. rufa consisted of numerous small chitinous 

particles and setae. In Trog. nullarborensis it was possible 

to identify small dipterous wing fragments and lepidopterous 

scales (Richards, 1971). 

Geophagy in Caves 

True troglobites are rarely associated with guano but little 

information is available regarding their food sources. 

At least two cockroach species appear geophagous. Roth 

(1988) found clay in the guts of five nymphs of Nocticola 

australiensis, and suggested that Neotrogloblattella chapmani 

subsists on the same diet (Roth, 1980). The latter is 

confined to remote passages away from guano beds. Clays 

and silts in caves contain organic material, protists, nematodes, 

and numerous bacteria that can serve as food 

for cavernicoles. Chemoautotrophic bacteria may be particularly 

important in that they are able to synthesize vitamins 

(Vandel, 1965). Cave clay is a source of nutrition 

in a number of cave animals, including amphipods, beetles, 

and salamanders (Barr, 1968). One species of Onychiurus 

(Collembola) survived over 2 yr on cave clay 

alone (Christiansen, 1970). 

Microbivory in Caves 

As with detritivores in the epigean environment, the primary 

food of cave cockroaches may be the decay organisms, 

rather than the organic matter itself (Darlington, 

1970). This may be particularly true for cockroaches that 

spend their juvenile period or their entire lives buried in 

guano. In Sim. conserfarium, for example, groups of all 

ages are found at a depth of 5–30 cm in the guano of fruit 

bats in West African caves (Roth and Naskrecki, 2003). 

What better microbial incubator than a pile of feces, leaf 

litter, or organic soil in a dark, humid environment in the 

tropics? In addition to ingesting microbial cytoplasm and 

small microbivores together with various decomposing 

substrates, it is possible that some cave cockroaches directly 

graze thick beds of bacteria and fungi that live off 

the very rocks. These include stalactite-like drips of 

massed bacteria, and thick slimes on walls (Krajick, 

2001). In Tamana cave, fungi dominate the guano of insectivorous 

bats. The low pH combined with bacteriocides 

produced by the fungi is responsible for the low 

number and diversity of bacteria. The pH of frugivorous 

bat guano, on the other hand, favors bacterial growth, 

which supports a dense population of nematodes (Hill, 

1981). Recent surveys using molecular techniques indicate 

that even oligotrophic caves support a rich bacterial 

community able to subsist on trace organics or the fixation 

of atmospheric gases (Barton et al., 2004). 


FIVE 

Microbes: 

The Unseen Influence 

on the 

back of a cockroach 

no larger than 

myself millions of 

influenza germs may lodge i 

have a sense of responsibility 

to the public and i 

have been lying for two weeks 

in a barrel of moth 

balls in a drug store 

without food or water 

—archy, “quarantined” 

Why are cockroaches almost universally loathed? One of the primary reasons is because 

of the habitats they frequent in the human environment. Cockroaches are associated with 

sewers, cesspools, latrines, septic tanks, garbage cans, chicken houses, animal cages, and 

anywhere else there are biological waste products. Their attraction to human and animal 

feces, rotting food, secretions from corpses, sputum, pus, and the like gives them a well 

earned “disgust factor” among the general public (Roth and Willis, 1957). Why, however, 

are they are attracted to environments reviled by most other animals? It is it is obvious 

to us that the common denominator in all these moist, organic habitats is the staggeringly 

dominant presence of bacteria, protozoa, amoebae, fungi, and other microbial material.While 

these consortia are rarely if ever discussed as food for macroarthropods (e.g., 

Coll and Guershon 2002), in the case of cockroaches, that may be a glaring oversight. The 

main source of nourishment for cockroaches in mines and sewers, for example, is human 

feces (see Roth and Willis, 1957, plate 4), which can be 80% bacterial, by fresh weight 

(Draser and Barrow, 1985). Blattella germanica has been observed feeding on mouth secretions 

of corpses riddled with lung disease; these secretions contained infectious bacteria 

in almost pure culture (Roth and Willis, 1957). Granted, the above cases refer to 

cockroaches associated with the man-made environment, while the main focus of this 

book is on the 99% species that live in the wild. We contend, however, that microbes 

are an essential influence in the nutrition, ecology, and evolution of all cockroaches; indeed, 

it can be difficult to determine the organismal boundaries between them. Here we 

address microbes as gut and fat body mutualists, as part of the external rumen, the food 

value of microbes, various mechanisms by which cockroaches may ingest them, and 

some non-nutritional microbial influences. Finally, we discuss some strategies used by 

cockroaches to evade and manage disease in their microbe-saturated habitats. 

76

MICROBES IN AND ON FOODSTUFFS 

Because of the intimate association of microbial consortia 

and the substrate they are decomposing, both are ingested 

by detritivores. It is the microbial material, rather 

than the substrate that may serve as the primary source of 

nutrients (Berrie, 1975; Plante et al., 1990; Anduaga and 

Halffter, 1993; Gray and Boucot, 1993; Scheu and Setälä, 

2002). Scanning electron micrographs show that millipedes, 

for example, strip bacteria from the surface of 

ingested leaf litter (Bignell, 1989), and similar to cockroaches, 

they can be found feeding on corpses in advanced 

stages of decay (Hoffman and Payne, 1969). Most 

foods known to be included in the diet of cockroaches in 

natural habitats are profusely covered with microbes. 

Bacteria and fungi are present on leaves before they are 

abscised, and their numbers increase rapidly as soon as 

the litter has been wetted on the ground (Archibold, 

1995). The floor of a tropical rainforest is saturated with 

microbial decomposers, and as decay is successional, different 

species of microbe are associated with different 

parts of the process. A square meter of a tropical forest 

floor may contain leaves from 50 or more plant species, 

and each leaf type may have a different microflora and 

microfauna. Microbial populations may also vary with 

season, with climate, with soil, and with the structure of 

the forest; there is no simple way to recognize all of the 

variables (Stout, 1974). Dead logs, treeholes, bird and rodent 

nests, bat caves, and other such cockroach habitats 

are also microbial incubators. Bacteria are ubiquitous, 

but flagellates, small amoebae, and ciliates are also important 

agents of decomposition, and are associated with 

every stage of plant growth and decline, from the phylloplane 

to rhizosphere (Stout, 1974). Fermenting fruits and 

plant exudates (e.g., oozing sap) support the growth of 

yeasts, which are exploited as a source of nutrients in 

many insect species (Kukor and Martin, 1986). Cockroaches 

in culture favor overripe fruit, with the rotted 

part of the fruit eaten first, and fruit fragments intercepted 

by leaves in tropical forests are far from fresh. Blattella 

vaga has been observed in large numbers around decaying 

dates on the ground (Roth, 1985). Vertebrate feces 

are obviously rich sources of microbial biomass, particularly 

in bat caves, and, as discussed in Chapter 4, some 

cave cockroaches apparently assimilate bacteria from ingested 

soil. 

THE ROLE OF MICROBES IN DIGESTION 

The success of cockroaches within their nutritional environment 

results in large part from their relationship with 

microorganisms (Mullins and Cochran, 1987) at three 

levels: the microbes that comprise the gut fauna, the microbes 

found on ingested foodstuffs and fecal pellets, and 

the intracellular bacteria in the fat body. 

Hindgut Microbes 

The guts of all cockroach species examined house a diverse 

anaerobic microbiota, with ciliates, amoebae, flagellates, 

and a heterogeneous prokaryotic assemblage, 

including spirochetes (Kidder, 1937; Steinhaus, 1946; 

Guthrie and Tindall, 1968; Bracke et al., 1979; Bignell, 

1981; Cruden and Markovetz, 1984; Sanchez et al., 1994; 

Zurek and Keddie, 1996; Lilburn et al., 2001). Methanogenic 

bacteria, a good indicator of microbial fermentative 

activity (Cazemier et al., 1997b), are found both free in 

the gut lumen and in symbiotic association with ciliates 

and mastigotes in most cockroach species tested (Bracke 

et al., 1979; Gijzen and Barugahare, 1992; Hackstein and 

Strumm, 1994). Nyctotherus (Fig. 5.1) can host more than 

4000 methanogens per cell (Hackstein and Strumm, 

1994), and hundreds to thousands of the ciliate can be 

found in full-grown cockroaches (van Hoek et al., 1998). 

Microbes are densely packed within the gut, but in a predictable 

spatial arrangement; food is processed sequentially 

by specific microbial groups as it makes its way 

through the digestive system. Volatile fatty acids (VFAs) 

are present in the hindgut, further suggesting the degradation 

of cellulose and other plant polysaccharides 

(Bracke and Markovetz, 1980). The hindgut wall of cockroaches 

is permeable to organic acids (Bignell, 1980; 

Bracke and Markovetz, 1980; Maddrell and Gardiner, 

1980), indicating that the host may directly benefit from 

the products of microbial fermentation. Long cuticular 

spines and extensive infolding of the hindgut wall increase 

surface area and provide points of attachment for 

the microbes (Bignell, 1980; Cruden and Markovetz, 

1987; Cazemier et al., 1997a). Finally, redox potentials indicate 

conditions are more reducing than in other insect 

species, with the exception of termites (Bignell, 1984). 

These features of cockroach digestive physiology support 

the notion that plant structural polymers play a significant 

role in the nutritional ecology of Blattaria; however, 

we currently lack enough information to appreciate 

fully the subtleties of the interactions in the hindgut. It is 

known to be a fairly open system, with a core group of 

mutualists, together with a “floating”pool of microbes recruited 

from those entering with food material (Bignell, 

1977b, pers. comm. to CAN). Populations of the microbial 

community shift dynamically in relation to the food 

choices of the host.Whatever rotting substrate is ingested, 

a suite of microbes responds and proliferates (Gijzen et 

al., 1991, 1994; Kane and Breznak, 1991; Zurek and Keddie, 

1998; Feinberg et al., 1999). 

Cellulases are distributed throughout the cockroach 

MICROBES: THE UNSEEN INFLUENCE 77

ingested because they serve as fuel for microbial growth 

on the ingested substrate, on feces, and in the gut, and it 

is the microbes and their products that are of primary nutritive 

importance to the cockroach (Nalepa et al., 2001a). 

Fig 5.1 Scanning electron micrograph of the ciliate Nyctotherus 

ovalis from the hindgut of Periplaneta americana. Scale 

bar 20 m. From van Hoek et al. (1998); photo courtesy of 

J. Hackstein, with permission of the journal Molecular Biology 

and Evolution. 

digestive system, and these enzymes are both endogenous 

and microbial in origin (Wharton and Wharton, 1965; 

Wharton et al., 1965; Bignell, 1977a; Cruden and Markovetz, 

1979; Gijzen et al., 1994; Scrivener and Slaytor, 

1994b). The nature of the contribution of cellulose to 

cockroach nutritional ecology, however, has been difficult 

to determine; in most cases no obvious nutritional benefit 

can be detected (Bignell, 1976, 1978), even in some 

wood-feeding cockroaches. Zhang et al. (1993), for example, 

found that Geoscapheus dilatatus, which feeds on 

dead, dry leaves, was able to utilize cellulose and hemicellulose 

more efficiently than the wood-feeding species 

Panesthia cribrata. The latter was surprisingly inefficient 

in extracting both cellulose (15%) and hemicellulose 

(3%) from its diet. In omnivorous domestic species, cellulose 

digestion may be a backup strategy, to be used 

when other available foods are inadequate (Jones and 

Raubenheimer, 2001). This is supported by evidence that 

solids are retained longer in the gut of starving Periplaneta 

americana (Bignell, 1981), allowing more time for 

processing the less digestible components. Retention time 

in animals with hindgut fermentation is directly related 

to digestive assimilation and efficiency (Dow, 1986; van 

Soest, 1994). The fact that so many cockroaches feed on 

cellulose-based substrates in the field but there is so little 

evidence for it playing a significant metabolic role suggests 

another possible function: the breakdown of cellulose 

may primarily provide energy for bacterial metabolism 

(Slaytor, 1992, 2000). Fibrous materials, then, may be 

Ontogeny of Microbial Dependence 

Although it is often tacitly assumed that hosts derive net 

advantage from their mutualists throughout their lifecycle, 

in a number of associations it is only at key stages 

in the host lifecycle that exploitation of symbionts is important 

(Smith, 1992; Bronstein, 1994). Regardless of the 

exact nature of the benefits, young cockroaches depend 

more than older stages on gut microbiota. If the hindgut 

anaerobic community is eliminated, adequately fed 

adults are not affected. The overall growth of juvenile 

hosts, however, is impeded, and results in extended developmental 

periods. The weight of antibiotic-treated P. 

americana differed by 33% from controls at 60 days of 

age. Defaunation also lowered methane production and 

VFA concentrations within the hindgut, and the gut itself 

became atrophied (Bracke et al., 1978; Cruden and 

Markovetz, 1987; Gijzen and Barugahare, 1992; Zurek 

and Keddie, 1996). 

The nutritional requisites of young cockroaches also 

differ from those of adults (P. americana), and are reflected 

in the activities of hindgut anaerobic bacteria, including 

methanogens (Kane and Breznak, 1991; Gijzen 

and Barugahare, 1992; Zurek and Keddie, 1996). Juvenile 

P. americana produce significantly more methane than 

adults, particularly when on high-fiber diets (Kane and 

Breznak, 1991), and demonstrable differences occur in 

the proportions of VFAs in the guts of adults versus juvenile 

stages (Blaberus discoidalis) fed on the same dog food 

diet (McFarlane and Alli, 1985). 

Coprophagy 

Although coprophagy simply means feeding on fecal material, 

it is an extremely complex, multifactorial behavior 

(Ullrich et al., 1992; Nalepa et al., 2001a). Fecal ingestion 

can be subdivided into several broadly overlapping categories, 

depending on the identity of the depositor, the nature 

of the fecal material, the developmental stage of the 

coprophage, and the degree to which feces are a mainstay 

of the diet. Many cockroaches feed on the feces of vertebrates, 

such as Periplaneta spp. in sewers or caves, desert 

cockroaches attracted to bovine and equine dung 

(Schoenly, 1983), and a variety of species attracted to bird 

droppings (Fig. 5.2). Here we highlight the feces of invertebrate 

detritivores (including conspecifics) as a source of 

cockroach food, and divide the behavior into three, not 

mutually exclusive categories. 

78 COCKROACHES

Fig. 5.2 Unidentified nymph feeding on bird excrement, Ecuador. 

Photo courtesy of Edward S. Ross. 

Fig. 5.3 Detritivore-microbial interactions during coprophagy. 

When a cockroach feeds on a refractory food item (A), any 

starches, sugars, lipids present are digested, and endogenous 

cellulases permit at least some structural polysaccharides to be 

degraded as well. Much of the masticated litter, however, may 

be excreted relatively unchanged (B), and serve as substrate for 

microbial growth (C). Ingested microbes, whether from the 

substrate (D) or from the fecal pellets of conspecifics (C), may 

be digested, passed in the feces, or selectively retained as mutualists. 

Microbes on the food item, on the feces, and in the 

hindgut are sources of metabolites and exoenzymes of possible 

benefit to the insect (E). Metabolites of the insect and of the 

gut fauna excreted with the feces (F) may be used by microbes 

colonizing the pellets or reingested by the host during coprophagy. 

Various authors shift the balance among these components, 

depending on the arthropod, its diet, its environment, 

and its age. From Nalepa et al. (2001a), with the permission of 

Birkhäuser Verlag. 

Coprophagy as a Source of Microbial Protein 

and Metabolites 

As food, the feces of detritivores are not fundamentally 

different from rotting organic matter; the feces of many 

differ very little from the parent plant tissue (Webb, 1976; 

Stevenson and Dindal, 1987; Labandeira et al., 1997). The 

differences that do occur, however, are important ones: 

feces are higher in pH, have a greater capacity to retain 

moisture, have increased surface to volume ratios, and 

generally occur in a form more suitable for microbial 

growth (McBrayer, 1973). Fecal pellets are colonized by a 

succession of microbes immediately after gut transit, with 

microflora increasing up to 100-fold (Lodha, 1974; Anderson 

and Bignell, 1980; Bignell, 1989). Fragmentation 

of litter is particularly important for bacterial growth, for 

unlike fungi, whose hyphae can penetrate tissues, bacterial 

growth is largely confined to surfaces (Dix and 

Webster, 1995; Reddy, 1995). The process is similar to gardeners 

creating a compost pile: microbially mediated decomposition 

occurs best when plant litter is moist and 

routinely turned. Coprophagy exploits the microbial 

consortia concentrated on these recycled cellulose-based 

foodstuffs (Fig. 5.3); the microorganisms serve not only 

as a source of nutrients and gut mutualists, but they also 

“predigest” recalcitrant substrates. Microbial dominance 

is so pronounced that fecal pellets may be considered living 

organisms. They consist largely of living cells, they 

consume and release nutrients and organic matter, and 

they serve as food for animals higher on the food chain 

(Johannes and Satomi, 1966). 

Coprophagy as a Mechanism for Passing 

Hindgut Mutualists 

All developmental stages feed on feces, but coprophagy is 

most prevalent in the early instars of gregarious domestic 

cockroaches (B. germanica, P. americana, P. fuliginosa) 

(Shimamura et al., 1994; Wang et al., 1995; Kopanic et al., 

2001). Feces contain protozoan cysts, bacterial cells, and 

spores, and are the primary source of inoculative microbes 

(Hoyte, 1961a; Cruden and Markovetz, 1984). 

Very young cockroaches, with a hindgut volume of 1 l, 

already show significant bacterial activity (Cazemier et 

al., 1997a). Repeated ingestion of feces is no doubt required, 

however, because a successional colonization of 

the various gut niches by microbes is the norm (Savage, 

1977). Obligate anaerobes have to be preceded by facultative 

anaerobes, and a complex bacterial community has 

to precede protozoan populations (Atlas and Bartha, 

1998). Because cockroach aggregations are generally species 

specific, horizontal transmission of microbial mutualists 

from contemporary conspecifics may be considered 

typical. Mixed-species aggregations are occasionally re- 


ported (Roth and Willis, 1960). Neonates, then, may also 

have sporadic access to interspecific fecal material. Analysis 

of rDNA repeats from the cockroach hindgut ciliate 

Nyctotherus indicates that there is a significant phylogenetic 

component to the distribution of the ciliates among 

hosts, but transpecific shifts do occur (van Hoek et al., 

1998). The longevity of cysts and spores in fecal pellets 

would contribute to transmission across species; cysts of 

Nyctotherus are estimated to survive 20 weeks under favorable 

conditions (Hoyte, 1961b). 

We have little information on transmission of gut mutualists 

in non-gregarious species. In subsocial species of 

cockroaches or those with a short period of female 

brooding, transmission is probably vertical, via filial coprophagy 

(Nalepa et al., 2001a). In Cryptocercus spp. intergenerational 

transfer occurs via proctodeal trophallaxis 

(Seelinger and Seelinger, 1983; Nalepa, 1984), the 

direct transfer of hindgut fluids from the rectal pouch of 

a donor to the mouth of a receiver (McMahan, 1969). We 

do not know the mechanism of microbial transmission in 

oviparous species that abandon the egg case. Perhaps the 

female defecates in the vicinity of the ootheca, or the eggs 

are preferentially deposited near conspecific feces. Alternatively, 

neonates may acquire their gut biota directly 

from ingested detritus. Metabolically complementary consortia 

of microbes are always present on ingested organic 

material, because the microorganisms are themselves using 

it as a food source (Costerton, 1992; Shapiro, 1997). 

The mode of transmission of gut microbes in cockroaches 

is related to the degree of host-microbe interdependence 

and to host social behaviors; these three comprise 

a co-varying character suite (Troyer, 1984; Ewald, 

1987; Nalepa, 1991; Chapter 9). 

Coprophagy as a Mechanism for Passing 

Cockroach-Derived Substances 

A coprophage has access to the metabolites, soluble nutrients, 

exoenzymes, and waste products of microbes 

both proliferating on feces and housed in the host digestive 

system, but also to products that originate from the 

insect host itself. The excretion of urate-containing fecal 

pellets by some blattellids can be a mode of intraspecific 

nitrogen transfer (Cochran, 1986b; Lembke and Cochran, 

1990), discussed below. There are behaviorally distinct 

defecation behaviors in P. americana associated with 

physically different feces, and certain types of feces are 

eaten by early instars more frequently than others. Young 

nymphs were the only developmental stage observed 

feeding on the more liquid feces smeared on the substrate 

(Deleporte, 1988). Adult Cryptocercus punctulatus occasionally 

produce a fecal pellet that provokes a feeding 

frenzy in their offspring, while other pellets are nibbled or 

ignored (Fig. 5.4) (Nalepa, 1994). This behavior was also 

Fig. 5.4 First instars of Cryptocercus punctulatus massed on 

and competing for a fecal pellet recently excreted by the adult 

female. Only certain pellets induce this behavior. Photo by C.A. 

Nalepa. 

noted in C. kyebangensis as “clumping behavior” (Park et 

al., 2002). The basis of the appeal of these pellets is unknown. 

MICROBES AS DIRECT FOOD SOURCES 

It is extremely difficult to characterize the degree to which 

microbes are used as food. Ingested microbes may be digested, 

take up temporary residence, or pass through; 

many live as commensals and symbionts. Studies of cockroaches 

as disease vectors indicate that some bacteria fed 

to cockroaches are passed with feces, while others could 

not be recovered even if billions were repeatedly ingested 

(Roth and Willis, 1957). A mushroom certainly qualifies 

as food, but so does any microbe that dies within the digestive 

system, releasing its nutrients to be assimilated by 

the cockroach host, other microbes resident in the gut, or 

a coprophage feeding on a subsequent fecal pellet. We do 

not know the degree to which cockroaches feeding on 

dead plant material handle the substrate/microbe package 

in bulk (the gourmand strategy) versus pick through 

the detrital community, ingesting only the relatively rich 

microbial biomass (the gourmet strategy). If the latter, 

they are not detritivores, because they feed primarily on 

living matter and on material of high food value (Plante 

et al., 1990). The gourmet strategy may be common 

among the youngest cockroach nymphs in tropical rainforests. 

Many of them never leave the leaf litter (WJB, 

pers. obs.), and small browsers can be highly selective 

80 COCKROACHES

(Sibley, 1981). Even if a cockroach is a gourmand, however, 

it may only digest and assimilate the microbial biomass, 

and pass the substrate in feces relatively unchanged, 

“like feeding on peanut butter spread on an indigestible 

biscuit” (Cummins, 1974). 

Regardless of the strategy, it is generally agreed that for 

most detritivores microorganisms are the major, if not 

sole source of proteinaceous food, and are assimilated 

with high efficiency, 90% or more in the case of bacteria 

(White, 1985, 1993; Bignell, 1989; Plante et al., 1990). On 

a dry weight basis, fungi are 2–8% nitrogen, yeasts are 

7.5–8.5%, and bacteria are 11.5–12.5% (Table 5.1). 

These levels are comparable to arthropod tissue and may 

exceed cockroach tissue (about 9.5% in C. punctulatus 

adults) (Nalepa and Mullins, 1992). In addition to being 

rich sources of nitrogen, microbes contain high levels of 

macronutrients such as lipids and carbohydrates, and 

critical micronutrients, such as unsaturated fatty acids, 

sterols, and vitamins (Martin and Kukor, 1984). Even if 

the ingested biomass is small, the nutrient value may be 

highly significant (Seastedt, 1984; Ullrich et al., 1992). 

Irmler and Furch (1979), for example, pointed out that a 

litter-feeding cockroach in Amazonia would need to consume 

impossible amounts (30–40 times its energy requirement) 

of litter to satisfy its phosphorus requirement; 

it is known, however, that microbial tissue is a rich 

source of this element (Swift et al., 1979). 

The External Rumen 

The importance of microbial tissue to an arthropod may 

reside as much in its metabolic characteristics while on 

Table 5.1. Nitrogen levels of various natural materials exploited 

as food by invertebrates. Compiled by Martin and Kukor (1984). 

Material 

Nitrogen content 

(% dry weight) 

Bacteria 11.5–12.5 

Algae 7.5–10 

Yeast 7.5–8.5 

Arthropod tissue 6.2–14.0 

Filamentous fungi 2.0–8.0 

Pollen 2.0–7.0 

Seeds 1.0–7.0 

Cambium 0.9–5.0 

Live foliage 0.7–5.0 

Leaf litter 0.5–2.5 

Soil 0.1–1.1 

Wood 0.03–0.2 

Phloem sap 0.004–0.6 

Xylem sap 0.0002–0.1 

recalcitrant substrates as in its nutrient content once ingested. 

The bacteria and fungi responsible for decay 

predigest plant litter in a phenomenon known as the “external 

rumen.” The microbes remove or detoxify unpalatable 

chemicals (e.g., tannins, phenols, terpenes), release 

carbon sources for assimilation, and physically soften the 

substrate. These changes improve the palatability of plant 

litter and increase both its water-holding capacity and its 

nutritional value (Wallwork, 1976; Eaton and Hale, 1993; 

Scrivener and Slaytor, 1994a; Dix and Webster, 1995). As 

a result, decay organisms can guide food choice in cockroaches. 

Both Cryptocercus and Panesthiinae are collected 

from a wide variety of host log taxa, as long as the logs are 

permeated with brown rot fungi (Mamaev, 1973; Nalepa, 

2003). It is the physical softening of wood that was suggested 

as the primary fungal-associated benefit for Pane. 

cribrata by Scrivener and Slaytor (1994a). Ingested fungal 

enzymes did not contribute to cellulose digestion, and 

fungal-produced sugars were not a significant source of 

carbohydrate. Microbial softening of plant litter may be 

particularly important for juveniles (Nalepa, 1994). Physically 

hard food is known to affect cockroach development 

(Cooper and Schal, 1992) and young cockroach 

nymphs preferentially feed on the softer parts of decaying 

leaves on the forest floor (WJB, pers. obs.) 

Microbes on the Body 

Omnivores and detritivores contact microbes at much 

higher rates than do herbivores or carnivores (Draser and 

Barrow, 1985). In cockroaches, a high frequency of encounter 

is obvious from the habitats they frequent and 

from the abundant literature on their role as vectors. A 

large number and variety of bacteria, parasites, and fungi 

are carried passively on the cuticle of pest cockroaches 

(Roth and Willis, 1957; Fotedar et al., 1991; Rivault et al., 

1993). Despite being nonfastidious feeders with regard to 

bacteria, however, cockroaches are scrupulous in keeping 

their external surfaces clean (Fig. 5.5). More than 50% of 

their time may be spent grooming (Bell, 1990) and in 

many species the legs are morphologically modified with 

comb-like tubercles, spines, or hairs to aid the process 

(Mackerras, 1967b; Arnold, 1974). Mackerras (1965a) described 

the concentration of hairs on the ventral surfaces 

of the fore and hind tibiae of Polyzosteria spp. as “long 

handled clothes brushes” used to sweep both dorsal and 

ventral surfaces of the abdomen. The final stage of the 

grooming process is to bring the leg forward to be 

cleansed by the mouthparts (Fig. 1.18). It seems reasonable 

to assume that microbes and other particulate matter 

concentrated on the legs during grooming activities 

are ingested at this point and may be used as food. This 

suggestion is strengthened by studies of the wood-feed- 


ing cockroach Cryptocercus. An average of 234 microbial 

colony-forming units/cm 2 cuticle have been detected on 

C. punctulatus (Rosengaus et al., 2003), and the insects are 

known to allogroom, using their mouthparts to directly 

graze the cuticular surface of conspecifics.Young nymphs 

spend 8% of their time in mutual grooming (Fig. 5.5B) 

and 15–20% of their time grooming adults. Grooming 

decreases with increasing age, and allogrooming was 

never observed in adults (Seelinger and Seelinger, 1983). 

Grooming has a number of important functions, and 

high levels of autogrooming may be related primarily 

to the prevention of cuticular pathogenesis in their 

microbe-saturated habitats. Digestion of some of the 

gleaned bacteria may be an auxiliary benefit, particularly 

if resident gut bacteria play a role in neutralizing ingested 

pathogens. Intense allogrooming in developmental stages 

with high nutrient requirements is suggestive that there 

may be a nutritional reward for the groomer, in the form 

of microbes, cuticular waxes, or other secretions. Starvation 

is known to increase grooming interactions in termites 

(Dhanarajan, 1978), and the observation that 

young Cryptocercus nymphs spend up to a fifth of their 

time grooming the heavily sclerotized adults, presumably 

the most pathogen-resistant stage, further supports this 

hypothesis. However, young nymphs also may be acquiring 

antimicrobials or other non-nutritive beneficial substances 

from adults during grooming, and keeping nest 

mates free of infection is in the best interest of the 

groomer as well as the groomee. Radiotracer studies are 

necessary to confirm the assimilation of ingested microbes. 

Flagellates as Food 

Trophic stages of protozoans are vulnerable when they 

are passed from adult to offspring during proctodeal 

trophallaxis in the wood-feeding cockroach Cryptocercus. 

Some flagellate species are extremely large—Barbulanympha 

may be up to 340 long (Cleveland et al., 

1934), and first instars of Cryptocercus are unusually small 

(Nalepa, 1996). Consequently, large flagellates may not be 

able to pass through the proventriculus of early instars 

without being destroyed; the phenomenon has been reported 

in termites. Remnants of the flagellate Joenia were 

observed in the gizzards of all young Kalotermes examined 

by Grassé and Noirot (1945). It may take several 

molting cycles before the gizzard of the young host is of a 

diameter to allow passage of the largest flagellates. Typically, 

the large protozoans are the last ones established in 

Cryptocercus; they are not habitually found in the hindgut 

until the third instar (Nalepa, 1990). Until then, the numerous 

flagellates passed from adult to offspring in the 

proctodeal fluids are a high-quality, proteinaceous food 

(Grassé, 1952) available at low metabolic cost to the consumer 

(Swift et al., 1979). The normal death of protozoans 

within the gut may also contribute to microbial 

protein in the hindgut fluids. Cleveland (1925) indicated 

that “countless millions of them must die daily” in a single 

host. 

Fungi as Food 

Fig 5.5 Grooming behavior. (A) Periplaneta americana passing 

an antenna through its mouth during autogrooming. Modified 

from Jander (1966), courtesy of Ursula Jander. (B) Fourth-instar 

Cryptocercus punctulatus allogrooming a sibling. Photo by 

C.A. Nalepa. 

Many animals feed on fungal tissue by selectively grazing 

on fruiting bodies and mycelia. Others consume small 

quantities of fungal tissue along with larger amounts of 

the substrate on which the fungus is growing (Kukor 

and Martin, 1986). Cockroaches as a group span both 

categories, using fungi as food either incidentally or 

specifically. 

Among the more selective feeders are species like Parcoblatta, 

which include mushrooms in their diet (Table 

4.1), and Lamproblatta albipalpus, observed grazing on 

mycelia covering the surface of rotten wood and dead 

leaves (Gautier and Deleporte, 1986). The live and dead 

plant roots used as food by the desert cockroach Arenivaga 

investigata are sheathed in mycorrhizae, and numerous 

fungal hyphae can be found in the crop (Hawke and 

Farley, 1973). Shelfordina orchidae eats pollen, fungal hy- 

82 COCKROACHES

phae, and plant tissue (Lepschi, 1989), and gut content 

analyses have clearly established that many species in 

tropical rainforest consume fungal hyphae and spores 

(WJB, unpubl. obs.). Australian Ellipsidion spp. are often 

associated with sooty mold, although it is not known if 

they eat it (Rentz, 1996). No known cockroach specializes 

on fungi, although species that live in the nests of fungusgrowing 

ants and termites may be candidates. 

All types of decaying plant tissues, whether foliage, 

wood, roots, seeds, or fruits, are thoroughly permeated by 

filamentous fungi (Kukor and Martin, 1986). The fungal 

contribution to the nutrient budget of cockroaches, however, 

is unknown. Chitin is the major cell wall component 

of most fungi and constitutes an average of 10% of fungal 

dry weight (range 2.6–26.2) (Blumenthal and Roseman, 

1957). Although chitinases are apparently rare in 

the digestive processes of most detritus-feeding insects 

(Martin and Kukor, 1984), it is distributed throughout 

the digestive tract of P. americana. The enzyme is related 

to cannibalism and the consumption of exuvia (Waterhouse 

and McKellar, 1961), but may also play a role in 

breaking down fungal polysaccharides. 

BACTEROIDS 

Bacteroids are symbiotic gram-negative bacteria of the 

genus Blattabacterium living in the fat body of all cockroaches 

and of the termite Mastotermes darwiniensis. The 

endosymbionts reside in specialized cells, called mycetocytes 

or bacteriocytes, with each symbiont individually 

enclosed in a cytoplasmic vacuole (Fig. 5.6A,C). They are 

transmitted between generations vertically, via transovarial 

transmission, a complex, co-evolved, and highly 

coordinated process (Sacchi et al., 1988; Wren et al., 1989; 

Lambiase et al., 1997; Sacchi et al., 2000). DNA sequence 

analyses indicate that the phyletic relationships of the 

bacteroids closely mirror those of their hosts, with nearly 

equivalent phylogenies of host and symbiont (Bandi et 

al., 1994, 1995; Lo et al., 2003a) (Fig. 5.7). Bacteroids synthesize 

vitamins, amino acids, and proteins (Richards and 

Brooks, 1958; Garthe and Elliot, 1971) but the symbiotic 

relationship appears grounded on their ability to recycle 

nitrogenous waste products and return usable molecules 

to the host (Cochran and Mullins, 1982; Cochran, 1985; 

Mullins and Cochran, 1987). The establishment of the 

urate-bacteroid system in the cockroach-termite lineage 

occurred at least 140 mya (Lo et al., 2003a), and was an 

elaborate, multi-step process. It involved the regulation 

or elimination of urate excretion, the intracellular integration 

of the bacteroids, the evolution of urate and 

mycetocyte cells in the fat body, and the coordination of 

the intricate interplay between host and symbionts during 

transovarial transmission (Cochran, 1985). 

Fig. 5.6 Transmission electron micrographs of the fat body of 

Cryptocercus punctulatus. (A) Bacteriocyte with cytoplasm 

filled by symbiotic bacteria (g glycogen granules; m mitochondria; 

arrows vacuolar membrane). Scale bar 2.2 

m. (B) Urocyte of C. punctulatus. Note the crystalloid subunit 

arranged concentrically around dark cores of urate structural 

units. Scale bar 0.8 m. (C) Detail of a bacteriocyte showing 

glycogen particles (arrows) both enclosed in a vacuolar 

vesicle and within the vacuolar space surrounding the bacteroid, 

suggesting exchange of material between host cell cytoplasm 

and the endosymbiont. Scale bar 0.5 m. From Sacchi 

et al. (1998a); photos courtesy of Luciano Sacchi. 


Fig. 5.7 Phylogeny of dictyopteran species and a comparison with the phylogeny of endosymbiotic 

Blattabacterium spp. The host phylogeny was based on a combined analysis of 18S rDNA and mitochondrial 

COII, 12S rDNA, and 16S rDNA sequences. Tree length: 2901, consistency index: 0.55. Bold 

lines indicate those dictyopteran taxa that harbor Blattabacterium spp., and that were examined in 

host endosymbiont congruence tests. The asterisk indicates the only node in the topology that was in 

disagreement with that based on host phylogeny. From Lo et al. (2003a), reprinted with permission 

from Nathan Lo and the journal Molecular Biology and Evolution. 

Urate Management 

Nitrogen excretion in cockroaches is a complex phenomenon 

that differs from the expected terrestrial insect pattern 

of producing and voiding uric acid. Several different 

patterns are apparent. The majority of species studied 

(thus far 80) do not void uric acid to the exterior even 

though they may produce it in abundance (Cochran, 

1985). When cockroaches are placed on a diet high in nitrogen, 

urates accumulate in their fat body (Mullins and 

Cochran, 1975a); they are typically deposited in concentric 

rings around a central matrix in storage cells (urocytes) 

adjacent to bacteriocytes (Cochran, 1985) (Fig. 

5.6B). When the diet is deficient in nitrogen or individual 

nitrogen requirements increase, bacteroids mobilize the 

urate stores for reuse by the host, and the fat body deposits 

become depleted. Uric acid storage thus varies directly 

with the level of dietary nitrogen and is not excreted 

under any conditions. Even when fed extremely high levels 

of dietary nitrogen, American and German cockroaches 

continue to produce and store uric acid in the fat 

body and other tissues, ultimately leading to their death 

(Haydak, 1953; Mullins and Cochran, 1975a). At least 

three other patterns of urate excretion are found in the 

family Blattellidae. In the Pseudophyllodromiinae, the 

genera Euphyllodromia, Nahublattella, Imblattella, and 

probably Riatia sparingly void urate-containing pellets, 

with urates constituting 0.5–3.0% of total excreta by 

weight (Cochran, 1981). Feeding experiments showed 

that high-nitrogen diets did not change urate output in 

Nahublattella nahua, but did increase it in N. fraterna in 

a dose-dependent manner. In both cases diets high in nitrogen 

content led to high mortality. The genus Ischnoptera 

(Blattellinae) excretes a small amount of urates 

(2% by weight) mixed with fecal material; this pattern is 

similar to that of other generalized orthopteroid insects, 

except for the very small amount of urates voided (Cochran 

and Mullins, 1982; Cochran, 1985). 

84 COCKROACHES

The most sophisticated pattern of nitrogen excretion 

occurs in at least nine species in the Blattellinae (Parcoblatta, 

Symploce, Paratemnopteryx), which void discrete, 

formed pellets high in urate content. These pellets 

are distinct from fecal waste (Fig. 5.8), suggesting that the 

packaging does not occur by chance. The cockroaches 

store urates internally as well (Cochran, 1979a). The level 

of dietary nitrogen in relation to metabolic demand for 

nitrogen is the controlling factor in whether uric acid is 

voided (Cochran, 1981; Cochran and Mullins, 1982; 

Lembke and Cochran, 1990). This is nicely illustrated in 

Fig. 5.9, which shows urate pellet excretion in female Parcoblatta 

fulvescens on different diets over the course of a 

reproductive cycle. Excreted urate pellets serve as a type 

of external nitrogen storage system, which may be accessed 

either by the excretor or by other members of the 

social group in these gregarious species. Reproducing females 

have been observed consuming the urate pellets, 

and they do so primarily when they are on a low-nitrogen, 

high-carbohydrate diet. A female carrying an egg 

case was even observed eating one, although they do not 

normally feed at this time. This system allows the cockroaches 

to deal very efficiently with foods that vary widely 

in nitrogen content. High nitrogen levels? The cockroaches 

store urates up to a certain level, and beyond that 

they excrete it in the form of pellets. Nitrogen limited? 

They mobilize and use their urate fat body reserves. Nitrogen 

depleted? They scavenge for high-nitrogen foods, 

including bird droppings and the urate pellets of conspecifics. 

Nitrogen unavailable? They slow or stop reproduction 

or development until it can be found (Cochran, 

1986b; Lembke and Cochran, 1990). 

Implications of the Bacteroid-Urate System 

The bacteroid-assisted ability of cockroaches to store, 

mobilize, and in some cases, transfer urates uniquely allows 

them to utilize nitrogen that is typically lost via excretion 

in the vast majority of insects (Cochran, 1985). 

These symbionts thus have a great deal of power in structuring 

the nutritional ecology and life history strategies 

of their hosts. Bacteroids damp out natural fluctuations 

in food availability, allowing cockroaches a degree of independence 

from the current food supply. An individual 

can engorge prodigiously at a single nitrogenous bonanza, 

like a bird dropping or a dead conspecific, then 

later, when these materials are required for reproduction, 

development, or maintenance, slowly mobilize the stored 

reserves from the fat body like a time-release vitamin. The 

legendary ability of cockroaches to withstand periods of 

starvation is at least in part based on this storage-mobilization 

physiology. The beauty of the system, however, is 

that stored urates are not only recycled internally by an 

individual, but, depending on the species, may be transferred 

to conspecifics, and used as currency in mating and 

parental investment strategies. Any individual in an ag- 

Fig. 5.8 “Salt and pepper” feces of Paratemnopteryx ( Shawella) couloniana; male, right; female 

and ootheca, left. The pile of feces to the left of the ootheca shows the variation in color of the 

pellets. Some of these have been separated into piles of the dark-colored fecal waste pellets (above 

the female) and the white, urate-filled pellets (arrow). Photo courtesy of Donald G. Cochran. 


ADDITIONAL MICROBIAL INFLUENCES 

Fig. 5.9 Urate pellet excretion by adult female Parcoblatta fulvescens 

in relation to the reproductive cycle and level of dietary 

nitrogen. Filled triangles, 4.0% nitrogen diet; filled circles, 

5.4% nitrogen diet; filled squares, 6.7% nitrogen diet. EC, egg 

case formation; ECD, egg case deposition. From Cochran 

(1986b), courtesy of Donald G. Cochran, with permission 

from Elsevier Press. 

gregation of the cockroaches that excrete urate pellets 

(like Parcoblatta) potentially benefits when just one of 

them exceeds its nitrogen threshold (Lembke and Cochran, 

1990). In cockroach species in which the male transfers 

urates to the female during or after mating (Mullins 

and Keil, 1980; Schal and Bell, 1982), it would not be surprising 

to discover that female mate or sperm choice decisions 

are based on the size or quality of the nuptial gift 

(Chapter 6). The diversity of modes of post-ovulation 

provisioning of offspring observed in cockroaches (brood 

milk, gut fluids, exudates) is likely to be rooted in the ability 

of a parent to mobilize and transfer stored reserves of 

nitrogen (Nalepa and Bell, 1997). Finally, cockroaches are 

able to use the uric acid scavenged from the feces of birds, 

reptiles, and non-blattarian insects, adding to the list of 

advantages of a generalized coprophagous lifestyle (Schal 

and Bell, 1982). 

Bacteroids as Food 

There is some evidence that fat body endosymbionts in 

cockroaches and in the termite Mastotermes may be a direct 

source of nutrients to developing embryos. During 

embryogenesis a portion of the bacterial population degenerates, 

with a concomitant increase in glycogen granules 

in the cytoplasm as the symbionts degrade (Sacchi et 

al., 1996, 1998b). Bacteroids are also reported to shrivel in 

size, then disappear when a postembryonic cockroach is 

starved (Steinhaus, 1946; Walker, 1965). 

There is a general under-appreciation of the ubiquity of 

microorganisms and the varied roles they play in the biology 

and life history of multicellular organisms. Microbes 

can affect their hosts and associates in unexpected 

ways, often with profound ecological and evolutionary 

consequences (McFall-Ngai, 2002; Moran, 2002). If this is 

true for organisms that are not habitually affiliated with 

rotting organic matter, shouldn’t microbial influence be 

exponentially higher in cockroaches, insects that seek 

out habitats saturated with these denizens of the unseen 

world? Our focus so far has been primarily on the role of 

microbes in the nutritional ecology of cockroaches. The 

diverse biosynthetic capabilities of microbes, however, allow 

for wide-ranging influences in cockroach biology. 

Microbes may alter or dictate the thermal tolerance of 

their host. Hamilton et al. (1985) demonstrated that the 

sugar alcohol ribitol acts as an antifreeze for C. punctulatus 

in transitional weather, and as part of a quick freeze 

system when temperatures drop. Because microbes produce 

significantly more five-carbon sugars than animals 

and because ribitol had not been previously reported in 

an insect, the authors suggested that microbial symbionts 

might be responsible for producing the alcohol or its precursors. 

Cleveland et al. (1934) indicated that the effects 

of temperature on the cellulolytic gut protozoans of 

Cryptocercus confine these insects to regions free from climatic 

extremes. These effects differ between the eastern 

and western North American species. If the insects are 

held at 20–23 o C, the protozoans of C. clevelandi die 

within a month, whereas those of C. punctulatus live 

indefinitely. 

Microbial products may act like pheromones. Because 

cockroach aggregation behavior is in part mediated by fecal 

attractants in several species, it is possible that gut microbes 

may be the source of at least some of the components. 

Such is the case in the aggregation pheromone of 

locusts (Dillon et al., 2000) and in the chemical cues that 

mediate nestmate recognition in the termite Reticulitermes 

speratus (Matsuura, 2001). 

Microbes may influence somatic development. There 

is a “constant conversation”between host tissues and their 

symbiotic bacteria during development, with the immune 

system of the host acting as a key player (McFall- 

Ngai, 2002). Aside from their profound effect on cockroach 

development via various nutritional pathways, 

bacterial mutualists may directly influence cockroach 

morphogenesis. It is known that gut bacteria are required 

for the proper postembryonic development of the gut in 

P. americana (Bracke et al., 1978; Zurek and Keddie, 

1996); normal intestinal function may depend on the 

induction of host genes by the microbes (Gilbert and 

86 COCKROACHES

Bolker, 2003). The highly complex and tightly coordinated 

interactions of Blattabacterium endosymbionts 

with their hosts during transovarial transmission and 

embryogenesis (Sacchi et al., 1988, 1996, 1998b) suggest 

that these symbionts may influence the earliest stages of 

cockroach development. 

MICROBES AS PATHOGENS 

Microbes can be formidable foes. Most animals battle infection 

throughout their lives, and devote substantial resources 

to responding defensively to microbial invaders 

(e.g., Irving et al., 2001). Cockroaches, like other animals 

that utilize rotting organic matter (Janzen, 1977), must 

fend off pathogenesis and avoid or detoxify the chemical 

offenses of microbes. Most Blattaria lead particularly 

vulnerable lifestyles. They are relatively long-lived insects 

that favor humid, microbe-saturated environments; 

many live in close association with conspecifics, particularly 

during the early, vulnerable part of life. They also 

have a predilection for feeding on rotting material, conspecifics, 

feces, and dead bodies. Pathogens and parasites 

such as protozoa and helminths (e.g., Fig. 5.10) are no 

doubt a strong and unrelenting selective pressure, but 

cockroach defensive strategies must be delicately balanced 

so that their vast array of mutualists are not placed 

in the line of fire. An example of these conflicting pressures 

lies in cockroach social behavior. On the one hand, 

beneficial microbes promote social behavior. Transmission 

of hindgut microbes requires behavioral adaptations 

so that each generation acquires microflora from the previous 

one, and consequently selects for association of 

neonates with older conspecifics. On the other hand, 

pathogenic microbes exploit cockroach social behavior, 

in that their transmission occurs via inter-individual 

Fig. 5.10 Hairworm parasite (Paleochordodes protus) of an 

adult blattellid cockroach (in or near the genus Supella) in 

Dominican amber (15–45 mya). From Poinar (1999); photo 

courtesy of George Poinar Jr. 

transfer. Oocysts of parasitic Gregarina, for example, are 

transmitted via feces (Lopes and Alves, 2005), and the biological 

control of urban pest cockroaches with pathogens 

is predicated largely on their spread via inter-individual 

contact in aggregations (e.g., Mohan et al. 1999; 

Kaakeh et al.,1996). Roth and Willis (1957) document inter-individual 

transfer of a variety of gregarines, coccids, 

amoebae, and nematodes via cannibalism, coprophagy, 

or proximity. 

Cockroaches have a variety of behavioral and physiological 

mechanisms for preventing and managing disease. 

At least two cockroach species recognize foci of potential 

infection and take behavioral measures to evade them. 

Healthy nymphs of B. germanica are known to avoid dead 

nymphs infected with the fungus Metarhizium anisopliae 

(Kaakeh et al., 1996). The wood-feeding cockroach Cryptocercus 

sequesters corpses and controls fungal growth in 

nurseries (Chapter 9). The former behavior may function 

to shield remaining members of the family from infection. 

Vigilant hygienic behavior or fungistatic properties 

of their excreta or secretions may also play a role throughout 

the gallery system. Fungal overgrowth of tunnels is 

never observed unless the galleries are abandoned (CAN, 

pers. obs.). 

The glandular system of cockroaches is complex and 

sophisticated, with seven types of exocrine glands found 

in the head alone (Brossut, 1973). The mandibular glands 

of two species (Blaberus craniifer and Eublaberus distanti) 

secrete an aggregation pheromone; otherwise the function 

of cephalic glands is unknown (Brossut, 1970, 1979). 

The secretion of some of these may have antimicrobial 

properties, and could be spread over the surface of the 

body to form an antibiotic “shell” during autogrooming, 

particularly if the cockroach periodically runs a leg over 

its head or through its mouthparts during the grooming 

behavioral sequence. Autogrooming therefore may function 

not only to remove potential cuticular pathogens 

physically, but also to disseminate chemicals that curtail 

their growth or spore germination. Dermal glands are 

typically spread over the entire abdominal integument of 

both males and females (200–400/mm 2 ) (Sreng, 1984), 

and five types of defensive-type exocrine glands have 

been described (Roth and Alsop, 1978) (Fig. 5.11). Most 

of the latter produce chemical defenses effective against 

an array of vertebrate and invertebrate predators (Fig. 

1.11A), but the influence of these chemicals on non-visible 

organisms is unexplored. They may well function as 

“immediate effronteries” to predators as well as “long 

term antagonists” to bacteria and fungi (Roth and Eisner, 

1961; Duffy, 1976), and act subtly, by altering growth 

rates, spore germination, virulence, or chemotaxis (Duffy, 

1976). Most cockroach exocrine glands produce multicomponent 

secretions (Roth and Alsop, 1978). The man- 


Fig. 5.11 Diagrammatic sagittal section of a cockroach abdomen, 

showing gland types I–IV and location of the secretory 

field for gland type V. One of the two type I glands has been 

omitted and its position indicated by an arrow. Only half of the 

medially opening Type III gland is shown. From Roth and Alsop 

(1978), after Alsop (1970), with permission from David W. 

Alsop. 

dibular glands of Eub. distanti, for example, is a blend of 

14 products (Brossut, 1979). Brossut and Sreng (1985) list 

93 chemicals from cockroach glands, some of which are 

known to be fungistatic in other systems, for example, 

phenols (Dillon and Charnley, 1986, 1995), naphthol, 

p-cresol, quinones (Brossut, 1983), and hexanoic acid 

(Rosengaus et al., 2004). Phenols have been identified 

from both the sternal secretions and the feces of P. americana, 

and neither feces nor the filter paper lining the 

floor of rearing chambers exhibit significant fungal 

growth (Takahashi and Kitamura, 1972). Other cockroaches 

also produce a strong phenolic odor when handled 

(Roth and Alsop, 1978). It is of interest, then, that 

phenols in the fecal pellets and gut fluids of locusts originate 

from gut bacteria, and are selectively bacteriocidal 

(Dillon and Charnley, 1986, 1995). Given the extraordinarily 

complex nutritional dynamics between cockroaches 

and microbes in the gut and on feces, these kinds 

of probiotic interactions are probably mandatory. It is a 

safe assumption that cockroaches engage in biochemical 

warfare with microbes, but they have to do so judiciously. 

Blattaria have both behavioral and immunological 

mechanisms for countering pathogens that successfully 

breach the cuticular or gut barrier. Wounds heal quickly 

(Bell, 1990), and cockroaches are known to use behavioral 

fever to support an immune system challenged by 

disease. When Gromphadorhina portentosa was injected 

with bacteria or bacterial endotoxin and placed in a thermal 

gradient, the cockroaches preferred temperatures 

significantly higher than control cockroaches (Bronstein 

and Conner, 1984). The immune system of cockroaches 

differs from that of shorter-lived, holometabolous insects, 

and mimics all characteristics of vertebrate immunity, 

including both humoral and cell-mediated responses 

(Duwel-Eby et al., 1991). Blaberus giganteus 

synthesizes novel proteins when challenged with fungi 

(Bidochka et al., 1997), and when American cockroaches 

are injected with dead Pseudomonas aeruginosa, they respond 

in two phases. Initially there is a short-term, nonspecific 

phase, which is superseded by a relatively longterm, 

specific response (Faulhaber and Karp, 1992). 

When challenged with E. coli, P. americana makes broadspectrum 

antibacterial peptides. Activity is highest 72–96 

hr after treatment, and newly emerged males respond 

best (Zhang et al., 1990). Cellular immune responses are 

mediated by hemocytes, primarily granulocytes and plasmatocytes 

(Chiang et al., 1988; Han and Gupta, 1988) 

whose numbers increase in response to invasion and 

counter it using phagocytosis and encapsulation (Verrett 

et al., 1987; Kulshrestha and Pathak, 1997). 

Sexual contact carries with it the risk of sexually transmitted 

diseases (e.g., Thrall et al., 1997), but no cockroaches 

were listed in an extensive literature survey on the 

topic (Lockhart et al., 1996). Wolbachia, a group of cytoplasmically 

inherited bacteria that are widespread among 

insects (including termites—Bandi et al., 1997) have not 

yet been detected in cockroaches, but few species have 

been studied to date (Werren, 1995; Jeyaprakash and Hoy, 

2000). Further surveys of Blattaria may yet detect Wolbachia, 

but because they are transmitted through the 

cytoplasm of eggs, these rickettsiae may have trouble 

competing with transovariolly transmitted bacteroids 

(Nathan Lo, pers. comm. to CAN). 

The cost of battling pathogens likely has life history 

consequences for cockroaches, since it does in many animals 

that inhabit more salubrious environments (Zuk and 

Stoehr, 2002). Immune systems can be costly in that they 

use energy and resources that otherwise may be invested 

into growth, reproduction, or maintenance, thus making 

them subject to trade-offs against other fitness components 

(Moret and Schmidt-Hempel, 2000; Møller et al., 

2001; Zuk and Stoehr, 2002). It may be possible, for example, 

that the prolonged periods of development typical 

of many cockroaches may be at least partially correlated 

with an increased investment in immune function. The 

life of a cockroach has to be a fine-tuned balancing act between 

exploiting, cultivating, and transmitting microbes, 

while at the same time suppressing, killing, or avoiding the 

siege of harmful members of the microbial consortia that 

surround them. Until recently, these relationships have 

been difficult to study because the microbes of interest are 

poorly defined, many have labile or nondescript external 

morphology, and most cannot be cultured in vitro. The 

availability of new methodology that allows insight into 

the origins, nature, and functioning of microbes (Moran, 

2002) in, on, and around cockroaches portends a bright 

future for studies on the subject. Until then, it should be 

considered that the ability of cockroaches to live in just 

about any organic environment may have its basis in their 

successful management of the varied, sophisticated, cooperative, 

and adversarial relationships with “inconspicuous 

associates” (Moran, 2002). 

88 COCKROACHES

SIX 

Mating Strategies 

The unfortunate couple were embarrassed beyond all mortification, not simply 

for having been surprised in the act by the minister, but also for their inability to 

separate, to unclasp, to unlink, to undo all the various latches, clamps and sphincters 

that linked them together, tail to tail in opposite directions. 

—D. Harington, The Cockroaches of Stay More 

The genitalia of male cockroaches are frequently used as an example of the extreme complexity 

that may evolve in insect reproductive structures (e.g., Gwynne, 1998). They have 

been likened to Swiss army knives in that a series of often-hinged hooks, tongs, spikes, 

and other lethal-looking paraphernalia are sequentially unfolded during copulation. 

Marvelous though all that hardware may be, it has not yet inspired research on its functional 

significance. Seventy years ago Snodgrass (1937) stated that “we have no exact information 

on the interrelated functions of the genital organs” of cockroaches, and the 

situation has improved only slightly since that time. While there is a vast literature on 

pheromonal communication, reproductive physiology, male competition, and behavioral 

aspects of courtship in cockroaches, we know surprisingly little about the “nuts and 

bolts” of the copulatory performance, and in particular, how the male and female genitalia 

interact. 

Here we briefly describe cockroach mating systems, and the basics of mate finding, 

courtship, and copulation. We then focus on just a few topics that are, in the main, relevant 

to the evolution of cockroach genitalia. We make no attempt to be comprehensive. 

Our emphasis is on male and female morphological structures whose descriptions are 

often tucked away in the literature on cockroach systematics and are strongly suggestive 

of sperm competition, cryptic mate choice, and conflicts of reproductive interest. One 

goal is to shift some limelight to the female cockroach, whose role in mating dynamics is 

poorly understood yet whose morphology and behavior suggest sophisticated control 

over copulation, sperm storage, and sperm use. 

MATING SYSTEM 

In nearly all cockroach species studied, males will mate with multiple females even if the 

exhaustion of mature sperm and accessory gland secretions preclude the formation of a 

spermatophore (Roth, 1964b; Wendelken and Barth, 1987); cockroach mating systems 

89

are therefore best classified on the basis of female behavior. 

However, it is difficult to determine how many mating 

partners a female has in the wild, and, as might be expected 

for insects that are mostly cryptic and nocturnal, 

field studies of mating behavior are rare. 

One Male, One Copulation 

Females of at least two cockroach species are reported to 

be monandrous in the strictest sense of the word. Once 

mated, Neopolyphaga miniscula (Jayakumar et al., 2002) 

and Therea petiveriana (Livingstone and Ramani, 1978) 

females remain refractory to subsequent insemination 

for the rest of their lives; the latter repel suitors by kicking 

with their hind legs. 

One Male, Multiple Copulations 

Wood-feeding cockroaches in the genus Cryptocercus 

may be described as socially monogamous; males and females 

establish long-term pair bonds and live in family 

groups. Genetic monogamy is yet to be determined, but 

opportunities for extra-pair copulations are probably 

few. When paired with a female, males fight to exclude 

other males from tunnels (Ritter, 1964), and adults of 

both sexes in families defend against intruders (Seelinger 

and Seelinger, 1983). In the two copulations observed in 

C. punctulatus, one lasted for 34 min and the other for 

42 min (Nalepa, 1988a); sneaky extra-pair copulations 

therefore seem unlikely. The best opportunity for cheating, 

if it occurs, would be after adult emergence but prior 

to establishment of a pair bond. Adult males and adult females 

each can be found alone in galleries, particularly 

during spring and early summer field collections (Nalepa, 

1984). 

Typically, males and females pair up during summer, 

overwinter together, and produce their sole set of offspring 

the following summer. Although sperm from a 

single copulation are presumably sufficient to fertilize 

these eggs (average of 73), pairs mate repeatedly over the 

course of their association. There is evidence of sexual activity 

the year before reproduction, immediately prior to 

oviposition, during the oviposition period, after the hatch 

of their oothecae, and 1 yr after the hatch of their single 

brood (Nalepa, 1988a). Prior to oviposition, repeated 

copulation may function as paternity assurance or perhaps 

nutrient transfer, but mating after the eggs are laid 

is more difficult to explain. Rodríguez-Gironés and Enquist 

(2001) note that mating frequency is particularly 

high in species where males associate with females and 

assist them in parental duties. Superfluous copulations 

evolve in these pairs because females attempt to sequester 

male assistance and males are deprived of cues about female 

fertility. It would be of interest to determine if this 

pattern of repeated mating behavior occurs in other socially 

monogamous, wood-feeding cockroaches like Salganea; 

these also live in family groups with long-term 

parental care (Matsumoto, 1987; Maekawa et al., 2005). 

Multiple Males, One Copulation 

per Reproductive Cycle 

In most studied cockroaches female receptivity is cyclic. 

It declines sharply after copulation and is not restored until 

after partition. In some species it takes several reproductive 

cycles before another mating partner is accepted, 

in others receptivity is restored following each reproductive 

event. Females, then, may be described as monandrous 

within each period that they are accepting mates, 

but polyandrous over the course of their reproductive life. 

Because they store sperm, it is only during the formation 

of the first clutch of eggs that their partners are under little 

threat from sperm competition. The pattern of cyclic 

receptivity occurs in both oviparous and live-bearing 

cockroaches. Both Blattella germanica (Cochran, 1979b) 

and B. asahinai (Koehler and Patternson, 1987) may copulate 

repeatedly, although a single mating usually provides 

sufficient sperm to last for the reproductive life of 

the female. Periplaneta americana females alternate copulation 

with oothecal production, and may mate as soon 

as 3–4 hr after depositing an egg case (Gupta, 1947). A 

pair of Ellipsidion humerale ( affine) were observed 

copulating four times within a month, alternating with 

oothecal production (Pope, 1953). Similarly, blaberid females 

ordinarily mate just once prior to their first oviposition. 

After eclosion of the nymphs, they may then enter 

another cycle of receptivity, mating, oviposition, and egg 

incubation (Engelmann, 1960; Roth, 1962; Roth and 

Barth, 1967; Grillou, 1973). Once mated, female Eublaberus 

posticus are fertile for life, and remating does 

not improve reproductive performance (Roth, 1968c); 

nonetheless, remating has been observed (Darlington, 

1970). 

Multiple Males, Multiple Copulations 

per Reproductive Cycle 

Reports of multiple mating by a female within a single reproductive 

cycle exist, but they are the exception rather 

than the rule among examined species. In his study of 

more than 200 female B. germanica, Cochran (1979b) 

recorded just a single instance of a female mating twice 

prior to her first egg case. In their extensive studies of the 

same species, Roth and Willis (1952a) noted one pair that 

copulated twice within a 24-hr period. Hafez and Afifi 

(1956) report that in Supella longipalpa “copulation may 

90 COCKROACHES

occur once or twice a day” but give no further details. On 

rare occasions, a female of Diploptera punctata may be 

found carrying two spermatophores; however, one of 

these is always improperly positioned (Graves, 1969). 

Sperm are likely transferred only from the one correctly 

aligned with the female’s spermathecal openings (discussed 

below). 

MATE FINDING 

Most cockroaches that have been studied rely on chemical 

and tactile cues to find their mates in the dark (Roth 

and Willis, 1952a). In many cases volatile sex pheromones 

mediate the initial orientation; these have been demonstrated 

in 16 cockroach species in three families. The 

pheromones are most commonly female generated and 

function at a variety of distances, up to 2 m or more, depending 

on the species (Gemeno and Schal, 2004). Females 

in the process of releasing pheromone (“calling”) 

often assume a characteristic posture (Fig. 6.1): they raise 

the wings (if they have them), lower the abdomen, and 

open the terminal abdominal segments to expose the genital 

vestibulum (Hales and Breed, 1983; Gemeno et al., 

2003). In some species the initial roles are reversed, with 

males assuming a characteristic stance while luring females 

(Roth and Dateo, 1966; Sreng, 1979a). A calling 

male may maintain the posture for 2 or more hr, with 

many short interruptions (Sirugue et al., 1992). Based on 

the limited available data, the general pattern appears to 

be that in species where the male or both sexes are volant, 

females release a long-range volatile pheromone. Males 

release sex pheromones in species where neither sex can 

fly (Gemeno and Schal, 2004). 

Non-chemical Cues 

Fig. 6.1 Calling behavior in female Parcoblatta lata. Females in 

the calling posture raise the body up from the substrate and alternate 

between two positions: (A) upward with longitudinal 

compression, and (B) downward with longitudinal extension. 

From Gemeno et al. (2003), courtesy of César Gemeno, with 

permission of Journal of Chemical Ecology. 

Fig. 6.2 Male Lucihormetica fenestrata Zompro & Fritzsche, 

1999 (holotype) exhibiting its pronotal “headlights.” Copyright 

O. Zompro, courtesy of O. Zompro. 

While research has focused primarily on chemical cues 

(and justly so), mate finding and courtship may be multimodal 

in a number of species, that is, they integrate 

chemical, visual, tactile, and acoustic signals. Vision apparently 

plays little or no significant role in sexual recognition, 

courtship, or copulation in the species typically 

studied in laboratory culture (Roth and Willis, 1952a). 

However, in many cockroaches the males have large, welldeveloped, 

pigmented eyes, suggesting the possibility that 

optical cues may be integrated with pheromonal stimuli 

during mate seeking and mating behavior. Visual orientation 

seems particularly likely in Australian Polyzosteriinae 

and in brightly colored, diurnally active blattellids. 

The delightful discovery of pronotal headlights on males 

of Lucihormetica fenestrata suggests that even nocturnally 

active cockroaches may use sight in attracting or courting 

mates (Zompro and Fritzsche, 1999). This species lives in 

bromeliads in the Brazilian rainforest and has two elevated, 

kidney-shaped, strongly luminescent organs on the 

pronotum (Fig. 6.2). These protuberances are highly 

porous (probably to allow gas exchange) and absent in 

nymphs and females. Males of several related species 

sport similar structures, but because live material had 

never been examined, their function as lamps was unknown. 

COURTSHIP AND COPULATION 

Once in the vicinity of a potential mate, contact pheromones 

on the surface of the female and short-range 

volatiles produced by the male facilitate sexual and 

species recognition and coordinate courtship. Recently 

the topic was comprehensively reviewed by Gemeno 

and Schal (2004). Developments in the field worth noting 

include the finding that short-range and contact 

pheromones not only mediate mate choice and serve as 

behavioral releasers during courtship, but may regulate 

physiological processes as well. The phenomenon is best 

studied in Nauphoeta cinerea, where male pheromones 

may influence female longevity, the number and sex ratio 

of offspring, and their rate of development in the brood 

sac (Moore et al., 2001, 2002, 2003). 

MATING STRATEGIES 91

Fig. 6.3 “Basics” of type I courtship and copulation in cockroaches, 

after initial orientation to a potential mate. 

With few exceptions, pre-copulatory behavior is remarkably 

uniform among cockroaches (Roth and Willis, 

1954b; Roth and Dateo, 1966; Roth and Barth, 1967; 

Roth, 1969; Simon and Barth, 1977a). Antennal contact 

with the female usually instigates a male tergal display 

(Fig. 6.3); he turns away from her and presents the dorsal 

surface of his abdomen. The female responds by climbing 

onto his back and “licks” it, with the palps and mouthparts 

closely applied and working vigorously. The “female 

above” position lasts but a few seconds before the male 

backs up and extends a genitalic hook that engages a small 

sclerite in front of her ovipositor. Once securely connected, 

he moves forward, triggering the female to rotate 

180 degrees off his back. The male abdomen untwists and 

recovers its normal dorsoventral relationship almost immediately. 

The pair remains in the opposed position until 

copulation is terminated. 

Although the final position assumed by cockroaches in 

copula is invariably end to end, there are two additional 

behavioral sequences that may precede it. Both are characterized 

by the lack of a wing-raising display and female 

feeding behavior. 

Type II mating behavior is characterized by the male 

riding the female, and is known in Pycnoscelus indicus and 

Jagrehnia madecassa. After the male contacts the female 

he crawls directly onto her back. He twists the tip of his 

abdomen down and under that of the female, engages her 

genitalia, then dismounts and assumes the opposed position 

(Roth and Willis, 1958b; Roth, 1970a; Sreng, 1993). 

In type III pre-copulatory behavior, neither sex mounts 

the other. After contact is made between the sexes, the 

male typically positions himself behind the female with 

his head facing in the opposite direction, then moves 

backward until genitalic contact is established. Cockroaches 

that fall into this category include Gromphadorhina 

portentosa (Barth, 1968c), Panchlora nivea (Roth 

and Willis, 1958b), Pan. irrorata (Willis, 1966), The. petiveriana 

(Livingstone and Ramani, 1978), Panesthia australis 

(Roth, 1979c), and the giant burrowing cockroach 

Macropanesthia rhinoceros. Mating in the latter has been 

described as being “like two Fiats backing into each 

other” (D. Rugg, pers. comm. to CAN) (Fig. 6.4). In Epilampra 

involucris, the male arches his abdomen down and 

then up in a sweeping motion until he contacts the female’s 

genitalia (Fisk and Schal, 1981). In Panesthia cribrata, 

the two sexes start out side by side. The female 

raises the tip of her abdomen and the male bends toward 

the female until the tips of their abdomens are in close 

proximity. The male then turns 180 degrees to make genital 

contact (Rugg, 1987). It is of interest that type III precopulatory 

behavior occurs in the Polyphagidae (Therea), 

and in four different subfamilies of Blaberidae. A common 

thread is that most of these cockroaches are strong 

burrowers, suggesting that the behavior may be an adaptation 

to some aspect of their enclosed lifestyle. It is also 

notable that termites initiate copulation by backing into 

each other (Nutting, 1969). 

Acoustic Cues 

In some cockroach species mating behavior is highly 

stereotyped, with an internally programmed, unidirec- 

Fig. 6.4 Copulating pair of Macropanesthia rhinoceros, a species 

with type III mating behavior. Photo courtesy of Harley 

Rose. 

92 COCKROACHES

tional sequence of acts (Bell et al., 1978); in others, malefemale 

interaction is more flexible (Fraser and Nelson, 

1984). Variations that do occur often take the form of 

behaviors that produce airborne or substrate-borne vibrations, 

particularly when males are courting reluctant 

females (Fig. 6.5). These signals typically occur after 

antennal contact but prior to full tergal display, and 

include rocking, shaking, waggling, trembling, vibrating, 

pushing, bumping, wing pumping, wing fluttering, 

“pivot-trembling,” anterior-posterior jerking, hissing, 

whistling, tapping, and stridulation. Although Barth 

(1968b) suggested that vibrating and wing fluttering during 

courtship produce air currents that serve to disseminate 

pheromone, very little is known regarding the role of 

these behaviors in influencing female receptivity. Hissing 

during courtship is best known in G. portentosa (Fraser 

and Nelson, 1984), but occurs in other species as well. 

Males of Australian burrowing cockroaches pulse the abdomen 

during courtship, and the behavior is accompanied 

by an audible hiss in the larger species (D. Rugg, pers. 

comm. to CAN). Elliptorhina chopardi males produce 

broad-band, amplitude-modulated hisses like G. portentosa, 

but also complex, bird-like whistles; dual harmonic 

series warble independently from the left and right fourth 

spiracle (Fraser and Nelson, 1982; Sueur and Aubin, 

2006). The common name of Rhyparobia maderae is the 

“knocker” cockroach, because of the male habit of tapping 

the substrate with his thorax in the presence of potential 

mates (Fig. 6.5B). Highly developed stridulating 

organs are found on the pronotum and tegmina of some 

Blaberidae (Oxyhaloinae and Panchlorinae) (Roth and 

Hartman, 1967; Roth, 1968c). Males of Nauphoeta cinerea 

use the structures to produce characteristic phrases consisting 

of complex pulse trains and chirps if a female is 

unresponsive to his overtures (Hartman and Roth, 1967a, 

1967b). There is currently no evidence, however, that the 

male’s distinctive song (Fig. 6.5D) influences her response. 

Sounds produced by N. cinerea during courtship 

can be recorded from the substrate on which they are 

standing as well as by holding a microphone at close range 

(Roth and Hartman, 1967). Given the evidence that cockroaches 

can be sensitive to vibration as well as airborne 

sound (Shaw, 1994a), substrate-borne courtship signals 

may be more common than is currently appreciated. This 

is especially relevant for tropical cockroaches that perch 

at various levels in the canopy during their active period. 

Bell (1990) noted that cockroaches on leaves can detect 

the vibrations of approaching predators. These cockroach 

species also have potential for communicating with 

each other via leaf tremulation. The cockroach “ear”is the 

subgenual organ on the metathoracic legs, a fan-shaped 

structure lying inside and attached to the walls of the tibiae. 

The subgenual organ of P. americana is one of the 

Fig. 6.5 Oscilloscope records of sounds in cockroaches. (A) 

Arrhythmic rustling sound made by a courting male Eublaberus 

posticus; (B) sound produced by a male Rhyparobia 

maderae tapping upon the substrate, which in this case, was a 

female on which the male was standing; (C) courting sounds 

produced by a male Diploptera punctata by striking the wings 

against the abdomen; (D) phrase produced by stridulation 

during courtship in male Nauphoeta cinerea; compare to (E) 

disturbance sound made by male N. cinerea. After Roth and 

Hartman (1967); see original work for reference signals and 

sound levels. 

most sensitive known insect vibration detectors (Autrum 

and Schneider, 1948; Howse, 1964). 

Length of Copulation 

The length of copulation is variable in cockroaches, both 

within and between species. In successful matings, the 

male and female commonly remain in the linear position 

for 50–90 min, but length can vary with male age, the 

time since his last mating, and his social status. The shortest 

recorded copulations are in the well-studied N. 

cinerea. A male’s first copulation is his shortest, ranging 

from 9.5 (Moore and Breed, 1986) to 17 (Roth, 1964b) 

min. Dominant males of this species copulate significantly 

longer than do their subordinates (Moore and 

Breed, 1986; Moore, 1990). If males 14–15 days old are 

consecutively mated to a series of females, they remain in 

copula 22 min during the first mating, 100 in the second, 

and 141 in the third (Roth, 1964b). The most extended 

matings reported from natural settings are those of Xestoblatta 

hamata, where copulation in the rainforest may last 

for up to 5 hr (Schal and Bell, 1982), and Polyzosteria limbata, 

where copulation occurs in daylight and pairs sometimes 

remain linked for over 24 hr (Mackerras, 1965a). 

Spermatophores 

In all cockroach species the male transfers sperm to the 

female via a spermatophore; it begins forming in the male 

as soon as the mating pair is securely connected (Khalifa, 

1950; van Wyk, 1952; Roth, 2003a). When it is complete, 

the spermatophore in Blattella descends the ejaculatory 


duct and is pressed by the male’s endophallus against the 

female genital sclerites (Khalifa, 1950). In Periplaneta the 

spermatophore is not discharged until at least an hour 

from the beginning of copulation (Gupta, 1947). In N. 

cinerea, where copulation length is typically short, mating 

pairs detached after 10–12 min can be separated into 

three groups. In some, only a copious secretion is present; 

in others a spermatophore has been transferred but is not 

secured. A third group has a spermatophore firmly inserted 

(Roth, 1964b). 

Three spermatophore layers can be distinguished in 

Blattella: a clear, transparent section covering the ventral 

surface, a lamellated portion that forms the dorsal wall, 

and at its core, suspended in a milky white mass, are two 

sacs containing the sperm (Khalifa, 1950). Periplaneta’s 

spermatophore has just one sperm sac (Jaiswal and 

Naidu, 1976). In Blaberus craniifer the spermatophore 

consists of four heterogeneous layers, and is invested with 

a variety of enzymes including proteases, esterases, lipases, 

and phosphatases (Perriere and Goudey-Perriere, 

1988). Several mechanisms exist for fixing the spermatophore 

in the female (Graves, 1969): (1) the soft outer 

layer hardens against the female genital sclerites (Blattinae); 

(2) a thick, wax-like shell holds it in place (most 

Blattellidae); (3) a large quantity of glue-like secretion secures 

it (Blaberinae, one Zetoborinae); (4) a uniquely 

shaped, elongated spermatophore is enclosed in a large 

membranous bursa copulatrix in the female (Diplopterinae, 

Oxyhaloinae, Panchlorinae, Pycnoscelinae, one Zetoborinae). 

When transferring the spermatophore, the male orients 

its tip so that the openings of the sperm sacs are 

aligned directly with the female spermathecal pores 

(Khalifa, 1950; Roth and Willis, 1954b; Gupta and Smith, 

1969); this is apparently unusual among insects (Gillott, 

2003). The sperm do not migrate from the spermatophore 

until copulation is terminated. When first transferred, 

the spermatophore of N. cinerea contains nonmotile, 

twisted sperm; they became active about 2 hr later. 

Two to three days after mating only a few sperm remain 

in the spermatophore but the spermathecae are densely 

filled with them (Roth, 1964b; Vidlička and Huckova, 

1993). If the spermatophore is removed 25 min after the 

male and female detach in B. germanica, “a thin thread of 

spermatozoa, hair-like in appearance, may extend from 

the female’s spermathecal opening” (Roth and Willis, 

1952a). It takes about 5 hr for sperm to migrate into the 

spermathecae of D. punctata (Roth and Stay, 1961). The 

stimulus for sperm activation may be in male accessory 

gland secretions transferred along with the sperm (Gillott, 

2003), produced by the female in the spermathecae 

or spermathecal glands (Khalifa, 1950; Roth and Willis, 

1954b), or both. Little is known regarding the mechanism 

by which sperm move from the spermatophore to the 

spermatheca. Among the nonexclusive hypotheses are the 

active motility of sperm, migration in chemotactic response 

to spermathecal or spermathecal gland secretions, 

contractions of visceral muscles associated with the female 

genital ducts, and aspiration by pumping movements 

of the musculature of the spermatheca (Gupta and 

Smith, 1969). Male accessory gland secretions may play a 

role in stimulating female muscle contraction (Davey, 

1960). The activity and morphology of sperm may 

change once they reach the spermatheca. In Periplaneta, 

alterations were noted chiefly in the acrosome (Hughes 

and Davey, 1969). 

Sperm Morphology 

Cockroaches have extremely thin sperm, with long, actively 

motile flagellae (Baccetti, 1987). The sperm head 

and the tail are indistinguishable in some species, such as 

B. germanica, but can be distinct and variable among 

other examined cockroaches. The sperm head in Arenivaga 

boliana, for example, is helical, and that of Su. longipalpa 

is extremely elongated (Breland et al., 1968). Total 

sperm length varies considerably, with B. germanica and 

P. americana at the extremes of the range in 10 examined 

cockroach species (Breland et al., 1968). The limited data 

we have suggest that body size and sperm length may be 

negatively correlated (Table 6.1), but the relative influences 

of body size, cryptic choice mechanisms, and sperm 

competition have not been studied. 

Dimorphic sperm have been described in P. americana 

(Richards, 1963). A small proportion are “giants,” sperm 

that have big heads and tails that are similar in length but 

two or more times the diameter of typical sperm. These 

chunky little gametes swim at approximately the same 

speeds as the “normal,” more streamlined, sperm, and are 

thought to be the result of multinucleate, diploid, or 

Table 6.1. Sperm length relative to body length in cockroaches. 

Sperm data from Jamieson (1987) and Vidlička and Huckova 

(1993). 

Approximate 1 Sperm Ratio body 

body length length length:sperm 

Species length (mm) (µ) length 

Blattella germanica 12.0 450 27:1 

Pycnoscelus indicus ~ 21.0 2 250 84:1 

Nauphoeta cinerea 27.0 300 90:1 

Periplaneta americana 37.5 85 441:1 

Blaberus craniifer 55.0 180 306:1 

1 

Body length can range fairly widely within a species, for example, male 

B. germanica ranges from 9.6 to 13.8 mm in length (Roth, 1985). 

2 

Body length based on its sibling species, Pyc. surinamensis. 

94 COCKROACHES

higher degrees of heteroploidy. Giants range from 0–30% 

of the total in testes; smears from either seminal vesicles 

or spermathecae of females, however, yield a much lower 

percentage, just 0–2%. Most never leave the male gonads, 

and it is unknown whether those that do are capable of 

effecting fertilization. Alternate sperm forms are fairly 

common among invertebrates, and in some cases are specialized 

for functions in addition to or instead of fertilization 

(Eberhard, 1996). These include acting as nuptial 

gifts, suppressing the female’s propensity to remate, and 

creating a hostile environment for rival sperm (e.g., 

Buckland-Nicks, 1998). The topic is thoroughly discussed 

in Swallow and Wilkinson (2002). 

Sperm Competition 

When the probability of female remating is high, selection 

should favor adaptations in males that allow them to 

reduce or avoid competition with the sperm of another 

male. This can lead to rapid and divergent evolution of 

traits that function in sperm competition and its avoidance. 

These traits may be manifest in behavior (e.g., mate 

guarding), genital morphology (e.g., structures that deliver 

sperm closer to the spermatheca), and physiology 

(e.g., chemicals in the ejaculate that enhance the success 

of sperm). Selection may also act at the level of the sperm 

itself, in that some may be adapted to outcompete others 

for access to eggs (Ridley, 1988; Eberhard, 1996; Simmons, 

2001). 

In studies of sperm competition paternity is typically 

reported as P 2 

, the proportion of offspring sired by the 

last male to mate with a female in controlled double mating 

studies (Parker, 1970). A P 2 

between 0.4 and 0.7 indicates 

sperm mixing. A P 2 

higher than 0.8 suggests that 

sperm are either lost prior to the second mating, or that 

second-male sperm precedence or displacement is in operation. 

Values of 0.4, where the first male is favored, 

are rare (Simmons, 2001). 

Classical studies of sperm competition have been conducted 

in two cockroach species: B. germanica and D. 

punctata. Cochran (1979b) studied the phenomenon in 

the German cockroach and used the genetic mutant rose 

eye to recognize paternity. In the single instance of a female 

mating twice prior to the first egg case, the second 

male sired 95% of the eggs. Just over 20% of females remated 

between egg cases; Gwynne (1984), using Cochran’s 

data, calculated the P 2 

of these to be 0.43. Using a 

slightly different approach with the same data, Simmons 

(2001, Table 2.1) calculated the P 2 

as 0.69 when mutant 

males were the first to mate and 0.33 when wild-type 

males were the first to mate. The P 2 

calculated using 

mixed broods only was 0.37 (Simmons, 2001, Table 

2.3). Blattella is exceptional, then, in that the general 

Fig. 6.6 Sperm competition in Blattella germanica. Virgin females 

with the recessive eye color mutation rose eye were initially 

mated to a mutant male, then to a wild-type male (top 

graphs), or first to a wild-type male, and subsequently to another 

mutant (bottom graphs). In each case the female was exposed 

to the second male only after her first egg case began protruding; 

progeny of the first egg case were thus sired exclusively 

by the initial male. Inset graphs detail the paternity of nymphs 

from oothecae of mixed parentage, that is, those containing 

eggs fertilized by both males. After data in Cochran (1979b), 

with permission of D.G. Cochran. 

trend is first-male precedence. A focus on average P 2 

values 

can be misleading, however, because variation within 

a species can be extreme (Lewis and Austad, 1990; Eberhard, 

1996). A detailed examination of Cochran’s data indicates 

that in most reproductive episodes, the eggs of 

some oothecae were exclusively fathered by the first male, 

some were exclusively fathered by the second male, and 

some were of mixed parentage (Fig. 6.6). In the waning 


stages of the female’s reproductive life sperm from the 

second male sired a higher proportion of the offspring, 

suggesting that remating may occur in response to declining 

sperm supply (Cochran, 1979b). Maternal influence 

may account for some variation in paternity. Females 

have four spermathecae, each with a separate 

opening, and thus potential for selective sequestration 

and release of sperm (discussed below). It is noteworthy, 

based on the P 2 

values cited above, that either the sperm 

of mutant males are somewhat inferior competitors, or 

that females exhibit some preference for the sperm of 

wild-type males. 

Woodhead (1985) used irradiated males to examine 

sperm competition in D. punctata, a viviparous cockroach 

that remates only after partition of the first brood. 

The P 2 

averaged 0.67 but was higher when the second 

male was the normal male (0.89), rather than the irradiated 

male (0.46). Plots of the position of viable versus 

sterile eggs in individual oothecae suggested sperm mixing; 

there was no consistent spatial pattern of egg fertilization 

by the two sires. The spermatheca in Diploptera females 

is tubular, a shape usually associated with sperm 

stratification (Walker, 1980). 

Variation in Ejaculates 

A number of studies indicate that males increase the size 

of their ejaculate in the presence of rival males (summarized 

in Wedell et al., 2002). Harris and Moore (2004) 

tested the idea in N. cinerea by exposing adult males during 

their post-emergence maturation period to the chemical 

presence of potential competitors (other males) or 

mates (females); spermatophore size, testes size, and 

sperm numbers were then determined and compared to 

isolated male controls. The authors could not demonstrate 

an influence of male competitors on testes size or 

sperm number. Spermatophore size increased in the presence 

of either sex, suggesting the possibility of a group effect 

on this reproductive character. Males did transfer 

significantly more sperm during copulation when, after 

adult emergence, they matured in the presence of females 

rather than males. One caution in interpreting this study 

is that the development of the testes and the production 

of sperm in Nauphoeta may be largely complete prior to 

adult emergence, as it is in G. portentosa, Byrsotria fumigata 

(Lusis et al., 1970), Blatta orientalis (Snodgrass, 

1937), and P. americana (Jaiswal and Naidu, 1972). 

Hunter and Birkhead (2002) addressed the relationship 

between sperm competition and sperm quality by 

comparing the viability of male gametes in species pairs 

with contrasting mating systems. They found a higher 

percentage of dead sperm in N. cinerea, which the authors 

considered monandrous, than in D. punctata, which they 

considered polyandrous. It is unclear, however, as to how 

much the mating systems in these two species differ. Female 

Diploptera typically mate just after adult emergence, 

then carry the spermatophore until shortly before the 

ootheca is formed. They readily remate after partition of 

the first brood (Stay and Roth, 1958; Woodhead, 1985). 

Similarly, virgin female Nauphoeta are unreceptive after 

their first copulation; after partition, they may or may not 

mate again (Roth, 1962). Females of both species, then, 

may be considered monandrous during their first reproductive 

period, but polyandrous over the course of their 

lifetime. 

MALE INVESTMENT: TERGAL GLANDS 

“Tergal gland” is a generalized term describing a great 

variety of functionally similar glandular structures that 

have evolved on the backs of males (Roth, 1969). Male 

tergal glands occur in almost all cockroach families, but 

are rare in Polyphagidae and Blaberidae. Within the latter, 

the glands are restricted to the Epilamprinae and Oxyhaloinae. 

The most complex and morphologically varied 

glands occur in male Blattellidae, but at least 73 blattellid 

genera have species that lack these specializations (Roth, 

1969, 1971a; Brossut and Roth, 1977). 

Males display their tergal glands to potential mates 

during the wing-raising (or in wingless species, “backarching”) 

phase of courtship. The female responds by approaching 

the male, climbing on his dorsum, and feeding 

on the gland secretion. The glands thus serve to maneuver 

the female into the proper pre-copulatory position 

and arrest her movement so that the male has an opportunity 

to clasp her genitalia (Roth, 1969; Brossut and 

Roth, 1977). The extraordinary morphological complexity 

of the glands in some taxa, however, suggests that they 

may serve additional roles in courtship and mating. 

Morphology and Distribution 

When present in the Blattidae, tergal glands almost always 

occur on the first abdominal tergite. In Blattellidae as 

many as five segments may be specialized, but most genera 

in this family have just one tergal gland, usually on 

segment 1, 2, or 7 (Roth, 1969; Brossut and Roth, 1977). 

There are many genera where males either have or lack 

tergal glands. Among species of Parcoblatta, for example, 

males may have glands on the first tergite only, on the first 

and second tergites, or they may be absent (Hebard, 

1917). In Australian Neotemnopteryx fulva, the tergal 

gland on the seventh tergite ranges from a pair of dense 

tufts to a few, nearly invisible, scattered setae; Roth 

(1990b) illustrates four variations. Uniquely among cockroaches, 

the gland of Metanocticola christmasensis is on 

the metanotum (Roth, 1999b). The “best” positions are 

96 COCKROACHES

mounting by the female. Nonetheless, females of C. punctulatus 

have been observed straddling the male prior to 

assuming the opposed position (Nalepa, 1988a). 

Because tergal glands are often markedly different 

among different genera and species, they can be useful 

characters in cockroach taxonomy (Brossut and Roth, 

1977; Bohn, 1993). Morphologically they range from very 

elaborate cuticular modifications to the complete absence 

of visible structures. The glands may take the form 

of shallow or deep pockets containing knobs, hairs, or 

bristles (Fig. 6.7), fleshy protuberances, cuticular ridges, 

groups of agglutinated hairs, tufts or concentrations of 

setae, or just a few setae scattered on the tergal surface. In 

species with no externally visible specializations, internal 

cuticular reservoirs nonetheless may be present (Roth, 

1969; Brossut and Roth, 1977). Sometimes secretory cells 

are merely distributed in the epithelium beneath the cuticle, 

opening to the exterior via individual pores, and the 

presence of pheromone-producing cells is inferred from 

female mounting and feeding behavior (e.g., Blaberus, 

Archimandrita, Byrsotria—Roth, 1969; Wendelken and 

Fig. 6.7 Scanning electron micrographs of the tergal gland of 

male Phyllodromica delospuertos (Blattellidae), in increasing 

detail. Top, tergite 7, middle, tergal gland, bottom, bristles of the 

gland. From Bohn (1999), courtesy of Horst Bohn, with permission 

from the journal Spixiana. 

considered to be the more anterior ones, because they 

draw the female forward, bringing her genitalia into 

closer alignment with those of the male (Roth, 1969). The 

Anaplectinae and Cryptocercidae have tergal modifications 

of unknown functional significance because they 

occur in unusual locations. In the former the tergal gland 

is on the supra-anal plate (Roth, 1969). In C. punctulatus 

the gland is located on the anterior part of the eighth tergite, 

completely concealed beneath the expanded seventh 

tergite (Farine et al., 1989). Because of its relatively inaccessible 

position, it is unlikely that it functions to elicit 

Fig. 6.8 Male tergite 7 of representative species of Phyllodromica 

(Blattellidae: Ectobiinae) showing two sets of tubular 

pouches underlying the tergal gland. The anterior pair of tubes 

(“t”) are thick and sometimes branched; the posterior pair of 

tubules (“tl”) are very thin and unbranched. The “tl” tubules of 

Phy. ignabolivari were lost during preparation and are indicated 

by dotted lines. From Bohn (1993), courtesy of Horst 

Bohn, and with permission from the Journal of Insect Systematics 

and Evolution ( Entomologica Scandinavica). 


Barth, 1985). In some blattellids the internal glandular 

apparatus is enormous. Blattella meridionalis has glands 

that form elongate sacs extending well into the next abdominal 

segment (Roth, 1985). In the panteli group of 

Phyllodromica the internal reservoirs consist of two pairs 

of long tubular pouches (Fig. 6.8). The anterior pair is 

thick, branched in some species, and open to the exterior 

via an open bowl or pocket. The posterior pair of tubules 

is very thin and unbranched, with small openings that lie 

behind the larger openings of the anterior glands (Bohn, 

1993). 

Functional Significance 

External pits, “bowls,” or depressions function as reservoirs 

for the tergal secretion oozing up from underlying 

glandular cells (Roth, 1969; Brossut and Roth, 1977; 

Sreng, 1979b). In some instances, drops of liquid can be 

seen forming at the opening of the gland as the female 

feeds (e.g., R. maderae—Roth and Barth, 1967). The secretion 

produced by the tergal glands is a mixture of 

short-range volatile and non-volatile fractions, the latter 

including protein, lipids, and carbohydrates (Brossut et 

al., 1975; Korchi et al., 1999). The best-studied, that of B. 

germanica, is a complex synergistic mixture of polysaccharides, 

17 amino acids, and lipids, including lecithin 

and cholesterol. Maltose, known from baiting studies to 

be a potent phagostimulant for the species, is one of the 

primary sugars (Kugimiya et al., 2003; Nojima et al., 

1999a, 1999b). There is little relationship between response 

to the secretion and sexual receptivity. Both sexes 

and all stages are attracted (Nojima et al., 1999b). Because 

tergal secretions exploit a female’s underlying motivation 

to feed, they can be classified as “sensory traps” (Eberhard, 

1996). They mimic stimuli that females have 

evolved, under natural selection, for use in other contexts. 

It is uncertain to what degree tergal secretions provide 

a nutritional boost to grazing females. The behavior is 

most often described as “licking” or “palpating,” but the 

action of the female’s mandibles and the manner in which 

she presses her mouthparts against the male’s gland indicate 

that she actually eats the secretion. The male typically 

lets her feed 3–7 sec before attempting to make genitalic 

connection (Roth and Willis, 1952a; Barth, 1964; Roth, 

1969). Females of Eurycotis floridana may graze for nearly 

a minute, longer than any other studied species (Barth, 

1968b). Feeding may also be “quite prolonged” in Periplaneta 

spp., with the female vigorously biting the tergite. 

The male gland in Rhyparobia maderae can be extensively 

scarred (Simon and Barth, 1977b), attesting to female enthusiasm 

for the fare. Roth (1967c) suggested that in 

species with very deep, well-developed tergal glands located 

near the base of the male’s wings, females may feed 

on tergal secretions during the entire period of copulation, 

that is, they may not rotate off the male’s back into 

the opposed position. The extent to which tergal glands 

provide females with a significant source of nourishment 

is in need of examination, particularly in species with 

large glandular reservoirs. In many insects with courtship 

feeding the food gift provides no significant nutritional 

benefit to the female (Vahed, 1998). The amount of secretion 

ingested by B. germanica does seem negligible. On 

the other hand a female may feed on the tergal secretion 

of the male 20 times in a half hour without resultant copulation 

(Table 6.2), and courtship activities can deplete 

the gland (Kugimiya et al., 2003). 

Blattella germanica is a good example of the concept 

that in species utilizing sensory traps, males are selected 

to exaggerate the attractiveness of the signal while minimizing 

its cost (Christy, 1995). The German cockroach 

has double pouches on the seventh and eighth tergites, 

with the ducts of underlying secretory cells leading to the 

lumen of the pouch (Roth, 1969). During courtship, the 

female feeds on the secretions in the cavities on the eighth 

tergite. After 2–5 sec, the male slightly extends his abdomen, 

causing the female to switch her feeding activities 

to the gland on the seventh tergite, triggering genitalic extension 

on the part of the male. The female can contact 

the tergal secretions with her palps, but the cuticular 

openings of the glands are too small to permit entry of the 

mandibles and allow a good bite. She plugs her paraglossae 

into the cavities and ingests the tiny amount of glandular 

material that sticks to them. The forced lingering as 

she repeatedly tries to access the secretions keeps her positioned 

long enough for a copulatory attempt on the part 

of the male (Nojima et al., 1999b). The tergal glands in B. 

germanica are akin to cookie jars that allow for the insertion 

of your fingers but not the entire hand. The design 

encourages continued female presence, but frugally dispenses 

what is presumably a costly male investment. 

Males of other species may take a more direct approach 

to “encouraging” females to maintain their position. In a 

number of Ischnoptera spp., the tergal gland is flanked by 

a pair of large, heavily sclerotized claws, each of which has 

four stout, articulated setae forming the “fingers.” When 

the female is feeding on the tergal gland she must place 

her head between these claws “and probably applies pressure 

to the articulated setae” (Roth, 1969, Figs. 47–53; 

Brossut and Roth, 1977, Figs. 18–19). These structures, 

however, are quite formidable for simple mechanoreceptors, 

and may function in restraining the female rather 

than for just signaling her presence. 

Because tergal secretions are sampled by the female 

prior to accepting a male or his sperm, they may provide 

a basis for evaluating his genetic quality, physiological 

condition (Kugimiya et al., 2003), or in some species, his 

98 COCKROACHES

Table 6.2. Summary of sexual behavior of 10 pairs of Blattella germanica observed for 30 min; from Roth and Willis (1952a), LMR’s first 

published study on cockroaches. 

Pair number 

Behavior of 

cockroaches 1 2 3 4 5 6 7 8 9 10 

Number of 

times male 

courted female 1 20 44 4 14 27 17 37 48 33 17 

Number of 

times female fed 

on tergal gland 2 10 19 1 0 2 9 10 9 20 3 

Time (sec) male 

in courtship 

position 679 1385 59 169 576 698 997 1106 916 576 

Copulation 

successful? — — — — — — — — — 

1 

Courting defined as the male elevating and holding his wings and tegmina at a 45 to 90 degree angle. 

2 

This figure also indicates the number of times the male tried to engage the female’s genitalia, which almost invariably occurs after she has fed on the 

tergal gland for several seconds. 

ability to provide a hearty postnuptial gift in the form of 

uric acid (discussed below). Oligosaccharides in the tergal 

secretion of B. germanica do vary individually and 

daily (unpublished data in Kugimiya et al., 2003). Perhaps 

repeated tasting by the female (Table 6.2), then, is an evaluation 

process. Alternatively, females may need to exceed 

a certain threshold of contact with or ingestion of the tergal 

secretion before accepting genitalic engagement (Gorton 

et al., 1983). Finally, she may simply be trying to maximize 

her nutritional intake. Repeated instances of a 

female applying her mouthparts to a male tergal gland 

but leaving without copulation is particularly prevalent 

in starved females (Roth, 1964b). Nojima et al. (1999a) 

suggested that tergal secretions may be indirect nutritional 

investment in progeny, but the nutritional value to 

the female and her offspring remains to be demonstrated. 

Roth and Willis (1952a) were the first to note that in B. 

germanica, a chalk-white secretion composed of uric acid 

oozes from male uricose glands (utriculi majores) and 

covers the spermatophore just before copulating pairs 

separate (Fig. 6.9). Subsequent surveys made evident that 

uricose glands are unique to a relatively small subset of 

Blattaria. Within the Blaberoidea, the glands are common 

in the Pseudophyllodromiinae, less frequent in the Blattellinae, 

and in the Blaberidae occur only in some Epilamprinae. 

They are absent in Blattoidea (Roth and Dateo, 

1965; Roth, 1967c). 

Several hypotheses addressing the functional significance 

of uric acid expulsion via uricose glands have been 

offered. Because uric acid is the characteristic end product 

of nitrogen metabolism in terrestrial insects (Cochran, 

1985), initially it was thought that mating served as 

an accessory means of excretion in these species (Roth 

and Dateo, 1964). The glands of males denied mating 

partners become tremendously swollen with uric acid 

(Roth and Willis, 1952a), like cows that need milking. 

These excessive accumulations can result in increased 

male mortality (Haydak, 1953; Roth and Dateo, 1965). 

Field observations of cockroaches seeking out and ingesting 

uric acid from bird and reptile droppings (Fig. 

5.2), however, weaken the excretion hypothesis. It would 

also be unusual for males of a species to have a waste elim- 

MALE INVESTMENT: URIC ACID 

Fig. 6.9 Scanning electron micrograph of the edge of an emptied 

spermatophore with adhering spherical urate granules of 

varying diameter (Blattella germanica). From Mullins and Keil 

(1980), courtesy of Donald Mullins, and with copyright permission 

from the journal Nature (www.nature.com/). 


Fig. 6.10 Comparison of total radiolabel content of Blattella 

germanica females and the oothecae they produced while feeding 

on either a dog food (25% crude protein) or a 5% protein 

diet; these females were mated to virgin males that had been simultaneously 

injected with 3 H leucine (a representative amino 

acid) and 14 C hypoxanthine (a purine converted to uric acid in 

vivo). Dog food fed-females and their oothecae contained 17% 

of the male contributed radiolabel. Those on the low-protein 

diet contained 63% of the radiolabel made available to them at 

mating. Values are mean SEM. a vs. b, p 0.005; c vs. d, p 

0.027; e vs. f, p 0.007 (Student’s t-test). From Mullins et al. 

(1992), courtesy of Donald Mullins and with permission from 

the Journal of Experimental Biology. 

ination system unavailable to females and juveniles. From 

the female perspective, it was suggested that a spermatophore 

slathered with an excretory product would be 

an unattractive meal, and prevent her from consuming it 

before the sperm moved into storage (Roth, 1967, 1970a). 

An alternative suggestion was that the uric acid may function 

as a mating plug that deters additional inseminations 

(Cornwell, 1968). In species such as Miriamrothschildia 

( Onychostylus) notulatus, Lophoblatta sp., Cariblatta 

minima, Amazonina sp., and Dendroblatta sobrina, so 

much uric acid is applied by males that the female genital 

segments gape open (Roth, 1967c). 

The most strongly supported hypothesis is that the uric 

acid transferred during mating acts as a nuptial gift. In B. 

germanica, radiolabeled uric acid can be traced from the 

male to the female, and subsequently to her oocytes; the 

transfer occurs more readily when the female is maintained 

on a low-nitrogen diet (Fig. 6.10). The urates are 

probably ingested by the female, along with the spermatophore, 

but it is possible that a small fraction may 

enter via her genital tract (Mullins and Keil, 1980). An 

analogous urate transfer and incorporation occurs in X. 

hamata. In this case, the female turns, post-copulation, 

and feeds on a urate-containing slurry produced and offered 

by the male (Schal and Bell, 1982). After copulation 

the male raises his wings, telescopes his abdomen, widens 

the genital chamber, exposes a white urate secretion, and 

directs it toward the female, who ingests it. Females feed 

for about 3.5 min. As in B. germanica, females on nitrogen-deficient 

diets transfer to their maturing oocytes 

more male-derived uric acid than do females on highprotein 

diets. The magnitude of the gift offered by males 

of these two species depends on a combination of male 

age, size, diet, and frequency of mating. The uricose 

glands of newly emerged male B. germanica contain little 

or no secretion; they become filled in one or two days 

(Roth and Dateo, 1964). The glands are nearly emptied at 

each copulation (Roth and Willis, 1952a). 

Male to female transfer of uric acid probably occurs in 

all cockroach species that possess male uricose glands. A 

recently mated female Blattella humbertiana was observed 

removing excess uric acid with her hind legs, then 

eating some of the material before it hardened (Graves, 

pers, comm. to LMR in Roth, 1967c). In three species of 

Latiblattella the male’s genitalia and posterior abdominal 

segments are covered with “chalky white secretion” after 

mating, and females of Lat. angustifrons have been observed 

applying their mouthparts to it after mating 

(Willis, 1970). 

Paternal Investment or Mating Effort? 

A nuptial gift can benefit a male in two ways. The gift can 

function as paternal investment, where transferred nutrients 

or defensive compounds increase the number or 

quality of resultant offspring, or it can function as mating 

effort, which increases the male’s fertilization success 

with respect to other males that mate with the same female 

(Eberhard, 1996). The hypotheses are not mutually 

exclusive, and there is debate on the distinction between 

them, centering mainly on the degree to which a donating 

male has genetic representation in the offspring that 

benefit from the gift. The latter is dependent on female 

sperm-use patterns, the length of her non-receptive period 

following mating, and the time delay until the female 

lays the eggs that profit from the male’s nutritional contribution 

(reviewed by Vahed, 1998). 

The incorporation of male-derived urates into oothecae 

of B. germanica suggests paternal investment, supported 

by three lines of evidence (Mullins et al., 1992). 

First, urate levels in eggs steadily decrease during development. 

This strongly suggests that the uric acid is metabolized 

during embryogenesis (Mullins and Keil, 1980), 

presumably via bacteroids transmitted transovarially by 

the female (e.g., Sacchi et al., 1998b, 2000). Second, 14 C 

radioactivity not attributable to 14 C urate is present in tissue 

extracts of oothecae (Mullins and Keil, 1980; Cochran 

and Mullins, 1982; Mullins et al., 1992). As pointed out by 

Mullins and Keil (1980), however, the 14 C radiolabel 

reflects pathways involving carbon atoms and not neces- 

100 COCKROACHES

sarily the path of nitrogen contained in urates. In subsequent 

work, however, Mullins et al. (1992) demonstrated 

that, third, 15 N from uric acid fed to females did find its 

way into the nitrogen pool of oothecae, and was incorporated 

into four different amino acids. The question 

nonetheless remains as to whether the uric acid derived 

from a particular male ends up in the offspring that he 

sires (Vahed, 1998). Female B. germanica expel the empty 

spermatophore with the adhering urates about 24 hr after 

mating, then consume them between 4 and 18 days 

later, depending on her nutritional status (Mullins and 

Keil, 1980). Females typically transfer 90% of the food reserves 

accumulated during the pre-oviposition period 

into the next ootheca (Kunkel, 1966). It seems reasonable 

to assume, then, that the majority of the uric acid transferred 

during a given copulation is incorporated into the 

eggs of the next reproductive bout, particularly in unsated 

females. Young females rarely mate more than once 

prior to their first ootheca (Cochran, 1979b), so during 

the first oviposition period a male can be reasonably certain 

that his nuptial gift will benefit his own offspring. Females 

may, however, mate between ovipositions. Paternity 

of subsequent oothecae is variable, but there is a 

tendency for first-male precedence (Fig. 6.6). The nuptial 

gifts of male consorts following the first male, then, may 

benefit some nymphs fathered by other males. 

Gwynne (1984) argued that uric acid donation should 

not be classified as paternal investment, because, as a 

waste product, uric acid is likely to be low in cost. Vahed 

(1998) countered that it is likely to be a true parental investment 

precisely because of the low cost. If a gift is 

cheap, just a small resultant benefit to offspring will 

maintain selection for the investment. Neither author appreciated 

the fact that males deplete their uricose glands 

with each copulation, and actively forage for uric acid by 

seeking it out in bird and reptile droppings. The degree to 

which this foraging activity entails a cost in predation risk 

and energetic expense is an additional consideration. 

Although a demonstration that male-derived nutrients 

are incorporated into eggs supports the paternal investment 

hypothesis, it does not necessarily rule out the 

mating effort hypothesis (Vahed, 1998). Because female 

cockroaches feed on male-provided urates after spermatophore 

transfer, the nuptial gift cannot influence 

overt mate choice. The possibility remains that after copulation, 

females may bias sperm use based on the size or 

quality of the urate gift. In many species, females preferentially 

use the sperm of males that provide the largest 

nuptial gifts (reviewed by Sakaluk, 2000). With four separate 

chambers for sperm storage (discussed below), female 

B. germanica certainly have potential for exercising 

choice. The existence of substantial variation in sperm 

precedence suggests that she may be doing so. 

MALE GENITALIA 

The genitalia of most male cockroaches are ornate, 

strongly asymmetrical, and differ, at times dramatically, 

among species. Because they are among the primary 

characters used in cockroach taxonomy, some beautifully 

detailed drawings are available, but we have little understanding 

as to the functional significance of most components. 

The genital sclerites are usually divided into the 

left, right, and median (also called ventral) phallomeres. 

These can be relatively simple and widely separated, or 

form groups of convoluted, well-muscled structures elaborately 

subdivided into movable rods, hooks, knobs, 

spines, lobes, brushes, flagellae, and other sclerotized 

processes (Fig. 6.11). 

Several male genital sclerites are associated with the 

process of intromission and insemination; these include 

“tools” for holding the female, positioning her, and orienting 

her genitalia to best achieve spermatophore transfer. 

In Blatta orientalis, for example, all five lobes of the 

left phallomere, together with the ventral phallomere, 

serve to stabilize the ovipositor valves of the female, while 

a sclerite of the right phallomere spreads the valves from 

the center so that the spermatophore can be inserted 

(Bao and Robinson, 1990). Nonetheless, phallomeres are 

nearly absent in some blaberids, suggesting that elaborate 

hardware is not always a requisite for successful copulation. 

Mate-Holding Devices 

Some male genital structures function as mate-holding 

devices, allowing him to stay physically attached to the female 

during copulation. If the female mounts the male 

prior to genitalic connection (type I mating behavior), 

the male has a greatly extensible, sclerotized hook (“titillator”), 

used to seize and pull down her crescentic sclerite 

and to maintain his grasp on her when she rotates off his 

back into the opposed position. After the pair is end to 

end the male inserts the genital phallomeres. In B. germanica 

a pair of lateral sclerites, the paraprocts, grip the 

ovipositor valves from each side, and parts of the right 

phallomere (cleft sclerite) hold the valves from the ventral 

side (Fig. 6.12). The location of the genital hook in 

cockroach males varies, and distinguishes the Pseudophyllodromiinae 

(hook on right—Fig. 6.11A) from the 

Blattellinae (hook on left—Fig. 6.11C). The hook is always 

on the right in the Blaberidae (Fig. 6.11D) (Roth, 

2003c). 

Besides maintaining his grasp during positional 

changes, there are two basic reasons why a male needs a 

secure connection to the female during copulation: male 

competition and female mobility. In several species of 


Fig. 6.11 Examples of variation in male genitalia. (A) Genitalia (dorsal) of Allacta australiensis 

(Blattellidae: Pseudophyllodromiinae). Accessory median phallomere is broad, with an apical 

brush-like modification (arrow). From Roth (1991d). (B) Subgenital plate and genitalia (dorsal) 

of Hemithyrsocera nathani (Blattellidae: Blattellinae). A huge, sclerotized, densely setose brushlike 

structure is found on the left side (arrow). From Roth (1995a). (C) Subgenital plate and genitalia 

(dorsal) of Parasigmoidella atypicalis (Blattellidae: Blattellinae). Note distally curved median 

phallomere with a pick-axe-like apex (arrow) and three-fingered “claw” on right. From Roth 

(1999b). (D) Highly reduced phallomeres on the extruded aedeagal membrane of Panesthia 

cribrata (Blaberidae: Panesthiine). From Walker and Rose (1998). Phallomeres are labeled according 

to McKittrick’s (1964) classification. (E) Extraordinarily complex genitalia (dorsal) of 

Homopteroidea nigra (Polyphagidae). From Roth (1995d). 

blaberids, rivals disturb or attack courting or mating 

males. Copulations may be broken off because of interference 

in N. cinerea (Ewing, 1972). In B. craniifer males 

assault copulating pairs by jumping on their backs and attacking 

their point of juncture. The interference may 

cause separation of the pair, but only if it occurs during 

the first few seconds after they assume the opposed position. 

The copulating male “shows no reluctance in fighting 

with the intruder,” and “the trio may careen about the 

mating chamber” (Wendelken and Barth, 1985, 1987). A 

tight grasp of the female is also required because the pair 

may travel during copulation. Pairs are usually quiescent 

unless disturbed, in which case they move away. It is invariably 

the female that is responsible for the locomotion, 

dragging the passive male along in her wake (Roth and 

Barth, 1967). She can move with astonishing speed, 

pulling the “furiously backpedaling” male behind her (Simon 

and Barth, 1977a). Blattella germanica (Roth and 

Willis, 1952a), Byr. fumigata (Barth, 1964), Ell. humerale 

( affine) (Pope, 1953), Latiblattella spp. (Willis, 1970), 

Parcoblatta fulvescens (Wendelken and Barth, 1971), and 

P. americana (Simon and Barth, 1977a) are among the 

species in which this behavior has been reported. It also 

occurs in G. portentosa, even though the male is much 

heavier than the female (Barth, 1968c). 

Intromittent Organs 

The need for a secure connection, then, may account for 

some of the claspers, hooks, and spines in the male’s 

genitalic assemblage but cannot explain the bewildering 

complexity (Fig. 6.11E) of many components. The similarity 

of some cockroach structures to those of other, 

better-studied insects, however, allows us in some cases 

to make inferences from genitalic design. In particular, 

brushes and slender, elongate spines, rods, and flagellae, 

especially those with modified tips, may be sexually selected 

structures that increase a copulating male’s fertil- 

102 COCKROACHES

ization success. This may be accomplished in one of three 

basic ways: via the manipulation of rival sperm, by the 

circumvention of female control of sperm use, or via internal 

courtship of the female (Eberhard, 1985; Simmons, 

2001). 

A number of intromittent structures in male cockroaches 

have been called a penis, pseudopenis, phallus, or 

pseudophallus. Although these structures may be associated 

with the ejaculatory duct or have the appearance of 

organs specialized for penetration, sperm is transferred 

indirectly in cockroaches, via a spermatophore. Penis-like 

organs therefore function in some capacity other than to 

convey sperm directly from the testes of the male to the 

sperm storage organs of the female. In P. americana the 

pseudopenis, a structure of the left phallomere, is characterized 

as having a blunt, hammer-like tip and a thin dark 

ridge along its length (Bodenstein, 1953). According to 

Gupta (1947) the expanded tip of the pseudopenis enters 

the female gonopore (entry to the common oviduct) during 

copulation, and rotates 90 degrees on its own axis. In 

some Blattellidae (including Blattella) a conical membranous 

lobe between the right and left phallomeres is considered 

a penis. It is a posterior continuation of the ejaculatory 

duct and projects into the female genital chamber 

during copulation. A free spine, or virga, extends through 

the membranous wall of the penis above the gonopore. 

Snodgrass (1937) noted that males insert the virga into 

the female’s spermathecal groove during copulation, and 

suggested that it functioned to guide the sperm of the 

copulating male to their storage destination. Because 

sperm remain in the spermatophore until after the pair 

disengages, however, the functional basis of the virga 

must be sought elsewhere. In Pseudophyllodromiinae, 

R3, a sclerite of the right phallomere, has an expanded anterior 

edge that is elongate, in some genera extraordinarily 

so. Most often it is curved and flat, but in Supella it is 

Fig. 6.12 Diagrammatic representation of the external genitalia of Blattella germanica during 

copulation. (A) Side view of the initial position, female superior. The hooked left phallomere is 

extended and inserted into the genital chamber of the female. (B) The insects in the end-to-end 

position, ventral view. The paraprocts are holding the ovipositor from each side and the cleft sclerite 

is holding it from the ventral side. The last sternite in both insects and the endophallus have 

been removed. After Khalifa (1950), with permission from the Royal Entomological Society. Labels 

of the various structures courtesy of K.-D. Klass. 


Fig. 6.13 Male Chorisoserrata jendeki (Pseudophyllodromiinae) 

(A) genitalia, (B) dorsal view of abdomen, and (C) ventral 

view of abdomen, demonstrating the genitalic filament, or 

whip, that projects from the abdomen. From Vidlička (2002), 

courtesy of the author and with permission from the journal 

Entomological Problems. 

flat and horseshoe shaped, and in Lophoblatta it forms a 

long whip-like structure (Fig. 113 in McKittrick, 1964). 

Male Chorisoserrata jendecki have a genitalic filament that 

dangles from the abdomen, like a tail (Fig. 6.13) (Vidlička, 

2002). Nahublattella, in the same subfamily, has a 

long whip as part of the left phallomere complex (Klass, 

1997). Loboptera (Bohn, 1991a), Neoloboptera, and Nondewittea 

(Roth, 1989b) (Blattellinae) have elongated filaments 

associated with the median phallomere complex. 

In males of the tortoise beetle Chelymorpha alternans, 

whips similar to these are threaded up the female’s spermathecal 

duct during the early stages of copulation, and 

the length of the whip is related to the probability of fathering 

offspring (Rodriguez et al., 2004). 

Sperm Removal 

At the conclusion of a successful copulation in cockroaches 

the transferred sperm are housed within a spermatophore 

in the female genital tract. The male is long 

gone before his gametes move to the female spermathecae, 

and is likely to have little direct influence on where, 

how, and if his sperm are stored. If his female consort is 

not a virgin, however, there is potential for a copulating 

male to increase his fertilization success by using genital 

appendages to move or remove the stored sperm of a rival. 

Male intromittent organs are known to extract stored 

sperm in one of three basic ways (Eberhard, 1996; Miller, 

1990). First, a genital structure may be inserted into or 

near a spermatheca and the ejaculate issued with enough 

force to flush out a rival’s sperm. This mechanism is unlikely 

in cockroaches since sperm transfer is indirect, via 

a spermatophore. Second, male genital appendages may 

be used to induce the female to discard the sperm of other 

males. When a female cockroach oviposits, eggs emerging 

from the oviduct pass over sensory hairs that trigger a 

contraction in the peripheral muscle layer of the spermathecal 

bulb and sperm are discharged to fertilize the 

egg (Roth and Willis, 1954b; Lawson and Thompson, 

1970). Copulating males may take advantage of this reflex 

by using genital armature to tickle the mechanoreceptors, 

causing the female to expel the sperm of rivals before the 

male deposits his own. Third, the male may directly remove 

rival sperm using backward-facing hooks, spines, 

barbs, or brushes at the tip of elongate appendages (e.g., 

Yokoi, 1990; Kamimura, 2000). These structures enter the 

spermatheca, then scrape out, scoop out, or snag and drag 

the sperm present. This is possible in cockroaches, as in 

several species genital sclerites have the appearance of organs 

used for sperm removal or displacement in other insect 

species; these include brushes (Fig. 6.11A) and hooks 

(Fig. 6.11C) at the tip of intromittent-type organs. 

Copulatory Courtship 

If a female cockroach mates with more than one male 

during her reproductive lifetime, the manner in which 

she subsequently handles the sperm received from each 

partner plays a key role in determining the paternity of 

her offspring. After a copulation is terminated and the 

male leaves, the fate of his gametes is primarily under female 

control as they move from the spermatophore to the 

spermatheca(e), while they are being stored, while traveling 

from the spermatheca to egg, and at the site of fertilization 

(Eberhard, 1994, 1996). Female control of sperm 

use and the resultant potential to bias paternity is called 

cryptic mate choice, so named because it occurs within 

the recesses of the female body and is difficult to observe 

or investigate directly (Thornhill, 1983). 

If female post-copulatory sperm-use decisions are 

cued on particular types of stimuli, it will favor the male 

to elaborate structures and behaviors that produce those 

stimuli (Eberhard, 1985, 1994, 1996, 2001). Complex 

genital sclerites, then, may function to increase a male’s 

fertilization success indirectly, via internal courtship of 

the female. Internal thrusting is known to have a stimulatory 

function in copulating animals (Eberhard, 1996), 

and has been noted in a few cockroach species; however, 

the behavior also may be associated with the deep insertion 

of the genitalia, the transfer of the spermatophore, or 

the direct removal of rival sperm. Males of B. fumigata 

often make rhythmic pumping motions during the first 

few moments of copulation (Barth, 1964). Likewise, abdominal 

contractions of male N. cinerea occur throughout 

copulation but are most frequent in the initial stages 

(Vidlička and Huckova, 1993). Late in copulation the 

104 COCKROACHES

male of Eub. posticus “raises up on his forelegs and makes 

rhythmic pushing movements of his abdomen in a pulsating 

fashion” (Wendelken and Barth, 1987). Diploptera 

punctata males move their abdomen from side to side just 

prior to releasing the female (Roth and Stay, 1961). Conversely, 

females of Parc. fulvescens assume an arched posture 

during copulation, and rhythmical movements were 

observed for which the female appeared responsible 

(Wendelken and Barth, 1971). In addition to internally 

stimulating the female with genital structures, males may 

sing, tap, rub, hit, kick, wave, lick, wet with secretions, 

bite, feed, rock, and shake females in attempting to influence 

cryptic choice decisions (Eberhard, 1996). The production 

of oral liquid during mating by male Parc. fulvescens 

was listed by Eberhard (1991) as a form of 

copulatory courtship. A repeating sequence of pronotal 

butting, abdominal wagging, and circling behavior has 

been observed in C. punctulatus after genital disengagement 

(Nalepa, 1988a) and has been interpreted by Eberhard 

(1991) as post-copulatory courtship. 

Reduction and Loss of Genitalic Structures 

The genital phallomeres of some blaberid cockroaches 

are lightly sclerotized, considerably reduced, or in some 

cases, altogether absent. The Panchlorinae are characterized 

by the absence of a genital hook, and if the remaining 

two phallomeres are present, they are markedly reduced 

(Roth, 1971b). Likewise, one or more phallomeres 

may be reduced or absent in many Panesthiinae (including 

Geoscapheini) (Fig. 6.11D) (Roth, 1977). Macropanesthia 

rhinoceros and M. heppleorum males completely 

lack a genital hook, and sclerites L1 and L2d 

are also missing. Some of the Australian soil-burrowing 

cockroaches exhibit intraspecific variation in the reduction 

of phallomeres (Walker and Rose, 1998). The occurrence 

of poorly developed male genitalia in cockroaches 

corresponds very well with copulatory behavior. A reduced 

or absent genital hook is strong evidence of type III 

mating behavior, that is, the male backs into the female to 

initiate mating (Roth, 1971b, 1977). 

Simple genital structure in males is predicted by the 

cryptic choice hypothesis if females are monandrous, because 

sexual selection by female choice is possible only if 

females make genitalic contact with more than one male 

(Eberhard, 1985, 1996). In monandrous females, the 

choice of sire is settled prior to copulation, via mechanisms 

such as premating courtship or male-male contests. 

The mating strategy in cockroaches with reduced 

genitalia is not known well enough to determine if that is 

the case here; however, one male is usually present in social 

groups of Panesthia. Panesthia cribrata typically lives 

in aggregations, often (29%) comprised of a single adult 

male, a number of adult females, and nymphs of various 

sizes (Rugg and Rose, 1984a). 

Additional correlates of reduced male genitalia in 

cockroaches also must be considered. Among the Panesthiinae 

species studied, the absence of an oothecal covering 

around the eggs is correlated with the absence or reduction 

of male genital structures (Walker and Rose, 

1998). All of the species for which we have information 

also exhibit a burrowing lifestyle, tunneling in soil, rotted 

wood, or rotted palms. How all these threads connect 

(burrowing lifestyle, mating system, copulatory behavior, 

male genital morphology, and absence of egg case) awaits 

further study. It is of interest (Chapter 9), however, that 

termites are monogamous (Nalepa and Jones, 1991) and 

that isopteran males are largely unencumbered by genitalia 

(Roonwal, 1970). Termites also live in burrows, mate 

by backing into each other, and except for Mastotermes, 

have lost the casing around their eggs. Species in the 

Cryptocercidae, the sister group of termites, live in burrows 

and are apparently monandrous, but male genitalia 

are not markedly reduced; they do, however, exhibit a 

number of paedomorphic characters (Klass, 1997). 

THE FEMALE PERSPECTIVE 

A variety of female traits can bias paternity, including the 

premature interruption of copulation and the acceptance 

or rejection of matings from additional males. Females 

may also accept a male for copulation but reject him as a 

father. This is possible because insemination and fertilization 

are uncoupled in space and time (Eberhard, 

1985), and because females have many opportunities to 

modify the probability that a given copulation will result 

in egg fertilization. There are at least 20 different mechanisms 

that can result in cryptic female choice (Eberhard, 

1994, 1996), many of which may apply to cockroaches. 

These include sperm transport to storage sites, sperm 

nourishment during storage, the ability to discharge or 

digest stored sperm, and the biased use of stored sperm to 

effect fertilization, particularly in females with multiple 

spermathecae. Sperm selection may even occur at the site 

of fertilization; Eberhard (1996) gives as an example Periplaneta, 

which has up to 100 micropyles for sperm entry 

at one end of the egg (Davey, 1965). After fertilization 

ovoviviparous females may abort the egg case. The multiplicity 

of female mechanisms reduces the likelihood 

that males will be able to evolve overall control of female 

reproductive processes, even if males try to prevent further 

matings via genital plugs, mate guarding, or induced 

unreceptivity (Eberhard, 1996). While there are no available 

studies that directly address cryptic choice in female 


cockroaches, we do have anatomical data from the taxonomic 

literature from which we can make some inferences. 

Here we summarize some of the relevant information 

in the hope that it may serve as a springboard for 

future investigation. 

Female Receptivity 

Female cockroaches have strong control of the courtship 

and mating process; there are several points in the behavioral 

sequence when she can terminate the transaction. In 

those cockroach species where females produce volatile 

pheromones, she may not call; if males produce the 

pheromones, she may not respond. Females may refuse to 

mount and feed on the tergites of a displaying male, but 

if she does, she may not allow genitalic engagement. If she 

does allow genitalic engagement, she may terminate copulation 

prematurely. A female’s attractiveness to potential 

mates and her response to sexual overtures from them 

may or may not be congruent (Brousse-Gaury, 1977). 

Males of Su. longipalpa, for example, begin courting females 

8 or 9 days after the female’s imaginal molt. Females 

of this age do not respond to male sexual displays nor do 

they mate. Female calling and sexual receptivity are initiated 

11 to 15 days after adult emergence. A lack of calling 

behavior in mature females, however, does not necessarily 

mean that they are unreceptive; 8% will mate if 

courted (Hales and Breed, 1983). 

Response to Courtship 

In most species newly emerged females require a period 

of maturation before they will accept mates. Virgin females 

of N. cinerea, R. maderae, and Byr. fumigata become 

receptive at an average of 4, 9, and 15 days, respectively 

(Roth and Barth, 1964). Eublaberus posticus females 

mate just after emergence, after their wings have expanded 

but before the cuticle has hardened (Roth, 

1968c). Jagrehnia madecassa (Sreng, 1993), Neostylopyga 

rhombifolia (Roth and Willis, 1956), and D. punctata 

(Roth and Willis, 1955a) females are receptive when they 

are freshly emerged, pale, and teneral. The latter have a 

narrow window of opportunity for copulation; most that 

are isolated for several days following emergence do not 

mate when they are eventually exposed to males (Stay and 

Roth, 1958). In N. cinerea, younger females require longer 

periods of courtship prior to copulation than do older 

ones (Moore and Moore, 2001). 

Females display their lack of receptivity to courting 

males in a variety of ways. A Parc. fulvescens female uninterested 

in mating decamps immediately upon contacting 

the male (Wendelken and Barth, 1971). Unreceptive 

blaberid females commonly flatten themselves against the 

substratum with their antennae tucked under their body 

(e.g., Byr. fumigata—Barth, 1964). Blaberus females will 

lower the pronotum or the entire body (Grillou, 1973), 

tilt the body down on the side facing the male, or kick at 

courting males (Wendelken and Barth, 1987). Some blattid 

females can be aggressively unreceptive, and escalate 

their belligerent behavior when courted by highly motivated 

males. Occasionally persistence pays off; females 

sometimes gradually shift to a less aggressive, more receptive 

pattern of behavior (Simon and Barth, 1977b). 

Aggression by males directed against unreceptive females 

is infrequent. Blaberus giganteus males occasionally bite 

an unreceptive female’s wings (Wendelken and Barth, 

1987), but forced copulation by males cannot occur in 

species where mating is dependent on female mounting 

and feeding behavior (Roth and Barth, 1964). 

Copulation Refusal 

Females often mount and feed on the tergal glands of 

courting males, but refuse to allow genitalic engagement. 

The nature of tergal secretions may be at least in part responsible; 

in the German cockroach the secretions smell 

like food and thus may lure hungry females regardless of 

their interest in mating. After mounting and feeding, a 

cooperative female orients her abdomen and opens her 

genital atrium to facilitate interaction with male genitalia 

(Roth and Willis, 1952a). Alignment of the two abdominal 

tips can require considerable female adjustment, particularly 

in species where she is larger than the male. Byrsotria 

fumigata females flex the abdominal tip forward 

ventrally so that genital connection can be made (Barth, 

1964) and Blab. craniifer females may partially dismount 

in an attempt to improve the orientation of the genitalia 

(Wendelken and Barth, 1987). Cooperative females also 

open wide to allow full genital access. In Eur. floridana the 

gape of a receptive female’s genital atrium is so impressive 

that the male can insert the entire tip of his abdomen 

(Barth, 1968b). Species in which the sexes back into each 

other also require female cooperation to copulate successfully. 

Panesthia cribrata females raise the tip of the abdomen 

and open the posterior plates (O’Neill et al., 1987). 

After the genitalia are engaged, there are three major 

points at which a pair may separate: during turning to the 

opposed position, a few seconds after turning, and during 

the first 15 min of copulation. The signal to assume 

the opposed position comes from the male. He moves 

slightly forward, and the female responds by rotating off 

his back. If the female initiates the turning, it invariably 

results in separation of the pair (Simon and Barth, 

1977a). After assuming the opposed position, brief genitalic 

connections of 4–7 sec are not uncommon in B. germanica 

(Roth and Willis, 1952a). Eublaberus posticus 

females frequently kick at the point of intersexual juncture 

with their metathoracic legs (Wendelken and Barth, 

106 COCKROACHES

1987). In 12% of copulations of D. punctata observed by 

Wyttenbach and Eisner (2001), the teneral female pushed 

at the male with her hind legs until he disengaged; in each 

case the female subsequently accepted a second male. Females 

of N. cinerea require a longer period of courtship 

prior to copulation if they can detect the chemical traces 

of former female consorts on a male (Harris and Moore, 

2005)—the cockroach equivalent of lipstick on his collar. 

After genitalic engagement, they can apparently determine 

if a male is depleted of sperm or seminal products 

because of those recent matings. After the first copulation 

“males are less adept at grasping the female,” and pairs often 

remained joined for only a few seconds or minutes; 

no spermatophore is transferred. The female pushes the 

male with her hind legs, forcing him to release her (Roth, 

1964b). Further evidence of female control of copulation 

in N. cinerea comes from transection experiments. When 

female genitalia were denervated males could not grasp 

the female properly and they stayed connected for only a 

few seconds (Roth, 1962). 

Copulatory Success 

Several studies report that male B. germanica have an 

abysmal record of successfully courting and copulating 

with females provided to them. Curtis et al. (2000) exposed 

each of 9 virgin males to serial batches of 2–10 virgin 

females throughout their lifetime (total of 341 females). 

Only 27 females were successfully inseminated. 

One-third of the males sired no offspring, and a further 

third inseminated just a single female. In a study of 55 virgin 

pairs by Nojima et al. (1999b), 84% of males courted 

females, 65% of the females responded by tergal feeding, 

but only 37% made the transition to copulation. Roth 

and Willis (1952a) did a detailed analysis of courtship and 

copulation in 10 pairs of German cockroaches (Table 

6.2). Males courted rather vigorously in most cases; male 

8, for example, courted the female 48 times in 30 min. 

Four females (pairs 3, 4, 5, 10) were nearly or completely 

unresponsive to male courtship, and 5 females responded 

by tergal feeding but refused to mate (pairs 2, 6–9). Just 

one of the 10 observed pairs successfully copulated. This 

puzzling lack of copulatory success has been noted in at 

least 2 other cockroach species. O’Neill et al. (1987) reported 

that in the majority of observed courtships, females 

of Pane. cribrata (Blaberidae) were not receptive. 

Males of P. americana (Blattidae) are rarely readily acceptable 

to the female (Gupta, 1947); only one in 20 attempted 

matings appeared successful in Rau’s (1940) 

study of the species. 

Female Loss of Receptivity 

Although female sexual receptivity is inhibited as a result 

of mating in all cockroach species studied (Barth, 1968a), 

the fine points of its physiological control are far from 

straightforward. Not only do details of regulation differ 

among species, but the various components of mating behavior 

are controlled in distinct ways within a species 

(Roth and Barth, 1964). “It is essential to be wary of generalization” 

(Grillou, 1973). Mechanical cues are of primary 

importance in examined cockroaches, but chemical 

influences cannot always be ruled out (Engelmann, 

1970). Interaction with male genitalia, the presence of the 

spermatophore in the female genital tract, and sperm or 

seminal fluid in the spermathecae have all been reported 

as mechanical cues influential in the initial or sustained 

loss of receptivity in cockroaches following mating (Roth 

and Stay, 1961; Roth, 1964b; Stay and Gelperin, 1966; 

Smith and Schal, 1990; Liang and Schal, 1994). The phenomenon 

is best studied in three cockroach species, the 

blattellids B. germanica and Su. longipalpa, and the blaberid 

N. cinerea. In the blattellids, one aspect of female receptivity, 

calling, is turned off by two successive mechanical 

cues provided by males during copulation. First, the 

insertion of a spermatophore results in the immediate 

cessation of calling. The behavior can be suppressed in 

experimental females by a spermatophore in the genital 

tract, by the insertion of a fake spermatophore, and by 

copulation with vasectomized males. The spermatophore 

effect, however, is transient. The presence of sperm or 

seminal fluids in the spermathecae is the stimulus that 

maintains the suppression of calling behavior in the first 

as well as the second ovarian cycles. The ventral nerve 

cord plays a crucial role in the transmission of the inhibitory 

signals (Smith and Schal, 1990; Liang and Schal, 

1994). Signals transferred via the nerve cord also decrease 

locomotor activity in females (Lin and Lee, 1998). 

The suppression of receptivity in N. cinerea following 

mating requires a single cue: mechanical stimulation 

caused by the insertion of the spermatophore into the 

bursa copulatrix (Roth, 1962, 1964b). The insertion of 

glass beads into the bursa results in the same loss of receptivity, 

manifested as a lack of a feeding response to 

male tergal displays. Spermatophore removal experiments 

indicate that female receptivity is lost immediately after 

the male reproductive product is firmly inserted into the 

bursa but prior to the migration of sperm into the spermatheca. 

Cutting the nerve cord above the last abdominal 

ganglion in N. cinerea renders the female “permanently” 

receptive. However, it is curious that the ventral 

nerve cord in most females must remain intact for two 

days for female receptivity to be inhibited. Vidlička and 

Huckova’s (1993) finding that female N. cinerea become 

unresponsive to male sex pheromone about 2 days after 

mating is consistent with the results of these transection 

studies. Roth (1970b) suggests the possibility that mating 

stimuli are transmitted rapidly to the last abdominal gan- 


glion but require a longer period to reach the brain, or 

that there is another source of stimulation in the genital 

region. If firmly inserted spermatophores are removed 

from mated females, about 15% will mate again (Roth, 

1964b). After copulation, females remain unreceptive until 

after partition, at which time most remate. The absence 

of sperm in the spermatheca does not influence the return 

of receptivity after the first oviposition (Roth, 1962, 

1964a, 1964b). 

Mating Plugs 

In cockroaches, the physical presence of a spermatophore 

in the genital tract of a female may play a dual role in preventing 

sperm transfer from other males. Besides acting 

as mechanical triggers in turning off female receptivity, 

they may also serve as short-term physical barriers to the 

placement of additional spermatophores. Copulating 

males typically deposit spermatophores directly over the 

spermathecal openings. If a female accepts an additional 

male and a second spermatophore is inserted, it is doubtful 

that the second male’s sperm could access female 

sperm storage organs. Additional spermatophores are 

usually improperly positioned (Roth, 1962; Graves, 1969). 

Spermatophore shape and its mechanism of attachment 

vary among cockroach taxonomic groups and some types 

are probably more refractory to dislodgment than others. 

In some blaberids the spermatophore has a dorsal groove 

that fits closely against the female genital papilla (Graves, 

1969). In blattellids with uricose glands, uric acid deposited 

on the spermatophore can fill the genital atrium 

of the female (Roth, 1967c). 

The spermatophore is discarded by the female after 

20–24 hr in P. americana (Jaiswal and Naidu, 1976), after 

2–3 days in Blatta orientalis (Roth and Willis, 1954b), after 

4–9 days in Eub. posticus (Roth, 1968c), by the 5th day 

in Blab. craniifer (Nutting, 1953b), by the 6th day in D. 

punctata (Engelmann, 1960), and after 6–13 days in R. 

maderae (Roth, 1964b). Young females of N. cinerea extrude 

the spermatophore after 5 or 6 days, but older females 

may retain it for over a month (Roth, 1964b). The 

mechanism by which cockroach females eject the spermatophore 

is not altogether clear. In B. germanica, the 

spermatophore remains in place about 12 hr and then 

shrinks; the shriveled remains may adhere to the female 

for several days (Roth and Willis, 1952a). Jaiswal and 

Naidu (1976) indicate that shrinkage of the outermost 

layer also causes spermatophore separation in P. americana, 

but Hughes and Davey (1969) thought that it disintegrated 

as a result of exposure to spermathecal secretions. 

Disintegration of the spermatophore is also 

reported in Blab. craniifer (Hohmann et al., 1978). A secretion 

from the spermathecal glands apparently facilitates 

spermathecal extrusion in four examined Blaberidae 

(D. punctata, R. maderae, N. cinerea, Byr. fumigata). 

The secretion is under the control of the corpora allata, 

and loosens the spermatophore by softening the material 

covering it (reviewed by Roth, 1970b). Nonetheless, a few 

experimental females of R. maderae were able to extrude 

their spermatophores despite surgical removal of the 

spermathecal glands (Engelmann, 1957). 

Mechanical Stimulation and “Imposed Monogamy” 

Roth’s (1964b) demonstration that the suppression of female 

receptivity results from the physical insertion of the 

spermatophore into the bursa in N. cinerea has been interpreted 

as evidence that males force monandry on females 

during their first reproductive cycle. The bursa and 

the brood sac are in close physical proximity within the 

female genital tract. This serves as the basis for the 

argument that males are co-opting the physiological 

mechanism evolved to suppress female receptivity during 

pregnancy, and so females are precluded from evolving 

countermeasures to this manipulation (Harris and 

Moore, 2004; Montrose et al., 2004). Several points must 

be carefully considered before accepting this interpretation. 

First, while the brood sac is spatially proximate to the 

genital papilla on which the spermatophore is secured, 

there is no evidence that the two structures share a mechanism 

for suppressing female receptivity. The highly distensible 

brood sac is situated at the anterior end of the 

vestibulum. It is separated from the genital papilla by the 

laterosternal shelf (McKittrick, 1965) (Fig. 6.14A). When 

the female is incubating an ootheca, the genital papilla is 

forced to stretch as the egg case projects into the vestibulum 

(Fig. 6.14B). Nonetheless, engaging the mechanoreceptors 

in the brood sac of a virgin has little to no effect 

on her receptivity. When glass beads were inserted into 

the brood sac without applying pressure to the bursa, 

72% of virgins subsequently mated. Some physiological 

change occurs after ovulation that makes females responsive 

to inhibitory stimuli from the stretched brood sac 

(Roth, 1964b, p. 925). The loss of receptivity after the first 

copulation of her adult life, and the loss of receptivity in 

response to an ootheca stretching the brood sac, then, do 

not have a shared control mechanism. 

Second, the imposed monogamy scenario is predicated 

on the assumption that multiple copulations within the 

first reproductive cycle confer benefits on female N. cinera. 

In many insects, females profit from multiple matings 

because they can increase fitness via increased egg production 

and fertility (Arnqvist and Nilsson, 2000). A 

male, on the other hand, benefits by rendering females 

sexually unreceptive after mating, thus increasing the 

probability that his sperm will fertilize the majority of 

the female’s eggs (Cordero, 1995; Eberhard, 1996; Gillott, 

108 COCKROACHES

Fig. 6.14 (A) Sagittal section of the female genitalia of Gromphadorhina portentosa (Blaberidae). 

(B) Diagrammatic sagittal section of blaberid female genitalia with ootheca in brood sac. From 

McKittrick (1964). 

2003). If multiple matings do increase female fitness, it 

follows that the control of female sexual receptivity is a 

source of conflict between the sexes, and females are expected 

to evolve resistance to the stimuli males use to induce 

receptivity loss (Arnqvist and Nilsson, 2000). That 

does not appear to be the case in N. cinerea. Copulation 

is known to confer numerous fitness benefits on female 

cockroaches (discussed below), but within the framework 

of cyclic receptivity typical of N. cinerea there is currently 

no evidence that more than one mate within the first 

reproductive cycle is advantageous. Moreover, morphological 

and experimental evidence suggests that spermatophore 

placement and therefore loss of receptivity in 

N. cinerea is likely under female control, suggesting that 

there is no conflict of reproductive interest between the 

sexes on this issue. Not only do females have morphological 

features specialized for proper spermatophore placement 

and retention, these features are regulated by her 

nervous system. Receptivity in N. cinerea is suppressed 

only if the spermatophore is firmly placed and properly 

positioned (Roth, 1964b). While in some blaberids a large 

amount of glue-like secretion cements the spermatophore 

into place, in Nauphoeta and several related genera 

the bursa is largely responsible for spermatophore retention 

(Graves, 1969). The bursa is deep, is extensively 

membranous, and almost completely wraps around the 

correspondingly elongated spermatophore. If the nerve 

cords are severed prior to mating in female R. maderae, 

another species with a deep, membranous bursa, 70% of 

males were not able to insert the spermatophore properly. 

They were placed elsewhere in the genital atrium or 

dropped by the male without being transferred. In many 

cases the male had pierced the wall of the brood sac and 

the spermatophore was in the female’s body cavity. “It 

seems the female takes an active role in the proper positioning 

of the spermatophore in the bursa copulatrix, and 

an intact nerve cord is needed for proper muscular movements 

of the female genitalia” (Roth and Stay, 1962a). 

Loss of Receptivity during Gestation 

Pregnant blaberid females typically do not respond to 

courting males. The physical presence of an ootheca in 

the brood sac inhibits mating behavior, and its removal 

leads to the return of receptivity (N. cinerea, Byr. fumigata) 

(Roth, 1962, 1964b; Grillou, 1973). The suppression 

of receptivity appears to be the direct result of sensory 


stimulation via mechanoreceptors that are abundant 

within the brood sac (Brousse-Gaury, 1971a, 1971b; 

Roth, 1973b; Greenberg and Stay, 1974). Internal gestation 

of eggs, then, leads to potentially large differences 

between oviparous and ovoviviparous species in the sexual 

availability of females (Wendelken and Barth, 1987). 

Live-bearing females are removed from the mating pool 

for extended periods of time; gestation lasts 35–50 days 

in N. cinerea (Roth, 1964a), 51 days in R. maderae (Roth, 

1964b), and 55–65 days in Blab. craniifer (Grillou, 1973). 

Blattella germanica, a species that externally carries the 

ootheca for about 21 days before the young hatch (Roth 

and Stay, 1962c), is intermediate. Oviparous females that 

drop their oothecae shortly after their formation lack the 

lengthy gestation periods of ovoviviparous cockroaches 

(Chapter 7) and so have relatively high rates of “recidivist 

receptivity” (Wendelken and Barth, 1987). Potentially, 

then, these females mate more frequently and presumably 

with a greater number of males. 

Secondary Effects of Copulation 

The primary role of copulation is egg fertilization, but a 

variety of secondary effects also occur. In cockroaches 

these include the suppression of female receptivity, but 

also diverse processes that facilitate female reproduction, 

such as the acceleration of oocyte growth, the prevention 

of oocyte degeneration, an increase in the number of 

oocytes matured and oviposited, the appropriate construction 

of the egg case, and, in ovoviviparous species, its 

proper retraction. The degree to which mating influences 

these processes as well as the details of their physiological 

control vary among studied species (Griffiths and Tauber, 

1942a; Wharton and Wharton, 1957; Roth and Stay, 1961, 

1962a, 1962c; Engelmann, 1970; Roth, 1970b; Adiyodi 

and Adiyodi, 1974; Hales and Breed, 1983; Goudey-Perriere 

et al., 1989). These secondary effects clearly promote 

female reproductive fitness, but are also considered 

beneficial to the male because they increase the likelihood 

that his sperm will be used by the female to sire her eggs 

(reviewed by Cordero, 1995; Gillott, 2003). 

Mating has been shown to stimulate oocyte maturation 

in all cockroach species studied to date (Holbrook et 

al., 2000b), but the instigating stimuli differ. The physical 

presence of the spermatophore, stimulation from male 

genitalia, mechanical pressure from a filled spermatheca, 

and the chemical presence of the spermatophore all have 

varying degrees of influence on female reproductive 

processes. The action of these stimuli also may be moderated, 

sometimes strongly, by nutritional and social factors. 

The mechanical stimulation caused by the firm insertion 

of the spermatophore in N. cinerea not only 

suppresses female receptivity, but is also responsible for 

stimulating oocyte development and for ensuring the 

normal formation and retraction of the ootheca during 

the first reproductive cycle (Roth, 1964b). The physical 

presence of the spermatophore has been similarly 

demonstrated to be sufficient stimulus for accelerating 

oocyte maturation in oviparous Su. longipalpa; an artificial 

spermatophore is a reasonable substitute (Schal et 

al., 1997). Diploptera punctata females are dependent on 

spermatophore insertion for rapid development of their 

oocytes. However, the act of mating alone, without passage 

of a spermatophore, may be sufficient for oocyte 

maturation in some females. The physical stimulus of the 

spermatophore together with the action of the male genitalia 

appear to produce maximum reproductive effects 

(Roth and Stay, 1961). The acceleration of oocyte growth 

that occurs after mating in P. americana can be prevented 

by removing the spermatophore prior to the movement 

of sperm into the spermatheca, or by mating the female 

to males whose spermatophores are of normal size and 

shape but lack sperm. Pipa (1985) concluded that the 

stimulus for oocyte growth in this species originates from 

the deposition of sperm or other seminal products into 

the spermatheca. The proper formation and retraction 

of the ootheca into the brood sac in N. cinerea (Roth, 

1964b) and Pyc. indicus is dependent on the presence of 

sperm in the spermatheca. After spermatheca removal, 

severance of spermathecal nerves, or mating with castrated 

males, females produced abnormal egg cases or 

scattered the eggs about (Stay and Gelperin, 1966). 

Male accessory glands typically contain a variety of 

bioactive molecules that, when transferred to the female 

during mating, influence her reproductive processes 

(Gillott, 2003). The spermatophore of Blab. craniifer is 

richly invested with enzymes whose activities change during 

the three days subsequent to mating; the longer the 

spermatophore remains in place (from 0–24 hr), the 

sooner oviposition occurs. Acetone extracts of the spermatophore 

topically applied to the female induce the 

same increases in vitellogenesis as do juvenile hormone 

mimics. Nonetheless, the physical presence of the spermatophore 

is also required for the full expression of reproductive 

benefits, and both mechanoreceptors and 

chemoreceptors are found in the bursa (Brousse-Gaury 

and Goudey-Perriere, 1983; Perriere and Goudey-Perriere, 

1988; Goudey-Perriere et al., 1989). 

In many cockroach species the female either internally 

digests and incorporates, or removes and ingests the spermatophore 

sometime after it is transferred to her (Engelmann, 

1970). However, there is currently little evidence 

that spermatophores are of nutritional value, aside from 

the uric acid that covers them in some species. Mullins et 

al. (1992) injected 3 H leucine into male B. germanica. The 

males transferred it to females during mating, who sub- 

110 COCKROACHES

sequently incorporated it into their oothecae. The source 

of the leucine-derived materials is unknown, but the authors 

suggested that it may have originated from the spermatophore 

or seminal fluids. 

Spermathecae 

Our understanding of the functional anatomy of the female 

cockroach reproductive tract in relation to cryptic 

mate choice languishes behind that of some other insect 

groups. The shape, number, elasticity, duct length, coiling 

pattern, musculature, presence of valves or sphincters, 

and chemical milieu of spermathecae play a strong role in 

sperm selection by females (Eberhard, 1996). Multiple 

sperm storage sites are particularly important in allowing 

females to cache and use the ejaculates of different 

males selectively (Ward, 1993; Hellriegel and Ward, 

1998). Sperm storage organs in cockroaches have not received 

much consideration since McKittrick (1964), who 

demonstrated a great deal of variety in the form, number, 

and arrangement of spermathecae (Fig. 6.15). In Cryptocercus 

the spermatheca is forked, with the branches terminally 

expanded; the single spermathecal opening lies 

in the roof of the genital chamber. The spermatheca of 

Lamproblatta has a wide, sclerotized basal portion and a 

slender forked distal region. Within the Polyphagidae, 

Arenivaga has a single, unbranched spermatheca, but 

Polyphaga has a small tubular branch coming off about 

halfway up the main duct. In the Blattellidae the spermathecal 

opening is shifted to a more anterior position 

on the roof of the genital chamber, far in advance of the 

base of the ovipositor. Some species of Anaplecta have, in 

addition, a pair of secondary spermathecae that open separately 

on the tip of a small membranous bulge, the genital 

papilla, that lies at the anterior end of the floor of the 

genital chamber (Fig. 6.15F). The cockroaches of this 

genus thus have either one or three spermathecae. The 

Pseudophyllodromiinae, Blattellinae, Ectobiinae, Nyctiborinae, 

and Blaberidae have secondary spermathecae 

only. The spermathecal pores in these may be widely 

spaced (Fig 6.15G—Pseudophyllodromiinae except Supella) 

or more closely situated within a spermathecal 

groove (Fig 6.15H—Supella, Pseudomops), thought by 

Snodgrass (1937) to function as a sperm conduit. One 

pair of spermathecae, each with a separate opening, is 

typically present in Pseudophyllodromiinae, but the Blattellinae 

may have two (Fig. 6.15I) or more pairs, each with 

a separate opening. Xestoblatta festae averages 10 or 11 

spermathecal branches, but these converge into just two 

exterior openings (Fig. 6.16K). Nyctibora sp. (Fig. 6.15J) 

and Paratropes mexicana have three pairs of spermathecae. 

All Blaberidae have a single pair of spermathecae that 

open on the genital papilla or directly into the common 

oviduct; in most species they are accompanied by a conspicuous 

pair of spermathecal glands (McKittrick, 1964). 

Spermathecal Glands 

Initially, the energy necessary for sperm maintenance and 

motility is provided in the semen. The seminal fluid of P. 

americana contains small amounts of protein, substantial 

glycogen, and some glucose, phospholipid, and other 

PAS-positive substances (Vijayalekshmi and Adiyodi, 

1973). Females are presumably responsible for fueling the 

long-term metabolic needs of sperm, as well as for creating 

a favorable environment for extended storage. In Periplaneta, 

for example, a female mated during her first preoviposition 

period can produce fertile eggs for 346 days 

subsequent to her first ootheca (Griffiths and Tauber, 

1942a). Parcoblatta fulvescens females can produce more 

than 30 oothecae without remating (Cochran, 1986a). It 

is possible, however, that at times stored sperm are neglected, 

digested, or destroyed; Breland et al. (1968) noted 

that the sperm in cockroach spermatheca are sometimes 

degenerated. 

Spermathecal walls are typically glandular, a trait functionally 

associated with providing for the maintenance 

requirements of the enclosed sperm. In some species the 

storage and secretory functions are largely separated via 

the development of one or more spermathecal glands 

(Gillott, 1983). Because cockroach spermathecae are also 

secretory, however, it has been difficult to make a distinction 

between spermathecae and spermathecal glands 

without direct observation of the location of stored 

sperm. An example is P. americana, whose spermatheca 

has two branches, both of which are muscular and secretory. 

The first spermatheca (“A” of Lawson and Thompson, 

1970) is an S-shaped capsular branch that terminates 

in a large swelling lined with a dense and deeply pigmented 

cuticular intima. It has a thick, underlying muscular 

layer and a smooth surface facing the lumen. Spermatheca 

“B” is a long, slender, tightly coiled branch with 

a thinner lining and strongly rugose inner surface. Secretory 

cells with collection centers fed by microvilli are far 

more numerous in the former than in the latter. The two 

spermathecae join basally to form a common duct. For 

many years, the slender, coiled branch was thought to be 

a spermathecal gland, until sperm were found in both 

branches following copulation (Marks and Lawson, 1962; 

Lawson and Thompson, 1970). Lawson thought that “B” 

served as a secondary storage reservoir for sperm. Hughes 

and Davey (1969) noted that the tubular branch seemed 

to release sperm more slowly than the capsular branch, or 

only after the capsular branch had finished discharging 

them. If so, sperm from the capsular branch may fertilize 

the majority of the female’s eggs, and a multiply mated female 

may bias paternity via differential sperm storage. 


112 COCKROACHES 

Fig. 6.15 Schematic of the number and position of spermathecae and spermathecal openings in 

representative cockroaches. (A) Blattinae, Polyzosteriinae; (B) Lamproblatta; (C) Cryptocercus; 

(D) Polyphaga (left), Arenivaga (right); (E) Anaplecta sp. A, B; (F) Anaplecta sp. C; (G) Pseudophyllodromiinae 

(except Supella); (H) Supella, Pseudomops; (I) Ectobiinae, Blattellinae (except 

Pseudomops, Xestoblatta); (J) Nyctibora; (K) Blaberidae. Area above the dashed line represents the 

dorsal wall of the genital chamber, area below the dashed line represents the ventral wall of the 

genital chamber. Shaded portions of the spermathecae are sclerotized areas. (A) to (E) have primary 

spermathecae only; (F) has both primary and secondary spermathecae; (G) to (K) have secondary 

spermathecae only. After Klass (1995), from data in McKittrick (1964), with permission 

of K.-D. Klass.

In those cockroaches that apparently possess both 

spermathecae and spermathecal glands, ambiguity as to 

whether all branches function in sperm storage has implications 

for species in the Blaberidae. Based on morphological 

observations, most species in this family have 

been described as having a pair of spermathecae and a 

pair of spermathecal glands, some of them quite elaborate 

(McKittrick, 1964). In R. maderae, for example (Fig. 

6.17), the glands are large, slender, highly branched, and 

open posterior to the openings of the spermathecae (van 

Wyk, 1952). Spermathecal glands in Diploptera entwine 

each spermatheca, and are “constantly filled with an intensely 

basophilic secretion” (Hagan, 1941). Marks and 

Lawson (1962), however, reported four paired spermathecae 

in Blab. craniifer, with the posterior member of each 

pair coiled, slender, and unbranched, and the anterior 

member sparsely branched. A functional analysis of these 

organs is necessary given their potentially influential role 

in sperm handling by the female. Spermathecal glands are 

thought to stimulate spermatozoa to enter the spermathecae 

(Khalifa, 1950), activate sperm, provide “lubrication” 

(van Wyk, 1952), and facilitate the extrusion of the 

spermatophore after mating (Engelmann, 1959, 1960). 

Spermathecal Shape 

Two “basic” spermathecal shapes are represented in cockroaches: 

the tubular form, with little difference in width 

between the duct and the spermatheca proper ( ampulla), 

and the capitate form, shaped like a lollipop. Shape 

varies widely across cockroach species and sometimes 

within a species. In Agmoblatta thaxteri each spermatheca 

has a double terminal bulb, like a figure 8 (Gurney and 

Roth, 1966). The genus Tryonicus can be inter- and intraspecifically 

polymorphic (Fig. 6.18) (Roth, 1987b); 

however, some apparent variation in spermathecal shape 

may be due to the amount of ejaculate stored or to the 

preservation of specimens at different stages of muscular 

activity. Both the ampulla and ducts are surrounded by a 

sheath of profusely innervated striated muscle (Gupta 

and Smith, 1969). The sheath is best developed at the 

base, where it consists mainly of circular fibers and functions 

as a sphincter in opening and closing the entry (van 

Wyk, 1952). 

It has been suggested that spermathecal shape can pre- 

Fig. 6.16 Morphological variation in cockroach spermathecae 

(A) Arenivaga bolliana; (B) Hypercompsa fieberi; (C) Neoblattella 

sp.; (D) Plecoptera sp.; (E) Miriamrothschildia notulatus; 

(F) Pseudomops septentrionalis; (G) Parcoblatta virginica; (H) 

Blattella germanica; (I) Ectobius pallidus; (J) Loboptera decipiens; 

(K) Xestoblatta festae. From McKittrick (1964) and Gurney 

and Roth (1966). 

Fig. 6.17 Drawing of the anterior view of the female genitalia 

of Rhyparobia maderae, showing the tubular spermathecae 

(spth, shaded gray) and extensive, branched spermathecal 

gland (sp gl). Slightly modified from McKittrick (1964). 


Fig. 6.18 Inter- and intraspecific variation in spermathecae of 

cockroaches in the genus Tryonicus (Blattidae: Tryonicinae). 

(A) Tryonicus parvus; large, bulbous reservoir arising preapically 

from a convoluted duct. (B) Tryonicicus angusta; reservoir 

spherical, sclerotized at one end and club-shaped on the other. 

(C) Tryonicus sp. 1; large spermathecal duct is same diameter 

as the spermathecal branch beyond the point of insertion of 

main reservoir. (D) Tryonicus monteithi from five locations in 

Queensland, Australia. After Roth (1987b). Scale bar is 0.5 mm 

in all cases. 

dict sperm use patterns (Walker, 1980), but the functional 

significance of spermathecal shape is complex (Otronen, 

1997) and not yet clear (Ridley, 1989). Large, globular 

ampullae may be associated with sperm mixing. Long 

tubular spermathecae may promote the layering of ejaculates, 

enhancing the “last in, first out” pattern of sperm 

precedence, or may serve as “sperm traps”to imprison the 

sperm of less favored males. Spermatozoa of R. maderae 

are apparently stored chiefly in the distal portion of the 

female’s tubular spermatheca. The proximal portion is 

filled with a granular secretion, which, according to van 

Wyk (1952), probably serves as food for the sperm. 

Multiple Storage Sites 

Most examined cockroaches have just one or two spermathecal 

lobes. The Blattellidae are extraordinary, however, 

in that some species have two, others, including 

Blattella, have four, and in some, the spermathecae look 

like a fistful of balloons (Fig. 6.16J). Each spermatheca 

may have its own opening (i.e., multiple spermathecae) 

(Nyctibora—Fig. 6.15J), or multiple branches may share 

a common orifice. In the latter case, the ducts may be arborescent 

(Fig. 6.16J), or branch from a single point (Fig. 

6.16K). 

Multiple storage sites offer potential for allowing a female 

to separate the sperm of different males spatially, 

giving her greater scope for choosing among potential 

sires and for postponing mate choice until oviposition. 

The bias can take the form of differential transport to 

storage sites, biased sperm survival in different spermathecal 

lobes, or differential transport from storage to the 

site of fertilization. Multiple spermathecae may also prevent 

male genitalic structures from accessing previously 

stored sperm, and allow specialization for more than one 

function, such as long- versus short-term storage (Eberhard, 

1996; Otronen et al., 1997; Hellriegel and Ward, 

1998; Pitnick et al., 1999). It is known, for example, that 

in the fly Dryomyza anilis, sperm movements in and out 

of individual spermathecae occur independently (Otronen, 

1997). Differential sperm storage is also known in 

the fly Scatophaga stercoria, and is mediated by female 

muscular activity (Hellriegel and Bernasconi, 2000). A 

detailed examination of the fates of different ejaculates 

within blattellid cockroaches is clearly indicated. The 

only relevant information known to us is from B. germanica. 

When the spermatophore is transferred to the female, 

the two sperm sac openings align directly with two 

of the spermathecal pores (Khalifa, 1950); nonetheless, 

sperm can be found in all four spermathecae of mated females 

(van Wyk, 1952; Marks and Lawson, 1962). Cochran’s 

(1979b) study of sperm precedence in the species 

suggests that selective use of sperm may be possible in 

multiply mated females (Fig. 6.6). 

SEXUAL CONFLICT OVER SPERM USE 

Male and female reproductive interests do not always coincide, 

and the conflict may be evident in their genital 

morphology.“Disagreement” over the removal or repositioning 

of stored sperm can select for male genitalia better 

designed to penetrate the female’s sperm storage organs, 

as well as female organs that are more resistant to 

male intrusion (Eberhard, 1985, 1996; Chapman et al., 

2003). There is a potential example of such antagonistic 

co-evolution among cockroaches in the Moroccan and 

Spanish species of Loboptera (Blattellinae) studied by 

Horst Bohn (1991a, 1991b). As noted above, males have a 

genital whip as part of the left phallomere complex. Females 

have spermathecae that are multiply lobed with 

long, convoluted ducts and as many as 10 branches on 

each side (L. glandulifera). In some species, the length of 

spermathecal ducts appears correlated with whip length 

in the male (Fig. 6.19), suggesting that as the female receptacle 

elongates, so does the adaptive value of a long 

whip in potential sires (and vice versa). Some males additionally 

have a sclerite densely covered with bristles, or 

membranes covered with long, narrow, hair-like scales in 

the vicinity of the intromittent organ (also occurring in 

other genera—Fig. 6.11B). In some Loboptera species the 

whip itself is covered in small bristles (L. delafrontera) or 

is densely hairy (L. juergeni). Spermathecae appear to 

have valves, sphincters, or other adaptations that serve to 

control sperm movement or to interact with male intromittent 

organs. Ducts can have accordion-like walls (L. 

truncata, L. cuneilobata), or a series of irregular swellings, 

114 COCKROACHES

Fig. 6.19 Spermathecae of female Loboptera (Blattellidae: Blattellinae) 

and corresponding genitalic structure in male. (A) 

Multi-branched spermathecae of L. decipiens nevadensis; (B) 

whip in male of the same species; (C) multi-branched spermathecae 

of L. barbarae (phase contrast); (D) whip in male of 

the same species. From Bohn (1991b), courtesy of Horst Bohn, 

and with permission from the Journal of Insect Systematics 

and Evolution ( Entomologica Scandinavica). 

giving them the appearance of a string of pearls (L. minor 

minor). Multiple reversals in the coiling direction of long 

thin, spermathecal ducts are common in the genus. Terminal 

ampullae may be globular, club shaped, or the same 

width as the spermathecal duct; branch points of ducts 

may be widely separated or originate from a single point. 

The morphological evidence for co-evolution of genital 

structures in male and female Loboptera is compelling; 

nonetheless, sexual biology and behavior in the genus are 

largely unknown. 

OPPORTUNITIES 

The literature to date suggests the taxa with the most 

promise for potentially productive studies of sexual selection 

occur within the Blattellidae, the largest but least 

known family of cockroaches. Males in this family variably 

possess diverse complex intromittent genital structures, 

elaborate tergal glands, uricose glands, and the 

most variable testes of examined species (Ph.D. thesis by 

E.R. Quiaoit, cited by Roth, 1970a). Females can have 

multiple spermathecae; furthermore, their reproduction 

can be closely tied to food availability, as they invest a high 

proportion of their bodily reserves into each reproductive 

event. The existence of these elaborate morphological 

structures, together with both prenuptial feeding via tergal 

glands and postnuptial feeding via uricose glands may 

be red flags signaling that male and female reproductive 

interests do not coincide. The potential for reproductive 

conflict is great when males provide nuptial gifts, because 

females are selected to obtain an optimal supply of nutrients, 

while males are selected for those traits that assure 

she uses his sperm (Thornhill and Alcock, 1983). The 

possession of morphologically complex, multiple spermathecae 

in females and a variety of intromittent-type 

structures in males suggest that control of sperm use in 

some blattellids may be an evolutionary chess game 

played out inside the female body during and after copulation. 

Blattellids as well as other cockroach taxa, then, are 

potentially rich sources of research material for a wide 

range of studies on insect mating strategies. Can the 

number of spermathecae or their structure be correlated 

with the morphology of any of the “blades” on the male’s 

Swiss army knife? Do elaborate spermathecae occur only 

in species with male uricose glands? Do complex male 

genital structures influence female sperm use, and if so, 

how do they do it? Does the quantity or composition of 

tergal secretion influence female choice? Are complex tergal 

glands and the possession of uricose glands correlated? 

Does the amount of uric acid transferred after copulation 

influence female sperm acceptance and use? It is 

clear that the scope of research needs to be expanded beyond 

the domestic pets and pests typically kept in laboratories, 

with an increased emphasis on bringing field and 

laboratory work into closer alignment. Even so, the study 

of sexual selection in cockroaches is in its early stages, despite 

the opportunities offered by even the most easily obtained 

and studied species. What is the function of giant 

sperm in Periplaneta? Do female American cockroaches 

preferentially use sperm from the capsular branch of the 

spermatheca? Is there differential use of the sperm from 

the four spermathecal chambers of German cockroaches? 

If so, is the male virga involved in influencing female 

sperm choice decisions? A creative scientist capable of 

overcoming the technical challenges inherent in these 

kinds of studies could be amply rewarded. 


SEVEN 

Reproduction 

Be fruitful, and multiply, and replenish the Earth. 

—Genesis 1:28 

Perhaps no aspect of cockroach biology has been studied as extensively as the range of 

mechanisms by which they replenish the earth. Understandably so, given that their variation 

in this arena is a rich source of comparative material and that reproduction in many 

species is amenable to laboratory study. Several reviews of cockroach reproduction are 

available, including Roth and Willis (1954b, 1958a), Roth (1970a, 1974a), and Bell and 

Adiyodi (1982b), among others. 

In the majority of cockroaches, reproduction is characterized by the formation of an 

ootheca: eggs are released from the ovaries, move down the oviducts, are oriented into two 

rows by the ovipositor valves, then surrounded by a protective covering. Three general reproductive 

categories are recognized, with two of these broken into subcategories (Table 

7.1) (Roth, 1989a, 1991a, 2003c; Roth and Willis, 1954b, 1958a). In oviparity type A, females 

drop the egg case shortly after formation. In oviparity type B, females carry the 

ootheca externally throughout embryonic gestation, then drop it immediately prior to 

hatch; eggs also may hatch while the ootheca is attached to the mother. Ovoviviparous females 

gestate eggs internally, but the embryos rely primarily on yolk nutrients to fuel and 

support development. In category A ovoviviparous females, the ootheca is first extruded, 

as in oviparous taxa, but it remains attached and is retracted a short time later into a brood 

sac. When the nymphs are ready to hatch, the ootheca is fully extruded and the neonates 

emerge from their embryonic membranes. The eggs are deposited directly from the 

oviducts into the brood sac in ovoviviparous type B species; there is no oothecal case. In viviparous 

forms, oviposition is similar to the ovoviviparous type A cockroaches, but the embryos 

are nourished within the brood sac on a proteinaceous fluid secreted by the mother. 

OVIPARITY 

Oviparous type A cockroach species characteristically produce an ootheca, a double row 

of eggs completely enclosed by a protective outer shell (Stay, 1962; Roth, 1968a). A raised 

116

Table 7.1. Modes of reproduction in cockroaches. After Roth (1989a, 2003c). 

Characters Oviparity A Oviparity B Ovoviviparity A 1 Ovoviviparity B 2 Viviparity 3 

Handling of ootheca Dropped shortly after Carried externally After it is formed, No ootheca; eggs After it is formed, 

formation throughout gestation retracted into the pass directly into retracted into 

brood sac brood sac the brood sac 

Physical properties Hard and dark, Proximal end is In most, variably — Incomplete 

of egg case completely enclosing permeable reduced and membrane 

eggs 

incomplete 

Water handling Sufficient water in Obtains water from Obtains water from Obtains water from Obtains water 

eggs, or additional the female during the female during the female during from the female 

water absorbed from embryogenesis embryogenesis embryogenesis during embryosubstrate 

genesis 

Pre-partition non- No Water-soluble Probably water- Probably water- Proteinaceous 

yolk nutrients from material soluble material soluble material secretion from 

mother? 

walls of brood 

sac 

Taxa All but Blaberidae A few Blattellidae A few Blattellidae, One tribe of Bla- One known speand 

some Blattel- most Blaberidae beridae (Geosca- cies of Blaberilidae 

pheini) dae 

Examples Periplaneta, Blattella, Blaberus, Macropanesthia, Diploptera 

Eurycotis Lophoblatta Nauphoeta Geoscapheus punctata 

1 

”False” ovoviviparity of earlier studies. 

2 

”True” ovoviviparity. 

3 

”False” viviparity. 

crest, the keel, runs along the mid-dorsal line of the egg 

case, and at hatch, the nymphs swallow air, forcing open 

this line of weakness (as in the opening of a handbag). 

The hatchlings generally exit en masse, and the keel snaps 

shut behind them (Fig. 7.1). If some eggs are lost due to 

unviability, parasitism, or disease, the entire brood may 

fail to hatch, because opening the keel typically requires a 

group effort. The ootheca is structurally sophisticated 

(Lawson, 1951; D.E. Mullins and J. Mullins, pers. comm. 

to CAN), and functions in gas exchange, water balance, 

and mechanical protection. 

The oothecae of oviparous type A cockroaches vary in 

their ability to prevent water loss from the eggs (Roth and 

Willis, 1955c). In some species the ootheca and eggs at 

oviposition do not contain sufficient moisture for embryogenesis; 

in these the ootheca must be deposited in a 

humid or moist environment where the eggs absorb water 

(e.g., Ectobius pallidus, Parcoblatta virginica). Alternatively, 

if the ootheca and eggs contain sufficient moisture 

for the needs of the embryos at the time of oviposition, 

the ootheca possesses a protective layer that retards water 

loss (e.g., Blatta orientalis, Periplaneta americana, Supella 

longipalpa). The eggs of Blatta orientalis hatch even if 

oothecae are kept at 0% relative humidity during development. 

When physically abraded, however, the oothecae 

lose 60% or more of their water within 10 days, while controls 

lose only 5% (Roth and Willis, 1955c, 1958a). 

Oothecal Deposition and Concealment 

Fig. 7.1 Unidentified neonate cockroaches freshly hatched 

from an ootheca attached to a leaf, Bukit Timah, Malaysia. Note 

that the keel has snapped shut behind them. Photo courtesy of 

Edward S. Ross. 

The majority of oviparous type A cockroaches select and 

prepare a site for egg case deposition with some care 

(Chapter 9; Roth and Willis, 1960; Roth, 1991a), and the 

stereotyped behavioral sequences involved have been 

used as taxonomic characters (McKittrick, 1964). Therea 

petiveriana simply deposits oothecae randomly in dry 

leaves (Ananthasubramanian and Ananthakrishnan, 1959). 

Other species attach them to the substrate (with saliva or 

genital secretions), and many find or construct a crevice, 

REPRODUCTION 117

direct sunlight. In species that leave oothecae exposed, the 

egg case may be cryptically colored. Shelford (1912b) described 

the ootheca of an unknown species from Ceylon 

(now Sri Lanka) that was attached to the upper surface of 

a leaf. It was white, mottled with brown, and looked “singularly 

like a drop of bird’s excrement.” 

External Egg Retention 

Fig. 7.2 The diurnal Australian cockroach Polyzosteria mitchelli 

digging a hole for hiding her ootheca. It is a beautiful 

species, with a bronze dorsal surface spotted and barred with 

orange or yellow, a pale yellow ventral surface, and sky-blue 

tibiae. The lively colors fade after death. Photo by E. Nielsen, 

courtesy of David Rentz. 

glue the ootheca in a precise position inside it, then conceal 

it with bits of debris, pieces of the substrate, or excrement 

(Fig. 7.2). Ootheca concealment is known in 

blattids (e.g., Blatta orientalis, Eurycotis floridana, 

Methana marginalis, Pelmatosilpha purpurascens, Periplaneta 

americana, P. australasiae, P. brunnea, P. fuliginosa), 

blattellids (Ectobius sylvestris, Parcoblatta pennsylvanica, 

Supella longipalpa, Loboptera decipiens, Ellipsidion 

affine, Ell. australe), and cryptocercids (Cryptocercus 

punctulatus). In the latter, wood and saliva are used to 

pack oothecae into slits carved in the ceilings of their 

wood galleries; the keels of the oothecae are left uncovered 

(Nalepa, 1988a). Concealment behavior may vary 

among closely related cockroach species. Female Ectobius 

pallidus, for example, carefully bury their oothecae after 

deposition; E. lapponicus and E. panzeri seldom do 

(Brown, 1973a). Intraspecific variation in this behavior 

may depend to some extent on the substrate on which the 

insects are found or maintained. Nyctibora noctivaga simply 

drops its ootheca in the laboratory, but in Panama, 

oothecae were found glued to leaves and in crevices of the 

piles supporting a house (McKittrick, 1964). Although 

females whose eggs absorb water from the substrate have 

to be exceptionally discriminating in where they place 

oothecae, they do not always make wise choices. In five 

species of Parcoblatta, it is common to find shrunken 

oothecae, as well as oothecae that have burst and extruded 

material from the keel (Cochran, 1986a). A great 

many unhatched and shriveled oothecae of Parc. pennsylvanica 

were found under the bark of pine logs in an early 

stage successional forest by Strohecker (1937); mortality 

was attributed to the high temperature of logs exposed to 

In cockroaches displaying oviparity type B, the egg cases 

are carried externally for the entire period of embryogenesis 

with the end of the ootheca closely pressed to the 

vestibular tissues of the female’s genital cavity. The proximal 

end of the egg case is permeable, allowing for transport 

of water from the female to the developing eggs 

(Roth and Willis, 1955b, 1955c; Willis et al., 1958). Recently, 

Mullins et al. (2002) injected radiolabeled water 

into female Blattella germanica carrying egg cases. The 

water was detected moving from the female to the proximal 

end of her ootheca, then spreading throughout the 

egg case following a concentration gradient (Fig. 7.3). A 

variety of water-soluble materials were also transferred 

across the female-ootheca divide, including glucose, leucine, 

glycine, and formate. Preliminary experiments of 

these authors indicate that the labeled materials also can 

be detected in nymphs after hatch. Scanning electron microscopy 

and the use of fluorescent stains pinpointed the 

structural basis of flow into the ootheca (Fig. 7.4). Small 

pores completely penetrating the oothecal covering are 

Fig. 7.3 Distribution of radiolabel in oothecae attached to 

Blattella germanica females at four time intervals after injection 

of 3 H 2 

O into the females. See original paper for sample sizes 

and variation. After Mullins et al. (2002), with permission from 

The Journal of Experimental Biology. Image courtesy of Donald 

and June Mullins. 

118 COCKROACHES

that her increased activity level initiates it (D. E. Mullins 

and K. R. Tignor, pers. comm. to CAN). 

Oviparity type B occurs in two subfamilies of Blattellidae. 

In the Blattellinae, at least nine species of Blattella 

and one species of the closely related Chorisia exhibit this 

reproductive mode (Roth, 1985). In the Pseudophyllodromiinae 

two species of Lophoblatta carry their oothecae 

externally throughout gestation. The first of these was 

found by LMR in the Amazon basin in 1967; a female 

Loph. brevis carrying an ootheca was collected on a banana 

plant, and the eggs hatched the following day. A second 

species with external egg retention, Loph. arlei, was 

taken from a bird nest. All other known Lophoblatta deposit 

their oothecae shortly after they are formed (Roth, 

1968b). 

OVOVIVIPARITY 

Fig. 7.4 Scanning electron microscopy images of Blattella germanica 

oothecae, demonstrating the morphological basis of 

their permeability. (A) Proximal end of an ootheca showing the 

“escutcheon-shaped” vaginal imprint (arrow). (B) Magnification 

of the ventro-lateral escutcheon region; arrow indicates 

the pore field area. (C) Magnification of the pore-field area. (D) 

Pores. From Mullins et al. (2002), with permission from The 

Journal of Experimental Biology. Images courtesy of Donald 

and June Mullins. 

found in the wrinkled region surrounding the “escutcheon-shaped” 

vaginal imprint on the proximal end 

(Mullins et al., 2002). 

Because the barrier between mother and developing 

embryos is permeable, females that externally carry egg 

cases throughout gestation have the advantage of parceling 

water and other soluble materials to the embryos on 

an “as needed” basis. They also have some degree of behavioral 

control over the embryonic environment. 

Nymphs of B. germanica are known to settle in microhabitats 

where temperatures are favorable to their development 

(Ross and Mullins, 1995); it is probable that a female 

carrying an egg case acts similarly on behalf of her 

embryos. In most instances, hatch of the egg case is initiated 

while it is still attached to the mother. The activity 

level of the female increases significantly prior to hatch, 

indicating either that she can detect impending hatch, or 

Ovoviviparity occurs in all Blaberidae except the viviparous 

Diploptera punctata, and in four genera of Blattellidae: 

Sliferia, Pseudobalta (Pseudophyllodromiinae) 

(Roth, 1989a, 1996), Stayella, and Pseudoanaplectinia (Blattellinae) 

(Roth, 1984, 1995c). As in oviparous cockroaches, 

type A ovoviviparous species extrude the ootheca as it is 

being formed. When oviposition is complete, however, 

the egg case is retracted back into the body and incubated 

internally in a type of uterus, the brood sac, throughout 

development. The brood sac is an elaboration of the 

membrane found below the laterosternal shelf in oviparous 

cockroaches and is capable of enormous distension 

during gestation (Fig. 6.14). The eggs have sufficient 

yolk, but must absorb water from the female to complete 

development. At hatch, the nymphs are expelled from this 

maternal brood chamber, and quickly shed their embryonic 

cuticle. There is some evidence that pressure exerted 

by the female on the ootheca during extrusion supplies 

the hatching stimulus (Nutting, 1953a). 

Ovoviviparous females are thought to provide only water 

and protection to embryos during gestation, with the 

yolk serving as the main source of energy and nutrients. 

This is supported by data indicating that in ovoviviparous 

Rhyparobia maderae and Nauphoeta cinerea, water content 

increases and dry weight decreases during embryogenesis, 

just as it does in oviparous P. americana (Roth 

and Willis, 1955c; Roth, 1970a). Even if it is not reflected 

as weight gain, however, ovoviviparous cockroaches may 

be supplying more than water to their retained embryos. 

This is suggested by the physiological intimacy of the embryonic 

and maternal tissues, and the evidence that maternal 

transfer of materials occurs in oviparous B. germanica. 

Based on morphological evidence, Snart et al. 

(1984a, 1984b) suggested that Byrsotria fumigata and 

Gromphadorhina portentosa, two Blaberidae commonly 

REPRODUCTION 119

considered ovoviviparous, should in fact be classified as 

viviparous. The surface of the brood sac in these two 

cockroaches is covered with numerous, closely packed 

papillae. Pores in the apical region of each papilla exude 

material thought to result from secretory activity of the 

brood sac, and the brood sac wall has ultrastructural features 

characteristic of insect integumentary glands. These 

authors suggest that the brood sac in these two ovoviviparous 

cockroaches is sufficiently similar to that of the viviparous 

D. punctata to make it likely that the brood sacs 

of all three function in the same manner. Depriving female 

Byr. fumigata and G. portentosa of food and water 

resulted in smaller nymphs, but the relative effects of food 

and water deprivation are unknown. Recent behavioral 

observations of G. portentosa indicate that the brood sac 

indeed may be producing secretions that serve as nutrition 

to young cockroaches; however, the material is expelled 

and ingested by neonates immediately after hatch 

instead of while they are embryos developing inside their 

mother (Chapter 8). Until demonstrated otherwise, then, 

G. portentosa should be considered ovoviviparous, with 

post-hatch parental feeding. 

Four genera of Blaberidae, Macropanesthia, Geoscapheus, 

Neogeoscapheus, and Parapanesthia (Rugg and Rose, 

1984b, 1984c), are classified as ovoviviparous type B and 

deposit their eggs directly into the brood sac, where they 

form a jumbled mass (Fig. 7.5B) rather than the two rows 

Fig. 7.5 Oothecae of two Panesthiinae. (A) Thin, membranous, 

incomplete oothecal case of Panesthia cribrata (ovoviviparity 

A). (B) Massed eggs of Geoscapheus dilatatus, a species 

that lacks an oothecal case (ovoviviparity B). Photos courtesy 

of Harley Rose. 

typical of other cockroaches (Fig. 7.5A). These are the 

only cockroach taxa known to deposit eggs without forming 

an ootheca. Some species in the same subfamily 

(Panesthia australis, Pane. cribrata) exhibit an apparent 

intermediate stage, where some eggs occur in parallel 

rows within an incomplete oothecal membrane, while 

others are applied haphazardly to its outer surface as the 

ootheca is retracted. In Pane. australis, 90% of examined 

oothecae had eggs externally attached to the egg case 

(Rugg and Rose, 1984b, 1984c; D. Rugg, pers. comm. to 

CAN). 

VIVIPARITY 

Diploptera punctata is the only known viviparous species 

of cockroach. Its ootheca contains about a dozen small 

eggs and has an incomplete oothecal membrane (Roth 

and Hahn, 1964). Initially the eggs lack sufficient yolk and 

water to complete development (Roth and Willis, 1955a), 

but embryos ingest water and nutritive material synthesized 

and transported by the walls of the brood sac at a 

rate paralleling embryonic growth (Stay and Coop, 1973, 

1974; Ingram et al., 1977). The brood sac “milk” is composed 

of about 45% protein, 5% free amino acids, 25% 

carbohydrates, and 16–22% lipids. The milk proteins are 

encoded by a multigene family that arose via the modification 

of genes preexisting in ovoviviparous species 

(Williford et al., 2004). Embryos begin oral intake of the 

milk just after closure of their dorsal body wall and continue 

until shortly before partition. The ultimate source 

of nutrition for the embryos is the food intake of the 

mother; females normally double their body weight during 

gestation, and the embryos of starved females die. 

Diploptera nymphs are large and well developed when 

they emerge, requiring fewer molts to adulthood than any 

studied cockroach. Egg fresh weight increases more than 

73 times during gestation (Table 7.2) (Roth and Willis, 

1955a), while the fresh weight of the ovoviviparous 

species N. cinerea doubles. In the latter, the weight increase 

is correlated solely with the absorption of water; 

solids are slowly lost until partition (Roth and Willis, 

1955c). Neonates of D. punctata are at least twice the size 

of those of N. cinerea (see Fig. 3 in Roth and Hahn, 1964), 

yet adults of the latter are considerably larger than fieldcollected 

adults of D. punctata (approximately 27 mm 

and 17 mm in length, respectively—Cochran, 1983a; 

WJB, unpubl. data). Diploptera females have three or four 

post-embryonic instars, compared with the usual seven 

to 13 in a sample of 11 other species of Blattaria (Willis et 

al., 1958). This suggests that D. punctata completes a substantial 

proportion of its juvenile development as an embryo, 

with a corresponding decrease in the duration of 

post-embryonic development. During embryogenesis, 

120 COCKROACHES

Table 7.2. Changes in wet weight, water, and solids of cockroach 

eggs during embryogenesis (Roth and Willis, 1955a). 

closure of the dorsal body wall occurs at 19% of gestation, 

after which the embryos begin feeding on maternal secretions 

(Stay and Coop, 1973). Dorsal closure occurs at 

46% of gestation time in R. maderae (Aiouaz, 1974), at 

50% of gestation in N. cinerea (Imboden et al., 1978), and 

at 56% of gestation in P. americana (Lenoir-Rousseaux 

and Lender, 1970). Gestation of D. punctata embryos 

takes 63 days at 27C (Stay and Coop, 1973); nymphs require 

just 43 to 52 days to become adults (Willis et al., 

1958). 

As might be expected of a group of embryos competing 

for food in a limited space, fewer eggs incubated by 

the mother results in larger nymphs. This was shown experimentally 

by Roth and Hahn (1964), who reduced the 

size of the litter in D. punctata by surgically removing one 

of the ovaries. Neonates in these broods were larger than 

those of control families, presumably because of the 

greater amount of nutritive material made available to 

the fewer developing embryos. In ovoviviparous N. 

cinerea, R. maderae, and Eublaberus posticus, however, the 

size of nymphs remains constant regardless of the number 

of incubated eggs (Roth and Hahn, 1964; Darlington, 

1970). Nymphs within the same ootheca of D. punctata 

also can differ considerably in size depending on their position 

during development; embryos that have poor contact 

with the wall of the brood sac have less ready access 

to the nutritive secretion provided by the mother (Roth 

and Hahn, 1964). Neonate size, in turn, influences the 

number of stadia required to reach adulthood, the developmental 

response of individuals to their social environment, 

final adult size, and male sexual performance 

(Woodhead, 1984; Holbrook and Schal, 2004). 

PARTHENOGENESIS 

Factors by which initial weights 

change, per egg 

Species Wet weight Water Solids 

Blatta orientalis 1.21 1.35 0.96 

Blattella vaga 1.12 1.32 0.81 

Blattella germanica 1.21 1.49 0.74 

Nauphoeta cinerea 2.11 4.62 0.81 

Diploptera punctata 73.47 85.80 49.28 

In a number of cockroach species, females are known to 

switch to an asexual mode of reproduction when isolated 

from males. The resultant offspring are always females, 

that is, these cockroaches display facultative thelytokous 

parthenogenesis. The phenomenon is known in Blatta 

orientalis, B. germanica, Byr. fumigata, E. lapponicus, E. 

pallidus, N. cinerea, P. americana, P. fuliginosa, Polyphaga 

saussurei, and Su. longipalpa (Roth and Willis, 1956; 

Barth, in Roth and Stay, 1962a; Brown, 1973a; Xian, 

1998). Not all females of N. cinerea can reproduce by 

parthenogenesis; only those with a high level of heterozygosity 

are capable, and the ability tends to run in 

families (Corley et al., 2001). Parthenogenesis is rather 

common in P. americana, and can persist through two 

generations in the laboratory (Roth and Willis, 1956). 

Asexual reproduction, however, is clearly a fallback strategy 

that results in significantly reduced fitness in comparison 

to mated females. Nauphoeta cinerea virgins produce 

10-fold fewer offspring than mated females, and 

nymphs are less viable, take longer to develop, have 

shorter adult life spans, and produce fewer offspring of 

their own when mated (Corley and Moore, 1999). Asexually 

produced oothecae, embryos, and hatched nymphs 

are often visibly deformed (Griffiths and Tauber, 1942a; 

Roth and Willis, 1956; Xian, 1998), and in Ectobius, few 

nymphs develop beyond the second instar (Brown, 

1973a). Although the chromosome numbers of asexually 

produced embryos of N. cinerea ranged from 2n 19 to 

40, only those with the karyotype typical of the species 

(2n 36) completed development to the hatching stage 

(Corley et al., 1999). Extreme variation in embryonic development 

within an ootheca can cause failure of the entire 

clutch. If few eggs develop, nymphs may be trapped 

in the oothecal casing, as hatch seems to require a group 

effort even in the thin, membranous oothecae of ovoviviparous 

cockroaches (Roth, 1974b). 

Two cockroach species are known to be exclusively 

parthenogenetic. The best known is the cosmopolitan 

Surinam cockroach, Pycnoscelus surinamensis. This taxon 

is the asexual form of its sibling species Pyc. indicus (Roth, 

1967b), and includes at least 21 diploid clones derived independently 

from sexual females and 11 triploid clones 

produced by backcrosses between clones and Pyc. indicus. 

There are more than 10 clones of Pyc. surinamensis in the 

southeastern United States alone (Roth and Cohen, 1968; 

Parker et al., 1977; Parker, 2002). In laboratory experiments 

females of Pyc. surinamensis tended to resist the 

overtures of male Pyc. indicus, but a few did mate and 

sperm transfer was successful. In these, the oocytes matured 

at the same rate as in virgins. Fertility was reduced, 

however, and all of the resultant offspring were female 

(Roth and Willis, 1961). In the bisexual Pyc. indicus, the 

oocytes of virgins develop slightly more slowly than those 

of mated females, but the proportion of oocytes that mature 

is the same. The oothecae, however, are almost always 

dropped without being retracted into the brood sac (Roth 

and Willis, 1961). Sperm in the spermathecae are re- 

REPRODUCTION 121

quired for normal oothecal retraction in this species (Stay 

and Gelperin, 1966), and if the ootheca is not quickly retracted, 

the enclosed eggs desiccate and die (Roth and 

Willis, 1955c). The evolution of parthenogenesis in Pycnoscelus, 

then, was dependent on overriding this dependence 

on sperm for oothecal retraction. 

The number of eggs produced and matured by the obligately 

parthenogenetic Pyc. surinamensis is significantly 

less than that produced by sexual reproduction in its sister 

species (Roth, 1974b). Nonetheless, Pyc. surinamensis 

readily becomes established in a new location via a single 

nymph or adult, and has a widespread distribution (Roth, 

1998b). It is found in tropical and subtropical habitats 

throughout the world, and in protected habitats, particularly 

greenhouses, in temperate climates (Roth, 1974b, 

1998b). Its sexual sibling species Pyc. indicus is native to 

Indo-Malaysia and adjacent parts of Southeast Asia, and 

has colonized islands in the Pacific (Hawaii) and Indian 

(Mauritius) oceans. Both species may be found around 

human habitations, and both burrow in soil and are poor 

flyers. The widespread distribution of the asexual form is 

undoubtedly due to human transport, but the distribution 

pattern is also typical of geographic parthenogenesis 

(Niklasson and Parker, 1996), a condition in which a thelytokous 

race has a more extensive distribution than its 

sexual ancestor (Parker, 2002). Pycnoscelus has been used 

as a model to explore a variety of hypotheses on the subject 

(Gade and Parker, 1997; Niklasson and Parker, 1994; 

Parker, 2002; Parker and Niklasson, 1995). 

Until recently, Pyc. surinamensis was the only case of 

obligatory parthenogenesis known in cockroaches. In 

2003, a second case was reported in the Mediterranean 

blattellid species Phyllodromica subaptera by Knebelsberger 

and Bohn. The distribution of the sexual and asexual 

forms was studied by analyzing spermathecal contents 

and the sex of offspring. As in Pycnoscelus, the 

distribution of Phy. subaptera exhibits a pattern of geographic 

parthenogenesis: the asexual form is spread over 

most Mediterranean countries, while the bisexual forms 

are restricted to the Iberian peninsula. The parthenogenetic 

and sexual strains of Phy. subaptera cannot be 

distinguished by external morphology, suggesting that 

parthenogenesis is a relatively recent acquisition in the 

taxon. 

FACTORS INFLUENCING REPRODUCTION 

A variety of interacting factors are known to have an impact 

on the reproduction of female cockroaches, including 

food availability, body size, mating status, social contacts, 

and age (reviewed by Engelmann, 1970; Roth, 

1970b). The presence of conspecifics accelerates reproduction 

in B. germanica, not only by influencing food intake 

but also via a more direct effect on juvenile hormone 

synthesis (Holbrook et al., 2000a). In N. cinerea maternal 

age is negatively correlated with fertility and lifetime fecundity. 

Old females take significantly longer than young 

ones to produce a first clutch. They also include fewer 

eggs per ootheca, and those eggs are slower to develop. 

Maternal age does not affect hatch rate, viability, nymphal 

development, or the reproductive potential of these 

nymphs when they became adults. While age does affect 

maternal fitness, then, it has no effect on the fitness of the 

offspring older females produce (Moore and Moore, 

2001; Moore and Harris, 2003). 

Species are differentially dependent on stored reserves 

for their first oviposition, varying from complete dependence 

(e.g., R. maderae—Roth, 1964b), to complete independence 

(e.g., Pycnoscelus—Roth and Stay, 1962a) 

(Table 7.3). Reproduction in relatively small blattellids 

can be closely tied to food availability. Females of B. germanica 

invest 34% of their pre-oviposition dry weight 

and 26% of their nitrogen into their first ootheca 

(Mullins et al., 1992). Female Parc. fulvescens typically 

store sufficient reserves to produce just one egg case, constituting 

15–20% of her body weight (Cochran, 1986a; 

Lembke and Cochran, 1990). In larger species like Periplaneta, 

food intake is not necessary to mature the first 

batch of eggs, and females can produce up to five oothecae 

without feeding between successive ovipositions 

(Kunkel, 1966). Oothecae are just 7% of the weight of the 

unstarved female (Weaver and Pratt, 1981). Mating and 

feeding seem to have a synergistic effect in N. cinerea and 

R. maderae, since both stimuli are usually required for the 

Table 7.3. Effect of starvation during the first preoviposition 

period in virgin and mated female cockroaches. See Roth 

(1970b) for citations of original work. 

Oocyte development 1 

Fed 

Starved 

Species Virgins Mated Virgins Mated 

Blattella germanica 

Blattella vaga 

Blaberus craniifer 

Byrsotria fumigata 

Eublaberus posticus 

Nauphoeta cinerea 

Rhyparobia maderae 

Pycnoscelus indicus 

Pycnoscelus surinamensis 

Diploptera punctata 

1 

() develop and mature rapidly; () develop and mature; () may 

or may not develop; () do not develop. 

122 COCKROACHES

maximum rate of yolk deposition (Roth, 1964a, 1964b). 

Mating is necessary for initiation of yolk deposition in D. 

punctata (Engelmann, 1960; Roth and Stay, 1961), but has 

no effect on yolk deposition in Byr. fumigata, Pyc. indicus, 

or B. germanica (Roth and Stay, 1962a). Stimuli from 

feeding, drinking, mating, and social contact are required 

for the highest rates of yolk deposition in P. americana. A 

graded series of “sexually suppressed”females can be produced 

by withholding one or more of these stimuli 

(Weaver, 1984; Pipa, 1985). 

EGG NUMBER AND SIZE 

Comparisons of reproductive investment within a taxon 

require the resolution of differences attributable to body 

size. Although little information on the subject has been 

compiled for cockroaches, we do know that the body 

length of adults in the smallest species can be 3% the 

length of the largest (Chapter 1), making them good 

candidates for investigations on the allometry of reproduction. 

At the species level there appears to be little 

relationship between the size of the mother and the 

packaging of the reproductive product. In the oviparous 

cockroaches, 18 mm long Cartoblatta pulchra females 

place about 95 eggs into an ootheca, more than any other 

species of Blattidae (Roth, 2003b). Ovoviviparous cockroaches 

average about 30 eggs per ootheca, but the relatively 

small Panchlora produces broods larger than a 

Blaberus 10 times its size and mass. Panchlora nivea is 2.5 

cm long and internally incubates 60 or more eggs per 

clutch. The egg case is distorted into a semicircular or J- 

shape so that it may be internally accommodated (Roth 

and Willis, 1958b). The record, however, probably belongs 

to African Gyna henrardi, which somehow puts up 

to 243 eggs into a z-shaped ootheca that she stuffs into her 

brood sac (Grandcolas and Deleporte, 1998). Hatch must 

resemble the endless supply of clowns exiting a miniature 

car at the circus. 

We know little regarding relative egg sizes among cockroaches. 

Two species with large post-ovulation investment 

are known to lay small eggs. In C. punctulatus eggs 

are only 44% of expected size for an oviparous cockroach 

of its dimensions (Nalepa, 1987). Most resources are 

channeled into an extensive period of post-hatch parental 

care and into the maintenance of the long-lived adults 

(Nalepa and Mullins, 1992). At hatch neonates in this 

species are tiny, blind, dependent, and fragile (Nalepa and 

Bell, 1997). Viviparous D. punctata also produces small 

eggs, with yolk insufficient to complete development 

(Roth, 1967d). As with all viviparous animals, supplying 

embryos with gestational nutrients places less reliance on 

producing large yolky oocytes. Neonates emerge at the 

precocial extreme of the developmental spectrum, with 

the largest relative size and shortest postembryonic development 

known among cockroaches. 

EVOLUTION OF REPRODUCTIVE MODE 

Of the two major divisions of the cockroaches, the superfamilies 

Blattoidea and Blaberoidea (McKittrick, 1964), 

most evolutionary drama with regard to reproductive 

mode is in the latter. It includes the Blattellidae, in which 

some species retain the egg case externally for the entire 

period of gestation, and where ovoviviparity arose independently 

in two different subfamilies. It also includes the 

Blaberidae, all of which incubate egg cases internally, suggesting 

that they have radiated since an ancestor acquired 

the trait. The sole viviparous genus, as well as the group 

that lost the oothecal covering, are in the Blaberidae. Of 

course, critical analysis of the pattern of reproductive 

evolution is dependent on the availability of robust phylogenies 

for the groups under study, but, as with most aspects 

of cockroach systematics, the relationships among 

several subgroups of the Blaberoidea are unsettled. In all 

phylogenetic hypotheses proposed so far, however, Blaberidae 

is most closely related to Blattellidae (Roth, 

2003c), and some studies (Klass, 1997, 2001) suggest that 

blaberids are a subgroup of the Blattellidae. 

The evolution of reproductive mode in cockroaches 

can be described with some confidence as a unidirectional 

trend from oviparity to viviparity, without character 

reversals. Reproduction is an extraordinarily complex 

process, with morphology, physiology, and behavior integrated 

and coordinated by neural and endocrine mechanisms. 

Transitions therefore tend to be irreversible due to 

genetic or physiological architecture, or because strong 

selection on offspring prevents them (Tinkle and Gibbons, 

1977; Crespi and Semeniuk, 2004). An initial step in 

the evolution of ovoviviparity in cockroaches was likely 

to be facultative transport of the egg case, as in the 

oviparous type A species that retain oothecae until a suitable 

microhabitat is found. Ectobius pallidus, for example, 

typically deposits its egg case in one or two days, but has 

been reported to carry it 16 days or longer (Roth and 

Willis, 1958a). Therea petiveriana deposits the ootheca 

within a day of extrusion, but may retain it for as long as 

90 hr if a suitably moist substrate is not available (Livingstone 

and Ramani, 1978). From this flexible starting 

point, the trend toward ovoviviparity would be exemplified 

by cockroaches that retain the egg case for the entire 

period of embryogenesis, but provide no materials 

additional to those originally in the egg case. Currently, 

there are no records of extant cockroaches that exhibit 

this pattern; the only oviparous type B species that has 

been studied, B. germanica, provides water and soluble 

materials to embryos. Obligate egg retention evolves 

REPRODUCTION 123

when maternal tissues became responsive to the attached 

egg case; this recognition then induces further modifications 

of maternal function (Guillette, 1989). 

Oothecal Rotation 

The position of the ootheca while it is carried prior to deposition 

is taxonomically significant and important in 

understanding the evolution of reproductive mode in 

cockroaches (Roth, 1967a).All of the Blattoidea and some 

of the Blaberoidea carry the ootheca with the keel dorsally 

oriented. However, in some Blattellidae and in all of the 

Blaberidae, the female rotates the ootheca 90 degrees so 

that the keel faces laterad at the time it is either deposited 

on a substrate, carried externally for the entire period of 

embryogenesis, or retracted into the brood sac. Within 

the Blattellidae, rotation of the ootheca has been used as 

a taxonomic character to separate the non-rotators (Anaplectinae 

and Pseudophyllodromiinae) from the rotators 

(Blattellinae, Ectobiinae, and Nyctoborinae) (McKittrick, 

1964). Most studies (McKittrick 1964; Roth, 1967a; Bohn, 

1987; Klass, 2001) indicate that ootheca rotation evolved 

just once, and the recent phylogenetic tree of Klass and 

Meier (2006) (see Fig. P.1 in Preface) supports this view. 

One must be careful in determining oothecal rotation in 

museum specimens, as females may have been preserved 

while in the process of oothecal formation, prior to rotation. 

LMR found females with rotated oothecae from 

groups that do not normally exhibit this character; a museum 

worker had glued the oothecae to the females in an 

“incorrect” orientation. Some Polyphagidae exhibit a 

“primitive” or “false” type of rotation in which the 

ootheca is rotated and held by a “handle” or flange at the 

female’s posterior end (Roth, 1967a). This type of rotation 

may have evolved as a way to prevent oothecae from 

being pulled off females as they move through sand (Fig. 

2.6). The oothecae itself does not contact the female’s 

vestibular tissues and ovoviviparity did not evolve in this 

group. 

Transition to Live Bearing 

Oothecal rotation is a key character when comparing the 

cockroach lineages that evolved ovoviviparity. Only one 

of the two subfamilies of Blattellidae exhibiting this reproductive 

mode rotates its egg case, but rotation occurs 

in all Blaberidae. Within the Blattellinae, the oviparous 

type B species, as exemplified by B. germanica, rotate the 

ootheca 90 degrees once it is formed and females carry it 

that way throughout gestation (Fig. 7.6). The ootheca is 

thus reoriented from its initial vertical position to one in 

which the long axes of the oocytes lay in the plane of the 

female’s width. When first formed the egg cases are much 

Fig. 7.6 Blattella germanica female carrying a fully formed 

ootheca (scale mm). Photo courtesy of Donald Mullins. 

taller than they are wide, like a package of frankfurters 

standing on end. Rotation likely evolved to prevent dislodgment 

of these egg cases as the morphologically flattened 

females scurried through crevices (Roth, 1968a, 

1989a). Females of B. germanica that carry a rotated 

ootheca are able to crawl into spaces narrower than females 

carrying them in the vertical position (Wille, 1920). 

A gravid female one day before oviposition needs a space 

of 4.5 mm. A female with the ootheca carried in the vertical 

position requires 3.3 mm, and after the egg case is rotated 

the female can move into a space 2.9 mm high. Ovoviviparous 

cockroaches in the same subfamily as Blattella 

(e.g., Stayella) carry within their brood sac a rotated 

ootheca virtually identical to the externally carried, rotated 

egg case of B. germanica (Roth, 1984). 

In the second blattellid subfamily with oviparous type 

B reproduction (Pseudophyllodromiinae), two species of 

Lophoblatta maintain the original vertical position of the 

ootheca while carrying it externally throughout gestation. 

These oothecae, however, are distinctly wider than 

high (Roth, 1968b). Ovoviviparous females in this subfamily 

(e.g., Sliferia) have similarly squat oothecae, and 

retract them while they are vertically oriented, without 

rotation. The two blattellid subfamilies, then, employ different 

but equivalent mechanisms for achieving the same 

end. An ootheca of dimensions appropriate for a crevice- 

124 COCKROACHES

Fig. 7.7 Diagram of presumed sequence of stages in the evolution of ovoviviparity from oviparity in 

two subfamilies of Blattellidae. Note the difference in the orientation of the ootheca between the two 

subfamilies. Current evidence suggests that the oothecal rotation exhibited by the Blattellinae and by 

the ovoviviparous Blaberidae originated in a common ancestor. 

dwelling insect to carry or internalize must be either 

squashed dorsoventrally or rotated so that it is as flat as 

the female (Fig. 7.7). Intermediate stages in parity mode 

are conspicuous in the Pseudophyllodromiinae. Sliferia 

is considered ovoviviparous; nonetheless the egg case is 

partially exposed while it is carried. Initially it was 

thought that these females were collected while still forming 

the ootheca. Now this condition is considered the 

norm, and points up the continuum of reproductive 

modes in this subfamily (Roth, 2003b). 

All species in the ovoviviparous family Blaberidae 

carry a rotated egg case in their brood sac and are thought 

to have evolved from a Blattella-like ancestor (Roth and 

Willis, 1955c; Roth, 1967a; Mullins et al., 2002). Except for 

retraction of the egg case into the body, B. germanica exhibits 

all characteristics of an ovoviviparous cockroach 

(Roth and Willis, 1958a; Roth, 1970a). The oothecal case 

is thinner and less darkly colored than in other oviparous 

cockroaches, there is flow of water and other materials between 

mother and unhatched offspring, and oogenesis is 

suspended while females are carrying egg cases. The evolution 

of ovoviviparity would require only a minor transition 

from that starting point. Ovoviviparity evolved independently 

two or three times in cockroaches, but only 

in the blattellid/blaberid lineage (Roth, 1970a, 1989a): 

once in the Pseudophyllodromiinae, and once or twice in 

the clade that includes Blattellinae and Blaberidae. Viviparity 

evolved once, in D. punctata of the monogeneric 

subfamily Diplopterinae. Some authors also include Calolampra 

or Phoetalia in this subfamily (Roth, 2003c), so 

these genera may be logical targets for comparative study. 

Worldwide, Blattellidae is the largest cockroach family 

with about 1740 described species; there are approximately 

1020 species of Blaberidae. The oviposition behavior 

is known in relatively few genera and species of 

these two families (Roth, 1982a). 

Reduction and Loss of the Egg Case 

In most oviparous type A cockroaches, the ootheca is a 

hard, dark, stiff structure completely covering the eggs. 

The dorsal keel is structurally complex, and the outer covering 

contains calcium oxalate crystals. These crystals 

comprise 8–15% of the dry weight of the ootheca in P. 

REPRODUCTION 125

americana, and are thought to have a structural and protective 

function (Stay et al., 1960; Rajulu and Renganathan, 

1966), just as they do in plants that possess 

them (Hudgins et al., 2003). The oothecal casing is thinner 

and less rigid in species that externally carry the egg 

case (oviparous type B); calcium oxalate crystals are 

sparse in both B. germanica and Loph. brevis (Roth, 

1968b). Ovoviviparous type A cockroaches typically produce 

a thin, soft, lightly colored ootheca that lacks a keel 

and which in some species only partially covers the eggs, 

particularly in later stages of gestation (Roth, 1968a) (Fig 

7.5A); calcium oxalate is absent. This type of egg case is 

produced by Blaberidae and also Sliferia, one of few Blattellidae 

that retract their ootheca into a brood sac (Stay et 

al., 1960; Roth, 1968a). The nature of the ootheca, then, 

changes in parallel with stages of internalization of the 

egg case. It goes from having a rigid outer casing in those 

species that abandon the egg case, to a flexible, soft membrane 

in those that have internalized it. It has intermediate 

properties in those cockroaches that carry the ootheca 

externally during gestation, and has been completely lost 

in one derived lineage (Geoscapheini: ovoviviparous type 

B) (Roth and Willis, 1958a; Roth, 1968a, 1970a). Females 

exhibit a parallel regression of the morphological structures 

associated with oothecal production (reviewed by 

Nalepa and Lenz, 2000). 

Oviparous cockroaches in protected environments, 

like social insect nests, also may exhibit reduction or loss 

of the egg case. The ootheca of Attaphila fungicola, for example, 

lacks a keel (Roth, 1971a), and several species of 

Nocticolidae have thin, transparent oothecal cases. Nocticola 

termitophila apparently lays its eggs singly, without 

any external covering (Roth, 1988). Termites, the “social 

cockroaches” (Chapter 9), exhibit a parallel loss of protective 

egg cases. The basal termite Mastotermes darwiniensis 

packages its eggs within a thin, flexible outer 

covering that lacks keel. The site and mode of production, 

associated morphological structures in the female, parallel 

arrangement of eggs, and discrete, tanned outer covering 

together indicate that the ootheca of Mastotermes is 

homologous with those of cockroaches (Nalepa and 

Lenz, 2000). All other termites lay their eggs singly, without 

a covering. Both the heart of a social insect colony and 

the brood sacs of live bearing cockroaches are moist, protected 

sites for incubating eggs, allowing for the reduction 

and eventual elimination of defensive structures in evolutionary 

time. The oothecal case is 86–95% protein 

(Table 4.5), so “it is no wild supposition that in the course 

of time the chitinous ootheca, being in these species a 

work of supererogation, will disappear” (Shelford, 1912b). 

Perhaps the main reason that the ootheca has not been 

completely eliminated in most ovoviviparous cockroaches 

is because it determines the orderly arrangement of eggs 

and therefore assures contact and exchange of water and 

other materials between each egg and the wall of the 

brood sac (Rugg and Rose, 1984b). A study of the Geoscapheini 

whose eggs are incubated in a disordered mass 

in the brood sac (Rugg and Rose, 1984c) (Fig. 7.5B) is the 

logical focal group for testing this hypothesis. 

Selective Pressures 

Most hypotheses offered to explain why live bearing has 

evolved in animals invoke agents affecting offspring viability 

as the selective pressure for an evolutionary shift in 

reproductive mode. Costs that accrue to mothers then either 

facilitate or constrain the transition. These may include 

reduced maternal mobility, with consequences for 

foraging efficiency and predator evasion, reduced fecundity, 

and the increased metabolic demands of carrying 

offspring throughout their development (Shine, 1985; 

Goodwin et al., 2002, among others). It is difficult, however, 

to use present-day characteristics of ovoviviparous 

or viviparous organisms as evidence for hypotheses on 

the evolution of these traits, as current habitats may be 

different from the habitats in which the reproductive 

modes first evolved (Shine, 1989). It is also important to 

note that each strategy has its benefits and liabilities in a 

given environment. Oviparity is not inherently inferior to 

ovoviviparity or viviparity just because it is the ancestral 

state. The problem of water balance in cockroaches, for 

example, is handled by each reproductive mode in different 

ways, each of which may be optimal in different habitats. 

Egg desiccation can be minimized if: (1) the ootheca 

is deposited in a moist environment, (2) the ootheca has 

a waterproofing layer, or (3) the female dynamically 

maintains water balance while the egg case is externally 

attached or housed in a brood sac (Roth, 1967d). 

Increased Offspring Viability 

McKittrick (1964) was of the opinion that the burial and 

concealment of oothecae by oviparous females is a response 

to pressure from parasitoids and cannibals. Although 

few studies directly address this question, some 

evidence suggests that concealing oothecae may attract 

rather than deter hymenopterous parasitoids. The mucopolysaccharides 

in the saliva used to attach egg cases to 

the substrate may act as kairomones, making oothecae 

more vulnerable to attack. Parasitic wasps may even expose 

buried oothecae by digging them out from their 

protective cover (Narasimham, 1984; Vinson and Piper, 

1986; Benson and Huber, 1989). On the other hand, 

oothecae of P. fuliginosa that were glued to a substrate had 

a higher eclosion rate than those that were not glued, suggesting 

that salivary secretions may enhance egg viability 

in some unknown way (Gordon et al., 1994). Oothecae of 

126 COCKROACHES

Fig 7.8 Parasitism of cockroach eggs. (A) Anastatus floridanus 

ovipositing into an ootheca carried by Eurycotis floridana. (B) 

Detail of oviposition by the parasitoid. Photos by L.M. Roth 

and E.R. Willis. 

oviparous cockroaches are also prone to parasitism prior 

to deposition, while females are forming and carrying 

them. The window of vulnerability can be a wide one. Females 

of Nyc. acaciana, for example, can take 72 hr to 

form an ootheca (Deans and Roth, 2003). The parasitoid 

Anastatus floridanus (Eupelmidae) oviposits in egg cases 

attached to female Eur. floridana (Fig. 7.8) (Roth and 

Willis, 1954a). The cockroach can detect the presence of 

the wasp on the surface of the ootheca and tries to dislodge 

it with her hind legs (LMR, pers. obs.). Blattella spp. 

that carry egg cases externally until hatch are also vulnerable 

to egg parasitoids, and continue to carry the parasitized 

ootheca (Roth, 1985). External retention of egg 

cases, then, may be little better than concealment in conferring 

protection from parasitism. 

The value of egg case burial lies primarily in protecting 

them from predation and cannibalism; concealment is almost 

100% effective in saving oothecae from being devoured 

by other cockroaches (Rau, 1940). McKittrick et 

al. (1961) found that in Eur. floridana, burial of oothecae 

prevented cannibalism by conspecifics and predation by 

ants, carabids, rodents, and other predators. Conversely, 

exposed egg cases and those still attached to a female are 

subject to biting and cannibalism (Roth and Willis, 

1954b; Willis et al., 1958; Gorton, 1979). These improprieties 

are countered with aggression on the part of the 

mother. Female P. brunnea, P. americana, and Paratemnopteryx 

couloniana drive other females away from exposed 

oothecae (Haber, 1920; Edmunds, 1957; Gorton, 

1979). Two behavioral classes of female can be distinguished 

in B. germanica; females carrying oothecae are 

more aggressive than females that had not yet formed 

them (Breed et al., 1975). Aggressive behavior is favored 

despite its attendant risks, given that one nip taken from 

an ootheca can result in the death of the entire clutch 

from desiccation (Roth and Willis, 1955b). 

Ovoviviparity is viewed as a solution to this constant 

battle against predators and parasites, and is thought to 

have appeared in the Mesozoic as an evolutionary response 

to cockroach enemies that first appeared during 

that time (Vishniakova, 1968). Parasitoids have not been 

detected in the oothecae of ovoviviparous blaberids 

(LMR, pers. obs.). The eggs are exposed to the environment 

for only the brief period of time between formation 

of the ootheca and its subsequent retraction into the 

body, allowing only a narrow time frame for parasitoid 

oviposition. Once in this enemy free space, the eggs are 

subject only to “the vicissitudes that beset the mother” 

(Roth and Willis, 1954b). Nonetheless, nymphs of ovoviviparous 

cockroaches are at risk from cannibalism at the 

time of hatch. Attempts by conspecifics to eat the hatchlings 

as the female ejects the ootheca have been noted and 

may include pulling the still attached egg case away from 

the mother (Willis et al., 1958). We note, however, that 

laboratory observations of cannibalism in cockroaches of 

any reproductive mode may be of little consequence in 

natural populations, with the exception of highly gregarious 

species like cave dwellers. Females of at least one 

species of the latter are known to be choosy about where 

they expel their neonates. Darlington (1970) reported 

that pregnant females of Eub. posticus preferred one 

chamber of the Tamana cave for giving birth, and migrated 

into that chamber from other parts of the cave. 

Defense against pathogens as agents of egg mortality is 

unstudied, despite the disease-conducive environments 

typical of cockroaches. 

Parental Costs 

Indirect reproductive costs of oviparity in cockroaches 

include the time, energy, and predation risks involved in 

concealing the ootheca in the environment and the metabolic 

expense of producing a protective oothecal case. 

The case consists primarily of quinone-tanned protein 

(Brunet and Kent, 1955) (Table 4.5), much of which can 

be recovered after hatch if the parent or neonates eat the 

embryonic membranes, unviable eggs, and the oothecal 

case after hatch (Roth and Willis, 1954b; Willis et al., 

1958). In several species of cockroaches, oothecal predation 

by adults and the ingestion of oothecal cases after 

REPRODUCTION 127

hatching by nymphs increases when other protein sources 

are lacking (WJB, unpubl. obs.). 

Live bearing permits females to dispense with producing 

a thick, protective oothecal case, and allows them to 

channel the protein that would have been required for its 

manufacture into present or future offspring or into their 

own maintenance. Nonetheless, the burden of “wearing” 

the next generation may be metabolically expensive and 

impair mobility, with consequences for predator evasion 

and foraging efficiency. In B. germanica, however, Lee 

(1994) found no correlation between the physical load on 

the female and oxygen consumption, and in N. cinerea the 

mass-specific metabolic heat flux of pregnant females at 

rest was actually reduced in relation to non-pregnant females. 

This suggests that the energetic demands of gestation 

in these species do not translate into increased metabolic 

rates (Schultze-Motel and Greven, 1998). Still, most 

female cockroaches feed little, if at all, during gestation, 

even when offered food ad libitum in the laboratory (e.g., 

Blattella—Cochran, 1983b; Hamilton and Schal, 1988; 

Rhyparobia—Engelmann and Rau, 1965; Trichoblatta— 

Reuben, 1988). The most commonly offered explanation 

for fasting at this time is that the cumbersome bodies of 

pregnant females may increase their vulnerability to predation. 

This seems reasonable, given that, first, the mass 

of the reproductive product is 30% or more of female 

body weight in both B. germanica (Mullins et al., 1992; 

Lee, 1994) and N. cinerea (Schultze-Motel and Greven, 

1998), and second, pregnant N. cinerea are demonstrably 

slower than virgin females of the same age (Meller and 

Greven, 1996a). Agility also may be affected. Ross (1929), 

however, opined that pregnant B. germanica“do not show 

any signs of being impeded by their burden” despite the 

clumsy ootheca dragging from their nether regions. Loss 

of agility may not be an issue in cockroaches that rely on 

crypsis or thanatosis to escape predators, but the larger 

body of gravid females requires a larger crevice in species 

that seek protective shelter (Koehler et al., 1994; Wille, 

1920). It is unknown whether the physical burden of an 

egg clutch hinders flying in those species that depend on 

it for evasion. Blattella karnyi females can take to the air 

while carrying an impressive ootheca of up to 40 eggs 

(Roth, 1985). 

In viviparous D. punctata, gravid females normally 

double their body weight during gestation but nonetheless 

forage; the nutrient secretion of the brood sac is derived 

from the maternal diet rather than stored nutrients, 

particularly in early pregnancy (Stay and Coop, 1974; 

WJB, unpubl. data). This species has hard, dome-shaped 

tegmina (common name “beetle cockroach”) and impressive 

defensive secretions (Eisner, 1958; Roth and Stay, 

1958) that may permit some bravery when under attack 

by ants (Fig. 1.11A). Vertebrate predators, however, are 

threats, and lizards, toads, and birds have been observed 

eating them in the field (Roth and Stay, 1958; WJB, pers. 

obs.). It is possible that D. punctata females rely on readily 

accessible, predictable sources of high-quality food for 

supporting the explosive growth of their embryos. Their 

diet, however, appears little different from that of many 

other cockroaches. 

Reduced Fecundity 

One of the most significant costs exacted by carrying egg 

cases lies in terms of fecundity. Oviparous type A cockroaches 

have relatively high reproductive rates because 

the interval between successive oothecae is short, usually 

much shorter than the period of incubation. Females typically 

produce a second egg case long before the first laid 

hatches. Oviparous species with external egg retention as 

well as ovoviviparous females produce relatively few 

oothecae because oocytes do not mature in the ovaries 

while an ootheca is being carried. Viviparity is particularly 

expensive, in that female D. punctata have fewer eggs 

per oothecae, produce fewer oothecae per lifetime, and 

have a longer period of gestation than any other blaberid 

(Roth and Stay, 1961; Roth, 1967d). Consequently, the 

number of egg cases per lifetime decreases and the oviposition 

interval increases in the order oviparous, ovoviviparous, 

viviparous (Fig. 7.9) (Willis et al., 1958; Roth and 

Stay, 1959, 1962a; Breed, 1983). 

Fecundity also appears reduced in cockroach species 

that exhibit parental care, particularly if the care involves 

feeding young dependents on bodily fluids. Such pabulum 

may be demanding in terms of the structures involved 

in its manufacture, the nutrients incorporated into 

the secretions, and the energy required to produce them. 

Fig. 7.9 Frequency of oviposition by individuals of different 

species of cockroach. Each dot represents the formation of an 

ootheca; the length of the line is the adult lifespan of the female. 

Symploce pallens ( hospes) and Supella longipalpa (Blattellidae) 

are oviparous and drop the ootheca shortly after it is 

formed. Blattella germanica and B. vaga (Blattellidae) carry 

their ootheca externally until the eggs hatch. The blaberids 

Pycnoscelus surinamensis (parthenogenetic) and Nauphoeta 

cinerea are ovoviviparous, and Diploptera punctata is viviparous. 

After Roth (1970a). 

128 COCKROACHES

Fig 7.10 Post-oviposition provisioning in cockroaches. Oviposition refers to the release of eggs from 

the ovaries, while extrusion is the permanent expulsion of eggs from the body. Deposition is the disassociation 

of the egg case from the body. Independence is the ability of neonates to live apart from 

the parent(s). Modified from Nalepa and Bell (1997), with the permission of Cambridge University 

Press. 

Perisphaerus sp. and Thorax porcellana both exhibit a reduction 

in the number of offspring per clutch as compared 

to other ovoviviparous species (Roth, 1981b). 

PARENTAL INVESTMENT 

In the majority of oviparous type A cockroaches females 

make their principal direct investment prior to fertilization, 

by supplying eggs with yolk nutrients. They then envelope 

the eggs in a protective covering and deposit them 

in a safe place for incubation. With the exception of Cryptocercus, 

there is no additional parental involvement. In 

species with external retention, like Blattella, embryos are 

dependent on yolk to fuel development but are also progressively 

supplied with water and some non-yolk nutrients 

during gestation (Fig. 7.10). This is likewise true of 

ovoviviparous cockroaches, but in several species neonates 

continue their dependence on maternally supplied 

nutrients for a period of time after hatch. These take the 

form of digestive fluids and glandular secretions; at least 

six types are known (Chapter 8). Cockroaches tend to 

have a very glandular integument, allowing for the repeated 

evolution of nutritive secretions from cuticular 

surfaces. Williford et al. (2004) recently demonstrated 

that proteins in the milk secreted by the brood sac of 

Diploptera are coded by genes from the same family 

(lipocalin) as those that code for a protein in the tergal 

gland secretion of R. maderae (Korchi et al., 1999). 

REPRODUCTION 129

One consequence of this variation in investment 

strategies is that it is not always easy to place cockroaches 

into distinct reproductive categories. There is a continuum 

between species that externally retain their egg cases 

and those that internalize them, obvious in Figs. 7.7 and 

7.10. The location of the egg case during gestation differs 

in the Lophoblatta-Sliferia-Pseudobalta series, but the investment 

strategy is basically the same. Another example 

is a comparison between the viviparous Diploptera and 

the ovoviviparous Gromphadorhina. Both species apparently 

provision offspring on secretions that originate 

from the brood sac walls. Diploptera does so progressively, 

during gestation. Gromphadorhina and possibly other 

Blaberidae (Byrsotria, Blaberus, Rhyparobia) (Perry and 

Nalepa, 2003) expel it en masse for consumption by 

nymphs immediately after partition. 

Termination of Investment 

If a female cockroach has initiated a reproductive episode 

that is threatened for lack of food or other reasons, she has 

several options for converting reproductive investment 

back into somatic tissue, thereby maintaining and redirecting 

her resources (Elgar and Crespi, 1992). Termination 

of investment can occur at several points in the reproductive 

cycle. Prior to ovulation, starvation increases 

oocyte resorption in cockroaches (reviewed by Bell and 

Bohm, 1975). In P. americana, most starved females produce 

one, sometimes two, oothecae in addition to the one 

being produced when starvation is initiated (Bell, 1971). 

Large yolk-filled oocytes are retained in the ovaries of 

those females that do not deposit a second ootheca, and 

beginning on about the 10th day of starvation these 

oocytes are resorbed and the vitellogenins stored. When 

feeding resumes, these stored yolk proteins are rapidly 

incorporated into developing oocytes. In Xestoblatta 

hamata, both resorption of proximal oocytes and an extension 

of the interval between oothecae are common in 

the field and are the result of unsuccessful foraging (Schal 

and Bell, 1982; C. Schal, pers. comm. to WJB). 

After ovulation, females have other mechanisms for 

terminating reproductive investment. Abortion can occur 

in laboratory cultures if gestating females are disturbed 

in Pyc. surinamensis, Panchlora irrorata, and 

Blaberus craniifer (Nutting, 1953b; Willis et al., 1958; 

Willis, 1966). It is unknown if and under what circumstances 

ovoviviparous and viviparous cockroaches jettison 

egg cases under natural circumstances; the possibility 

exists that they may relieve themselves of their 

oothecal burden if suddenly pursued by a predator in 

their natural habitat. This tactic may be more likely in 

those cockroaches that that use speed/agility to escape 

predators rather than crypsis or defensive sprays. 

Post-partition, cannibalism can be a means of recovering 

and recycling a threatened reproductive investment. 

If disturbed when nymphs are freshly hatched, adults of 

C. punctulatus may cannibalize their entire brood (CAN, 

unpubl. obs.). Other cockroach species are known to eat 

their young (Roth and Willis, 1954b), and starved females 

are often more likely to do so (Roth and Willis, 1960; 

Rollo, 1984b; WJB, unpubl. obs.). 

130 COCKROACHES

EIGHT 

Social Behavior 

The only useful outcome of my attempt to classify types of parental care into 

mutually exclusive sets was that it made clear that from many points of view by 

far the largest group of insects that exhibit parental care (is) the cockroaches. 

—H.E. Hinton, Biology of Insect Eggs 

It is difficult to conceive of any group of animals that are as universally and diversely social 

as cockroaches. Given the range of habitats they have mastered and their versatility 

in reproductive mode and feeding habits, it is unsurprising that they exhibit extraordinary 

variation in their social organization. Individual taxa are typically described as solitary, 

gregarious, or subsocial. We structure this chapter around those categories, treating 

each in turn, with the caveat that this simplistic pigeonholing masks the head-banging 

vexation we encountered in attempting to classify the social heterogeneity present. Cockroaches 

that live in family groups are a rather straightforward category, and domestic 

pests and a number of cave-dwelling species are without a doubt gregarious. For a variety 

of reasons many others elude straightforward classification. First, the majority of 

cockroaches are unstudied in the field, and the nature and frequency of social interactions 

have been specified in few species. With perhaps a score of exceptions, our concept 

of cockroach social organization is largely based on anecdotal evidence and brief observations 

noted during collection expeditions for museums. Second, cockroaches are often 

assigned social categories without specifying the employed criteria, and the terms describing 

their social tendencies have been used in a vague or inconsistent manner 

(discussed below). Third, evidence to date suggests that sociality in Blattaria is not as 

straightforward as it is in many insects. There is considerable spatial and temporal variation 

in social structure, influenced by, among other factors, the age and sex of the insects, 

environmental condition, physiological state, population density, and harborage 

characteristics. Fourth, many cockroaches are nocturnal and cryptic; consequently even 

those that live in laboratories can be full of surprises. Parental feeding behavior was only 

recently observed in Gromphadorhina portentosa, a species commonly kept in homes as 

pets, in laboratories for experiments, and in museums for educational purposes (Perry 

and Nalepa, 2003). Fifth, even closely related species can vary widely in social proclivities. 

The German cockroach Blattella germanica is strongly gregarious; it has been the test 

subject of the vast majority of studies on cockroach aggregation behavior. Its closely re- 

131

lated congener B. signata, however, is apparently solitary 

(Tsai and Lee, 2001). Sixth, laboratory data can conflict 

with field descriptions. One example: studies on Schultesia 

lampyridiformis reared for 20 yr in the laboratory suggest 

that females use aggression to disperse nymphs after 

hatch (Van Baaren and Deleporte, 2001; Van Baaren et al., 

2003). In the field (Brazil), however, Roth (1973a) found 

adults and nymphs living together in birds’ nests. One 

nest contained 4 males, 8 females, and 29 nymphs, and 

other cockroach species were also present. Lastly, the division 

of species into group living and solitary categories 

is largely artificial in any case because most animal species 

are in an intermediate category, found in association with 

conspecifics at certain times of their lives, but not others 

(Krause and Ruxton, 2002). 

These issues, and others, have bearing on phylogenetically 

based comparative analyses of cockroach social behavior. 

While these can be powerful tools for generating 

and testing ideas about the links between behavior and 

ecology, attempts to map social characteristics onto 

cladograms of cockroach taxa are premature. We are still 

early in the descriptive phase of cockroach social behavior, 

and unresolved phylogenies in many cases preclude 

meaningful comparative study. Some general trends are 

detectable and will be discussed below. 

SOLITARY COCKROACHES 

Currently, few cockroach species are convincingly classified 

as solitary, that is, leading separate lives except for a 

brief period of mating. One category of loners may be 

those cockroaches adapted to deep caves. Although they 

may cluster around food sources, troglobites are typically 

solitary animals, have wide home ranges, and meet only 

for mating (Langecker, 2000). The blattellid Phyllodromica 

maculata is considered solitary, as juveniles do not 

aggregate, nor are they attracted to filter paper contaminated 

by conspecifics (Gaim and Seelinger, 1984). Paratemnopteryx 

couloniana was called “relatively solitary” 

by Gorton (1979), but without statement of criteria. 

Thanatophyllum akinetum was described as solitary by 

Grandcolas (1993a). The insects spend much of their 

time motionless and flattened against dead leaves on the 

forest floor in French Guiana. Laboratory tests support 

the observation that individuals actively distance themselves 

from conspecifics (Van Baaren and Deleporte, 

2001). A solitary, cryptic lifestyle is thought to allow them 

to escape detection by army ants (Grandcolas, 1998). 

Nonetheless, the female broods offspring for several 

hours following hatch, which is a subsocial interaction, 

albeit short term, between a mother and her offspring. 

Lamproblatta albipalpus was described as solitary by Gautier 

et al. (1988), but considered “weakly gregarious” by 

Gautier and Deleporte (1986). Males and females of this 

species are found together in resting sites, but their bodies 

are not in direct contact. Even strongly gregarious 

cockroaches, however, can be separated in space within a 

shelter under certain environmental conditions, for example, 

high relative humidity (Dambach and Goehlen, 

1999). 

AGGREGATIONS: WHAT CRITERIA? 

A variety of nonexclusive criteria have been used to delineate 

cockroach aggregation behavior. These include 

their arrangement in space (are they in physical contact?), 

mechanisms that induce grouping (is a pheromone involved?), 

and the outcome of physical proximity (do 

group effects occur?). Aggregations have been described 

as mandatory, nonobligatory, strong, weak, and loose, 

without further detail. To most entomologists, mutual 

attraction is considered the primary criterion of aggregation 

behavior (Grassé, 1951; Sommer, 1974); group 

membership involves more than co-location, with individuals 

behaving in ways that maintain proximity to 

other group members. In practice, the distinction is not 

easily made, because in most cases both environmental 

and social influences play a role (Chopard, 1938). Many 

cockroaches predictably seek dark, humid, enclosed 

spaces as shelter, and live in close association with nutritional 

resources. The functional basis of a nonrandom 

distribution is especially vague for the vast majority of 

cockroaches regarded as crevice fauna: those found in 

small groups in small shelters, for example, under logs, in 

leaves, under stones, under loose bark. Eickwort (1981) 

suggested testing aggregation behavior by supplementing 

the resources of a group to see if it results in dispersion of 

the insects. Tsuji and Mizuno (1973) and Mizuno and 

Tsuji (1974) gave Periplaneta americana, P. fuliginosa, P. 

japonica, and B. germanica excess harborage and found 

that while adults and older nymphs shelter individually, 

young nymphs seek conspecifics. The results are difficult 

to interpret, because all these test species are commonly 

found in multigenerational aggregations. 

What, then, are necessary and sufficient criteria for 

calling a cockroach gregarious? Are two nymphs found 

together considered a group? Do they have to be the same 

species? Are neonates that remain near a hatched ootheca 

for an hour before dispersing gregarious? What if they remain 

for 3 days? Do aggregation pheromones have to be 

involved? Do the insects have to be touching? The literature 

provides no easy answers. A broad range of variables 

influences the degree to which individuals are positive, 

neutral, or negative with regard to joining a group. These 

include genetics, physiology, informational state, geographic 

region, and the experimental protocol used to test 

132 COCKROACHES

them (Prokopy and Roitberg, 2001). Behavioral observations, 

distance measures, and association patterns in the 

field are all appropriate (Whitehead, 1999), but an explicit 

description of the criteria used in arriving at a social 

description is the logical first step. 

Aggregations:Two Subdivisions 

We divide cockroach aggregations into two categories, on 

the basis of the mechanism by which they are formed: cohort 

aggregations and affiliative aggregations. Cohort 

groups are formed by the non-dispersal of neonates after 

the hatch of an ootheca, and represent kin groups. 

Whether a cohesive sib group results in a cohort aggregation 

or is incorporated into an affiliative aggregation depends 

on the oviposition behavior of the female. The 

placement of an ootheca in an area remote from conspecifics 

by an oviparous female, or oviposition by a solitary 

ovoviviparous female will result in a group comprised 

solely of siblings. There are currently few reports 

of this kind of aggregation. In Lanxoblatta emarginata, 

group size is the mean brood size or slightly less, suggesting 

that in this case, aggregation of nymphs results from 

non-dispersal of a sib group (Grandcolas, 1993a).We suspect 

that some species of forest cockroaches whose 

nymphs live in the leaf litter form cohort aggregations. 

Affiliative aggregations are multigenerational groups that 

may include all developmental stages and both sexes. 

They are fluid societies formed by both the incorporation 

of cohorts of nymphs hatched into the group and by 

immigration. No genetic relationships are implied for 

affiliative aggregations, but they are not ruled out. Cockroaches 

that are urban pests form affiliative aggregations, 

and, along with cave cockroaches, are the best characterized 

in terms of gregarious behavior. 

Relatedness within Groups 

A key issue to address in the analysis of any social behavior 

is the degree of relatedness of group members; in 

cockroaches the variation is considerable. At one end of 

the spectrum, cockroach aggregations are not always 

species specific (Table 8.1). No overt agonistic encounters 

are observed in mixed-species groups, but, given the 

choice, individuals will usually associate with conspecifics 

(Brossut, 1975; Rust and Appel, 1985). Blatta orientalis 

and B. germanica mixed in the laboratory soon form segregated 

groups (Ledoux, 1945). Initially separated taxa, 

however, may eventually mingle if their habitat requirements 

coincide. Everaerts et al. (1997) placed two closely 

related Oxyhaloinae species, Nauphoeta cinerea and Rhyparobia 

maderae, together in laboratory culture. At first 

they stayed in monospecific groups, but the degree of 

mixing increased with time, and the taxa were randomly 

distributed by the fifth day. While intraspecific grouping 

in cockroaches should be considered the general rule, 

conditions of high density or scarcity of resources, such 

as suitable harborage or pockets of high humidity, may 

result in mixed groups. Mixed-species social groups also 

are reported from birds, hoofed mammals, primates, and 

fish, and these typically display gregarious behavior similar 

to that seen in single-species groups (Morse, 1980). 

Although there are no available data on the relatedness 

of individuals in natural aggregations, populations of B. 

germanica within a building are more closely related than 

populations between buildings (C. Rivault, pers. comm. 

to CAN). There are also indications that aggregations are 

cohesive relative to other groups of the same species. In 

B. germanica almost no mixing of aggregations occurs, 

even if several are in close proximity (Metzger, 1995); 

mark-recapture studies show that only 15% of the animals 

left their initial site of capture (Rivault, 1990). In the 

cave cockroach Eublaberus distanti, 90% of individuals 

remained in the same group during a 30-day period (R. 

Brossut in Schal et al., 1984). Site constancy is also known 

in P. americana (Deleporte, 1976; Coler et al., 1987). It is 

Table 8.1. Examples of mixed-species aggregations in 

cockroaches. Additional examples are given in Roth 

and Willis (1960). 

Species Harborage Reference 

Periplaneta americana, In stumps, under Dozier (1920) 

Eurycotis floridana bark, in corded 

wood 

P. americana, Blatta In cupboard of Adair (1923) 

orientalis, Blattella home 

germanica 

Schizopilia fissicollis, Under bark Grandcolas (1993a) 

Lanxoblatta 

emarginata 

Schultesia In bird’s nest Roth (1973a) 

lampyridiformis, 

Chorisoneura sp., 

Dendroblatta 

onephia 

B. germanica, In cracked tele- Appel and Tucker 

P. fuliginosa, phone pole (1986) 

P. americana 

Aglaopteryx diaphana, In bromeliads, Hebard (1917) 

Nyctibora laevigata, Jamaica 

Cariblatta insularis 

Variety of combinations: In sewers Eads et al. (1954, 

Blatta orientalis, 

pers. comm. to 

P. americana, LMR) 

P. fuliginosa, 

Parcoblatta spp. 

SOCIAL BEHAVIOR 133

unclear, however, whether the insects are faithful to the 

group, to the physical location, or both. 

Group Size and Composition 

The size of a cockroach aggregation is ultimately controlled 

by its resource base. If food and water are adequate, 

the surface area of undisturbed dark harborage 

limits population size (Rierson, 1995). Favorable habitats 

can result in enormous populations. Roth and Willis 

(1957), for example, cite a case of 100,000 B. germanica in 

one four-room apartment. As with many other characteristics 

of urban and laboratory cockroaches, however, 

high population size and the tendency to form large aggregations 

are not typical of cockroaches in general. Although 

species that inhabit caves often live in large 

groups, individuals of most species are not at all crowded 

in nature. In Hawaii, aggregations of Diploptera punctata 

in dead dry leaves consisted of 2–8 adults, together with 

5–8 nymphs (WJB and L. Kipp, unpubl. data). Researchers 

who study agonistic or mating behaviors of 

cockroaches in the laboratory are invariably amazed 

when they are unable to observe these activities in the 

field. Small groups of cockroaches are sometimes observed 

feeding and pairs may be seen copulating, but 

never in high numbers (Bell, 1990). In one 3-yr field study 

of cockroach behavior, only four instances of agonistic 

behavior were recorded, while in laboratory cages agonistic 

behavior occurred nearly continuously among 

males (WJB, unpubl. obs.). 

Age- and sex-related variation in grouping tendencies 

are commonly reported in cockroaches (Gautier et al., 

1988) and are no doubt related to the mating system and 

age-dependent fitness biases unique to a species or habitat. 

In most tested cockroaches the early instars have the 

strongest grouping tendencies, and in some they are the 

only stages that display gregarious behavior (e.g., Hafez 

and Afifi, 1956). All developmental stages are found in aggregations 

of B. germanica and P. americana, but young 

nymphs have the greatest tendency to remain in tight 

groups (Ledoux, 1945; Wharton et al., 1967; Bret et al., 

1983; Ross and Tignor, 1986b). At hatch, neonates maintain 

a distance from each other, but aggregate as soon as 

the exoskeleton has hardened (Dambach et al., 1995). The 

gregarious behavior typical of young cockroaches is retained 

into later developmental stages in some species. 

Exceptions lie among the cave cockroaches, where older 

insects may show the strongest grouping tendencies; 

these differences appear related to habitat stratification. 

Adults and older nymphs are typically found aggregated 

on the walls of caves or hollow trees, utilizing crevices if 

present, and young nymphs burrow in guano or litter on 

the substrate (e.g., Blaberus colloseus, Blab. craniifer, Blab. 

giganteus, Eublaberus posticus) (Brossut, 1975; Farine et 

al., 1981; Gautier et al., 1988). Nonetheless, Darlington 

(1970) found that young nymphs of Eub. posticus aggregate 

strongly, but they do so independently of older 

stages, and aggregation pheromone is produced by all developmental 

stages of both Eub. distanti and Blab. craniifer 

(Brossut et al., 1974). Laboratory assays seldom take 

into account the habitat preferences of different stages, 

and we know nothing of the social tendencies of young 

cave cockroaches while under organic debris. Age-related 

distributional differences are known within the large 

affiliative aggregations typical of pest cockroaches. Young 

B. germanica typically cluster in the middle of the aggregation 

(Rivault, 1989). Fuchs and Sann (1981, in Metzger, 

1995) found that first- and second-instar B. germanica 

create small independent aggregations and do not mingle 

with older conspecifics until the third instar. 

There is a complex relationship between sex ratio, sexual 

status, and grouping behavior in affiliative aggregations. 

Ledoux (1945) noted that male nymphs of B. 

germanica showed significantly stronger aggregation tendencies 

than groups of females. Adult females of this 

species have the most influence on group composition, 

but these effects are moderated depending on the demographics 

of the group in question (Bret et al., 1983). The 

reproductive status of females was a factor, with gravid females 

promoting the strongest grouping behavior. The 

maturity of the egg cases carried by females was also 

influential. Adult males typically show little gregariousness 

and spend the least amount of time in shelters. The 

loss of gregarious behavior in males typically coincides 

with sexual maturity and the onset of competition for 

mates (Rocha, 1990). 

An examination of group composition in the cockroaches 

listed by Roth and Willis (1960) indicates that aggregations 

of lesser known species in several cases do not 

contain adult males. The basic unit of some affiliative aggregations 

appears to be the uniparental family: groups of 

mothers together with their offspring. Species mentioned 

include females and young of Ectobius albicinctus found 

beneath stones (Blair, 1922), of Polyphaga aegyptica and 

Polyp. saussurei found in rodent burrows (Vlasov, 1933; 

Vlasov and Miram, 1937), and of Arenivaga grata collected 

from guano in bat caves (Ball et al., 1942). There 

are also occasional reports of cockroach aggregations 

consisting entirely of females, for example, Arenivaga erratica 

in burrows of kangaroo rats (Vorhies and Taylor, 

1922), and aggregated females and dispersed or territorial 

males in Apotrogia sp. ( Gyna maculipennis) (Gautier, 

1980). 

Nothing is known about the immigration of unaffiliated 

cockroaches into established conspecific groups. 

Discrete aggregations collected in the field often mix to- 

134 COCKROACHES

gether freely in the laboratory (e.g., Panesthia cribrata— 

O’Neill et al., 1987), but this is quite different from a solitary 

insect attempting to join an established group under 

natural conditions. When two isolated young nymphs of 

P. americana are placed in contact with each other, they 

undergo a “ritual of accommodation” which may become 

aggressive (Wharton et al., 1968). Behaviors include 

“sampling” each other’s deposited saliva with palpi or antennae, 

stilting, tilting their bodies, bending their abdomens, 

antennal fencing, leg strikes, and biting. The decision 

to accept new members into the aggregation can be 

important when changing ecological conditions (e.g., 

food availability) alter the relationship between group 

size and fitness (Giraldeau and Caraco, 1993). 

Choosing Shelter 

Cockroaches use a variety of criteria in selecting harborage 

sites. In general, cockroaches orient to sheltered sites 

near food and water, and will remain true to a site as long 

as both are adequate (Ross et al., unpubl., in Bret et al., 

1983; Rivault, 1990). Both the texture (Berthold, 1967) 

and orientation of surfaces (Bell et al., 1972) and the size 

of the harborage (Berthold and Wilson, 1967; Mizuno 

and Tsuji, 1974) are influential. Groups of cockroaches 

may segregate by body size, depending on the height of 

available space (reviewed by Roth and Willis, 1960). Small 

nymphs in the absence of older conspecifics prefer narrower 

crevices than do adults; however, they prefer larger 

harborages if other cockroaches are present, indicating 

that social stimuli supersede harborage height preferences 

(Tsuji and Mizuno, 1973; Koehler et al., 1994). Aggregation 

behavior of young nymphs is more pronounced 

in open areas than in shelters, suggesting that 

they may satisfy their thigmotactic tendencies with each 

other when the physical environment is devoid of tactile 

stimuli (Ledoux, 1945). 

Pheromones 

Pheromones rule the social world of cockroaches. The 

chemical repertoire includes both contact pheromones 

and volatiles, and these function as sex pheromones, attractants, 

arrestants, dispersants, alarm pheromones, trail 

pheromones, and mediators of kin recognition. Chemical 

stimuli help orchestrate cockroach aggregation behavior, 

and have been studied primarily for their potential 

in pest management. 

Oviposition Pheromones 

The location of first instars within their habitat is largely 

determined by the oviposition behavior of females, who 

tend to deposit their eggs near resources. Female Periplaneta 

brunnea, for example, generally glue their oothecae 

near a food supply (at least they do in 1 gal battery 

jars) (Edmunds, 1957). There is some evidence to suggest, 

however, that, like locusts (Lauga and Hatté, 1977; Loher, 

1990), some cockroaches may employ oviposition pheromones. 

These serve to either convene gravid females in 

certain locations for egg laying, or attract them to sites 

where conspecifics have previously deposited oothecae. 

Edmunds (1952) found 184 oothecae of Parcoblatta sp. 

deposited in close proximity under tree bark. Similarly, 

oothecae of Supella longipalpa were found in clusters by 

Benson and Huber (1989). The authors observed ovipositing 

females deposit a drop of “genital fluid” on 

oothecae, and suggested that it contains a pheromone 

that attracts other females. Gravid females of B. germanica 

generally do not leave the harborage (Cochran, 

1983b); consequently, first instars hatch into an aggregation 

(Rivault, 1989; Koehler et al., 1994). Stray females, 

however, may actively seek aggregations for oviposition. 

Escaped females of B. germanica in laboratory colonies 

laid their oothecae near a group of conspecific nymphs 

(Ledoux, 1945). 

Aggregation Pheromones? 

Enormous effort has been dedicated to localizing and 

characterizing the aggregation pheromone of pest cockroaches. 

The results, however, are still equivocal. Ledoux 

(1945) first proposed that aggregation in cockroaches was 

the result of mutual attraction of a chemical nature, and 

Ishii and Kuwahara (1967, 1968) identified fecal material 

as the source of the cue. Riding the wave of pheromone 

research during the 1960s, these authors dubbed the fecal 

chemical “aggregation pheromone.” They suggested that 

it originates in the rectal pad cells and that it is applied to 

fecal pellets as they are being excreted. Cuticular waxes 

apparently absorbed the fecal pheromone also, as ether 

washings of the abdomen had higher activity than ether 

washings of other parts of the body. More recent work has 

identified more than 150 volatile and contact chemicals 

from German cockroach fecal pellets (Fuchs et al., 1985, 

in Metzger, 1995; Sakuma and Fukami, 1990). The attractiveness 

of individual components depends not only 

on the type of extraction used, but also the biological assay 

used to test them (reviewed by Dambach et al., 1995), 

and the stock or population of B. germanica used as test 

subjects. Mixtures of fecal compounds are generally more 

effective than single components (Scherkenbeck et al., 

1999). Cuticular wax may be attractive independent of 

any chemicals absorbed from excretory material. Rivault 

et al. (1998) found that cuticular hydrocarbons alone, 

from any part of the body, can elicit aggregation behavior. 

Fecal chemicals seem to function initially as short- 

SOCIAL BEHAVIOR 135

Table 8.2. Aggregation of cockroach nymphs on filter paper conditioned with the feces of other 

cockroach species. Six to eight trials were performed with each combination using 20 nymphs per 

run. Plus-signs represent significant aggregation to conditioned paper as compared to controls. 

From Bell et al. (1972). 

Species conditioning papers 

Nymph species P. am. B.o. P.p. E.p. B.d. B.f. 

After 20 min 

P. americana 

Blatta orientalis 

Parc. pennsylvanica 

Eub. posticus 

Blab. discoidalis 

Byr. fumigata 

After 12 hr 

P. americana 

Blatta orientalis 

Parc. pennsylvanica 

Eub. posticus 

Blab. discoidalis 

Byr. fumigata 

range attractants (Ishii and Kuwahara, 1967; Bell et al., 

1972; Roth and Cohen, 1973), then as arrestants (Burk 

and Bell, 1973). Nymphs halt their forward progress 

when they encounter a filter paper contaminated with feces; 

the response, however, is not strictly species specific 

(Bell et al., 1972; Roth and Cohen, 1973). Cockroaches 

prefer substrates contaminated by feces of their own 

species, but will aggregate on surfaces contaminated by 

distant relatives (Table 8.2). Periplaneta americana was attracted 

to paper contaminated by all species tested, and 

after 12 hr, Parcoblatta pennsylvanica was attracted to 

none, not even their own. Locomotor inhibition is enhanced 

by social interaction between assembled individuals; 

a nymph is more likely to stop on feces-contaminated 

filter paper if one or more nymphs are already in 

residence. Young nymphs are most responsive to the 

chemical cues, adults are intermediate, and middle instars 

the least (Bret and Ross, 1985; Runstrom and Bennett, 

1990). Experience matters; nymphs that hatch in an aggregation 

are more likely to aggregate (Dambach et al., 

1995). 

The evidence suggests that the fecal substances that 

elicit aggregation behavior in cockroaches, then, are not 

pheromones in the classic sense, but a functional category 

of behavior-eliciting chemicals (Brossut, 1975). 

Their origin is unclear, they are poorly defined, and they 

lack specificity. Pheromones are, however, clearly implicated 

in two species, Blab. craniifer and Eub. distanti, 

where the origin of the intraspecific attractant has been 

traced to the mandibular glands (Brossut et al., 1974; 

Brossut, 1979). In these cockroaches the pheromone is 

secreted by all individuals at all times except during the 

molting period. The insects are unattractive from 72 hr 

before to 24 hr after ecdysis (Brossut et al., 1974; Brossut, 

1975). This inactive period occurs because the mandibular 

gland is lined with cuticle (Noirot and Quennedy, 

1974), which is shed along with the rest of the exoskeleton 

during molt. 

Proximate Mechanisms: 

How Do They Aggregate? 

If specific pheromones are not involved in many species, 

how do groups form? Aggregation in cockroaches is generally 

mediated by visual, acoustic, tactile, and/or olfactory 

stimuli (Grassé, 1951). The complication is that these 

often are not the only causes. Environmental factors, including 

light (Gunn, 1940), temperature (Gunn, 1935), 

and air movement (Cornwell, 1968) also play an important 

role. Humidity is a factor, although the degree to 

which it exerts an influence may be species specific (Roth 

and Willis, 1960). In some cockroaches, the lower the 

humidity, the stronger the tendency to aggregate (Sommer, 

1974; Dambach and Goehlen, 1999). Response to 

these, as well as other environmental stimuli, results in 

the initial selection of a harborage, which is consequently 

136 COCKROACHES

marked with bodily secretions (Pettit, 1940); these then 

help mediate immigration into the group. In laboratory 

tests, 82% of B. germanica choose harborages previously 

inhabited by conspecifics (Berthold and Wilson, 1967). 

As the size of an aggregation increases, the collective signal 

of the mass should serve as an increasingly more powerful 

attractant to unassociated individuals. Blattella germanica 

will migrate from a less to a more colonized 

refuge; new refuges are colonized stepwise, with males 

(Denzer et al., 1988) or mid-size nymphs (Bret and Ross, 

1985) as the first to arrive. 

Kavanaugh (1977) suggested three mechanisms by 

which a group may assemble: (1) independent, individual 

responses to environmental gradients, leading to aggregation 

in an abiotically optimum location; (2) individual 

response to stimuli provided by other individuals, 

leading to group formation at a common location; (3) 

some combination of the two. Cockroaches, like many 

other animals, appear to employ the third mechanism, 

with the first and second involved sequentially. This approach 

was recently formalized by Deneubourg et al. 

(2002) and Jeanson et al. (2005). These authors conclude 

that cockroach aggregations are self-organized systems, 

resulting from interactions between individuals following 

simple rules based on local information. First, similar 

species-specific responses to the physical environment 

increase the probability that cockroaches converge in the 

same vicinity. Positive feedbacks and the modulation of 

individual behavior dependent on the proximity of conspecifics 

then result in group formation. Short-range 

volatiles, contact chemicals, physical contact, alterations 

in local microclimate, and perhaps sonic communication 

(Mistal et al., 2000) may all signal the presence of conspecifics 

and serve as cues for an individual to slow or stop 

locomotion. The response to these cues may be modulated 

by heterogeneities in the environment. Garnier et al. 

(2005) used a group of micro-robots modeled after cockroaches 

to demonstrate that the aggregation process is 

based on a simple set of behavioral rules. The robots were 

not only able to form aggregations, but could also make 

a collective choice when presented with two identical or 

different shelters. These broader approaches to cockroach 

aggregation behavior help account for much of the ambiguity 

in the literature on the subject, and aid in integrating 

cockroaches into the existing literature on grouping 

behavior in other animal systems. 

Ultimate Causes: Why Do They Aggregate? 

In cockroaches, gregarious behavior has a wide range of 

potential benefits, ranging from the simple advantage of 

safety in numbers, to group effects that have physiological 

and life history consequences. There are, however, no 

inherent advantages to group living, and the opposite is 

often true. Group members compete for food, shelter, and 

mates, and may burden each other with diseases and parasites 

(Alexander, 1974). It is reasonable to assume that 

aggregation in any animal involves both positive and negative 

components, and that observed social groups are the 

result of the balance of the two (Iwao, 1967; Vehrencamp, 

1983). Fitness biases within a group will vary with species, 

habitat, resources, the age, sex, and reproductive status of 

individuals, and the demographics of the population. 

Aggregations as Environmental Buffer 

Although cockroaches are drawn to shelters with favorable 

temperature and humidity, to some extent cockroach 

aggregates are able to create their own microenvironment. 

Grouped cockroaches may better survive hostile 

dry conditions than loners in at least two species. Dambach 

and Goehlen (1999) found that as a result of respiration 

and diffusion, individuals of B. germanica are each 

surrounded by an envelope of water vapor. These individual 

diffusion fields overlap in aggregated insects, reducing 

net individual water loss. Aggregation behavior 

also reduces water loss in G. portentosa; Yoder and Grojean 

(1997) suggest that it is an adaptation for surviving 

the long tropical dry season of Madagascar. Documentation 

of seasonal changes in social behavior in the field 

would provide added support for this hypothesis. 

Aggregations as Defense 

Although cockroaches are known to have a variety of 

predators and a large number of weapons in their arsenal 

to defend against them, most available information relates 

to predation on individuals. Diurnal aggregations of 

inactive cockroaches, however, have properties that differ 

from active, nocturnal individuals and thus change the 

parameters of the predator-prey interaction. Cues that 

lead predators to prey are multiplied when prey aggregate 

(Hobson, 1978), and the rewards of finding such a concentrated 

source of food are greater. Since cockroaches 

typically assemble in inaccessible places (crevices, leaves, 

hollow logs, under bark, among roots), their apparency is 

presumably low to predators that rely primarily on visual 

cues. Conversely, cockroach aggregations may offer a 

more intense signal to olfactory hunters. At least one parasite 

is known to specialize on cockroach aggregations: 

eggs of the beetle Ripidius pectinicornis are laid in a cluster 

near cockroach aggregations, and early larval stages 

then locate their host (Barbier, 1947). 

The greater number of available sensory receptors in 

an aggregation increases group capacity to sense potential 

predators. There is anecdotal evidence that vigilance 

behavior by peripheral insects may occur in aggregations 

of P. americana. Ehrlich’s (1943) description depicts older 

SOCIAL BEHAVIOR 137

Fig. 8.1 Aggregation of nymphs of Cartoblatta pulchra on a tree trunk in Kenya. The nymphs are 

both aposematically colored and produce a sticky exudate on the terminal abdominal segments. 

Note that heads are oriented toward the center of the group (cycloalexy). Photo courtesy of Michel 

Boulard. 

individuals serving as sentries on the periphery of the 

group; when danger approaches they warn the young 

with body movements. A more realistic interpretation, 

however, may be that members of the aggregation react to 

the evasive maneuvers of the first insect to detect a predator. 

Alarm pheromones have been described in Eurycotis 

floridana (Farine et al., 1997), Therea petiveriana (Farine 

et al., 2002), and cave-dwelling Blaberus spp. (Crawford 

and Cloudsley-Thompson, 1971; Gautier, 1974a; Brossut, 

1983). The emission of these chemicals results in the 

rapid scattering of group members. Predators confronted 

by a confusing welter of moving targets presumably have 

trouble concentrating on individual prey.While defensive 

glands have been described in a large number of cockroaches 

(Roth and Alsop, 1978), whether the secretions of 

these glands function as weapons, signals, or both is in 

many cases untested. Certainly insects that exude or project 

defensive chemicals would benefit from an increase 

in point sources (Vulinec, 1990). One example of this 

type of defensive strategy is known among the Blattaria, 

although it may occur in others (e.g., Dendroblatta sobrina—Hebard, 

1920a). Similar-sized nymphs of Cartoblatta 

pulchra (Blattinae) openly assemble on tree trunks 

in Tanganyika and Kenya (Fig. 8.1). One group, composed 

of 100–150 individuals, formed a rosette larger 

than a human hand. Individuals were polarized, with 

their heads facing the center of the group and their abdomens 

directed radially outward (cycloalexy). A brisk 

movement disperses the cockroaches, and they run into 

crevices in the tree trunk (Chopard, 1938). The insects are 

aposematically colored (black and orange), and each 

nymph displays a thick proteinaceous secretion on the 

terminal abdominal segments. This material originates 

from type 5 tergal glands (Fig. 5.11), is characteristic of 

many oviparous cockroaches (Fig. 4.7), and functions at 

least in part to protect them against ants (Roth and Alsop, 

1978). Most known aposematic cockroach species are 

active during the day in relatively open areas and do 

not form conspicuous aggregations (e.g., Platyzosteria 

ruficeps—Waterhouse and Wallbank, 1967). 

Aggregation and Nourishment 

It has been suggested that one of the main functions of 

gregarious behavior in cockroaches is to signal to unassociated 

individuals the proximity of food and water (Wileyto 

et al., 1984). The addition of extra animals to a 

group, however, results in both added competition for 

food and higher travel costs (Chapman et al., 1995). 

Cockroaches in aggregations are central place foragers; 

they travel from a central location to forage elsewhere, 

then return to shelter. Short-range foraging is the rule in 

B. germanica, and food patches placed near shelters are 

depleted before patches placed farther away (Rivault and 

Cloarec, 1991; Rierson, 1995). When overcrowded, however, 

individuals are known to move more than 10 m 

(Owens and Bennett, 1983). Large, persistent aggregations 

no doubt depend on constant renewal of food resources 

in the vicinity of the harborage, such as dirty 

dishes left in the sink at every meal or the regular deposition 

of guano by bats. 

138 COCKROACHES

In gregarious cockroaches, social facilitation in meeting 

nutritional requirements may occur within two contexts: 

(1) in locating and ingesting food away from the 

harborage, and (2) in the use of food originating from 

conspecifics within the harborage. Individuals of B. germanica 

forage individually but often converge on the 

same sites (Rivault and Cloarec, 1991), suggesting that 

there may be a social component to food finding. Trail 

pheromones (Chapter 9) may facilitate movement from 

the harborage to renewable food sources (a garbage can, 

for example). In habitats where food is unpredictable, 

ephemeral, or patchily distributed, a different form of social 

facilitation may occur. Cockroaches leave behind at 

feeding sites a variety of residues in the form of saliva, 

glandular deposits, and fecal pellets. Feeding sites that are 

“marked” by these residues may be more attractive than 

unmarked food patches because, whether or not foraging 

cockroaches are present, the food has been made “visible” 

by the traffic of conspecifics. If so, cockroaches exhibit the 

simplest form of food-related grouping behavior: local 

enhancement—the act of cueing on conspecifics for food 

information (Mock et al., 1988). Attraction to residues by 

cockroaches would be the chemical equivalent of the visual 

attraction of birds to feeding flocks, or the acoustic 

attraction of bats to the echolocation calls of conspecifics 

(Richner and Heeb, 1995). Cockroaches show a number 

of similarities to rats, which are nocturnal, omnivorous, 

central place foragers that leave chemical cues in the form 

of urine and fecal pellets on resources (food patches, nest 

sites) used by other rats. These residues provide a mechanism 

for social learning and are used in a variety of contexts 

(Galef, 1988; Laland and Plotkin, 1991). 

The benefits of cueing on foraging conspecifics can be 

considerable for young nymphs, who do much better developmentally 

on the same food source if an adult is present. 

The adults seem to “condition” the food in some way, 

either by moistening it, breaking it into smaller pieces, or 

making initial excavations into a tough food item. Both 

Blattella and Supella have been observed depositing saliva 

on food (C. Schal, pers. comm. to WJB), and the development 

of B. germanica nymphs fed whole dog food pellets 

was slower by approximately 43% than nymphs that 

were fed the same food, but pulverized (Cooper and 

Schal, 1992). 

Nutritional advantages of associating with conspecifics 

may also occur within the harborage. The exuvia, corpses, 

feces, exudates, oothecal cases, embryonic membranes, 

and unviable eggs produced by individuals in an aggregation 

as they progress through their lives are fed upon by 

other members of the group (reviewed by Nalepa, 1994) 

(Table 4.6). The presence of this proteinaceous food in 

the harborage may be of particular value to females and 

to young nymphs, as it is these stages that have the highest 

nitrogen requirements. Juveniles in particular may 

benefit from a ready source of high-quality food for several 

reasons. First, young insects have relatively small 

reserves, a high metabolism, and nutritional requirements 

that differ from those of adults (Slansky and 

Scriber, 1985; Rollo, 1986). Second, young cockroaches 

are inefficient in their foraging behavior, and typically do 

not forage far from shelter (Cloarec and Rivault, 1991; 

Chapter 4). Third, as noted above, young nymphs have 

difficulty processing physically hard food. High-quality, 

easily processed food that originates from conspecifics in 

their immediate vicinity may allow the young to pass 

more quickly through the stages during which they are 

most vulnerable. 

Aggregation as a Source of Mates 

In aggregation assays, B. germanica males displayed a 

stronger response to paper conditioned by virgin females 

than to paper conditioned by any other category, whereas 

the female response did not differ when presented with 

the residues of males, females, and juveniles (Wileyto et 

al., 1984). These authors postulated that males unassociated 

with an aggregation may be using the sexual information 

present in the residues to determine the composition 

of a group, and therefore to locate potential mates. 

They concluded that their results were consistent with the 

hypothesis that cockroaches aggregate for the purposes of 

mating. 

Functional separation of aggregation pheromone and 

sexual pheromone is not always possible; sex ratios and 

reproductive status have a complex relationship with aggregation 

behavior in B. germanica (Sommer, 1974; Bret 

et al., 1983). Because females of this species produce a 

nonvolatile as well as a volatile sex pheromone (Nishida 

et al., 1974; Tokro et al., 1993), it is not surprising that 

males respond to their residues. Encounters between potential 

mates are increased by gregarious behavior; newly 

emerged virgin females occur in close proximity to males, 

and sexual communication over long distances is not required 

for mate finding (Metzger, 1995). A virgin, then, 

would not remain one for long in a group that already included 

adult males. The hypothesis of Wileyto et al. 

(1984) would be stronger if wandering males were attracted 

to groups that contained female nymphs in their 

penultimate instar, so that they were already present to 

compete for newly emerged virgins. The argument, however, 

has other flaws. Virgins leave residues regardless of 

whether they are isolated or in a group, and residues in a 

harborage are a mélange of all stages present. It is also unclear 

whether mating takes place within the aggregation 

in free populations. Rivault’s (1989) work suggested that 

prior to the imaginal molt, B. germanica gather in highdensity 

areas in the middle of the aggregate, looking for 

SOCIAL BEHAVIOR 139

sexual partners. However, in a number of species, including 

B. germanica (Nojima et al., 2005), females produce 

volatile sex pheromones, and may move out of the group 

to release them. Females of Blab. giganteus, for example, 

have been observed calling on the outside of a tree that 

contained a large aggregation of conspecifics (C. Schal, 

pers. comm. to WJB). The age, sex, and kinship structure 

of a group will determine the optimal mating strategies 

open to an individual (Dunbar, 1979), and the disadvantages 

of mating in a group should not be ignored. Cockroaches 

typically require 30 min or longer to transfer a 

spermatophore (Roth and Willis, 1954b) and may be subject 

to harassment during that period of time (Chapter 6). 

The suggestion that cockroaches aggregate for the purposes 

of mating, then, may be true in some species or in 

some circumstances, but cannot be applied universally to 

gregarious species. 

Aggregation and Group Effects 

Group effects refer to morphological, physiological, or behavioral 

differences between animals that are grouped 

versus those of the same species that are bereft of social 

contact. The prolongation of the juvenile growth period in 

isolated nymphs is the best-studied group effect in cockroaches, 

occurs in a wide range of species (Table 8.3), and 

is discussed in Chapter 9 in relation to its evolutionary 

connection to caste control in termites. One benefit of accelerated 

development in grouped nymphs is that it moves 

them quickly through one of the riskiest stages of their 

lifecycle. The number of cockroach species examined for 

group effects is extremely limited relative to the number 

of species available for study; especially interesting would 

be a study of those in which nymphs seem to disperse 

shortly after hatch, like Than. akinetum (Grandcolas, 

1993a). Altered juvenile growth rates, however, are not the 

only effect of social interaction. Like some other insects 

that aggregate (reviewed by Eickwort, 1981), molting in 

grouped cockroaches tends to be synchronized (Ishii and 

Kuwahara, 1967). This may be an evolutionary response 

to the threat of cannibalism, as all nymphs are vulnerable 

at the same time, and are incapable of feeding on each 

other until their mouthparts sclerotize. 

Adult cockroaches also show group effects, which are 

Table 8.3. Cockroach species that exhibit group effects on 

development. 

Blattidae: Blatta orientalis, Eurycotis floridana, Periplaneta americana, 

P. australasiae, P. fuliginosa (Willis et al., 1958) 

Blattellidae: Blattella germanica, B. vaga, Supella longipalpa (Willis 

et al., 1958; Izutsu et al., 1970) 

Blaberidae: Diploptera punctata, Eurycotis floridana, Nauphoeta 

cinerea, Pycnoscelus surinamensis, Rhyparobia maderae (Willis et 

al., 1958; Woodhead and Paulson, 1983) 

manifested in physiology and behavior, can be species 

specific, and have a complex influence on reproductive 

success. In B. germanica the presence of another adult has 

an impact on how fast a female reproduces and how much 

she eats, but the former is at least partially independent 

of the latter (Gadot et al., 1989; Holbrook et al., 2000a). 

Komiyama and Ogata (1977) found that isolated females 

of this species deposit a greater number of oothecae than 

group-reared females, but the hatching success of those 

oothecae was considerably lower. In Su. longipalpa, group 

effects were primarily behavioral, and group composition 

rather than isolation was more influential on reproductive 

events. Neither oocyte growth nor calling behavior 

was affected by isolating virgin females, but the onset of 

calling and its diel periodicity were advanced in virgin females 

housed with other virgin females relative to females 

housed with either mated females or males that were unable 

to mate (Chon et al., 1990). Several studies have 

shown that isolated male cockroaches show a decreased 

reaction to female sex pheromone (Roth and Willis, 

1952a; Wharton et al., 1954; Stürkow and Bodenstein, 

1966); the social history of male N. cinerea is known to 

influence the amount of sex pheromone they produce 

(Moore et al., 1995). 

A number of other behavioral effects can be induced 

by isolating cockroaches: the normal flight reaction to 

disturbance may be lost (Hocking, 1958), circadian 

rhythm may be altered (Metzger, 1995), the ability to 

learn may be affected (Gates and Allee, 1933), and activity 

increased (Hocking, 1958) or decreased (Cloudsley- 

Thompson, 1953). Aggressiveness was delayed in isolated 

male N. cinerea (Manning and Johnstone, 1970), but isolation 

increased aggressiveness in Periplaneta (Bell et al., 

1973), The. petiveriana (Livingstone and Ramani, 1978), 

and several cave-dwelling Blaberidae (Gautier et al., 

1988). Raisbeck (1976) found an aggression-stimulating 

substance produced by isolated P. americana that is 

masked or suppressed by “aggregation pheromone” when 

the insects live in groups. 

Aggregations as Nurseries 

Because the costs and benefits of grouping behavior vary 

with species, stage, sex, and environment, there is no simple 

answer to the question of why cockroaches aggregate. 

However, a persistent thread that runs through the previous 

sections relates to gregarious behavior in connection 

to benefits conferred on young nymphs. Regardless of the 

advantages other group members enjoy, affiliative aggregations 

may provide juveniles with all the necessities of 

early cockroach life. The benefits of aggregation behavior 

are often most pronounced in the young, which typically 

suffer the greatest mortality due to desiccation, starvation, 

predators, and cannibals (Eickwort, 1981). The 

140 COCKROACHES

more humid environment that surrounds an aggregate of 

cockroaches may be crucial for young nymphs, as their 

higher respiratory rate and smaller radius of action increases 

their dependence on local sources of moisture 

(Gunn, 1935). The company of conspecifics assures the 

rapid development of nymphs via group effects, and the 

presence of older developmental stages assures a supply 

of conspecific food and an inoculum of digestive microbiota 

(Chapter 5) within the harborage (Nalepa and Bell, 

1997). Away from the harborage, it is possible that trail 

following and local enhancement allow young cockroaches 

access to better food sites than they would find by 

searching on their own. Young nymphs may also pick up 

adaptive patterns of behavior by living in social groups. 

Cockroaches can learn, retain, and recall information; 

this ability is a thorn in the side of urban entomologists 

attempting to develop effective baits for cockroach control 

(Rierson, 1995). 

Costs of Aggregation 

Two noteworthy potential costs of group living in gregarious 

cockroaches are the transmission of pathogens 

(Chapter 5) and the risk of cannibalism. Both the higher 

humidity and the intimate physical association typical of 

aggregations help promote infectious diseases. The cost 

may be direct, resulting in illness or death, or indirect, in 

the form of trade-offs ensuing from increased investment 

in the immune system. Cannibalism is usually a densitydependent 

behavior, in that high population levels may 

decrease the local food supply and lower attack thresholds. 

Injuries also may be more common in dense aggregations, 

resulting in scavenging of the crippled and dead. 

Vulnerable life stages such as oothecae and young or 

molting nymphs may be at risk regardless of group size 

(Dong and Polis, 1992; Elgar and Crespi, 1992). Young 

cockroaches typically suffer the highest mortality of any 

developmental stage (e.g., B. germanica—Sherron et al., 

1982; P. americana—Wharton et al., 1967), in part because 

frequent ecdyses expose nymphs to injury and cannibalism. 

However, if the local food supply adequately 

meets the needs of the older group members, the advantages 

of living in a multigenerational group should outweigh 

the risks for young stages. Cannibalism is relatively 

unstudied in cockroaches (but see Gordon, 1959; Wharton 

et al., 1967), and the information we do have is 

sketchy. Young nymphs are described as the most cannibalistic 

in P. americana (Wharton et al., 1967, Roth, 

1981a), but the behavior is rare in first to third instars of 

B. germanica (Pettit, 1940). While these findings may 

reflect species-specific differences, variation in cannibalistic 

behavior either within or among species may also be 

attributed to laboratory culture under different densities 

or feeding regimens. 

There are additional costs to social behavior, particularly 

when groups become too large. These include increased 

competition for resources, decay in habitat quality, 

and increased attractiveness to predators (Parrish and 

Edelstein-Keshet, 1999). Overcrowded cockroaches may 

exhibit a breakdown in circadian rhythm, enhanced aggression, 

a prolonged nymphal period, supplementary 

juvenile stages, increased mortality, and decreased body 

size (Wharton et al., 1967). Optimal group size is no 

doubt variable and depends on both the taxon in question 

and available resources, but it has been calculated for 

one cockroach. Deleterious effects from crowding begin 

to occur in B. germanica when they exceed a level of 1.2 

individuals/cm 2 in a harborage (Komiyama and Ogata, 

1977). That the net gain of living in a group diminishes 

after the aggregate reaches a certain size is also reflected 

in cockroach chemical communication. The composition 

of the aggregation pheromone in Eub. distanti is known 

to vary with cockroach population density (Brossut, 

1983), and dispersal pheromones have been found in the 

saliva of the German cockroach (Suto and Kumada, 1981; 

Ross and Tignor, 1986a). This pheromone counteracts fecal 

attractants and is most concentrated in the saliva of 

crowded, gravid females. It is thought to function as a 

space regulator within aggregations, force dispersal from 

crowded or otherwise unfavorable conditions, and deter 

cannibalism of young nymphs. Adult males react most 

strongly to the pheromone and are thought to be the 

main target group (Ross and Tignor, 1985; Faulde et al., 

1990). 

PARENTAL CARE 

Most cockroaches show some form of parental care, in 

the broad sense: any form of parental behavior that promotes 

the survival, growth, and development of immatures, 

including the care of eggs or young inside or outside 

the parent’s body, and the provisioning of young 

before or after birth (Tallamy and Wood, 1986; Clutton- 

Brock, 1991). Hinton (1981) considered cockroaches by 

far the largest group of insects that exhibit parental care, 

because he included ovoviviparity and viviparity in the 

category. Regardless of their reproductive mode, cockroaches 

characteristically care for their eggs in elaborate 

ways. In oviparous species, the care includes the production 

of oothecal cases, preparation of oothecal deposition 

sites, concealment of the oothecae, and defense of deposited 

oothecae. In ovoviviparous and viviparous females, 

the embryos are both protected and provisioned 

within the body of the female (Chapter 7). In this chapter 

the scope of parental care will be limited to enhancement 

of post-hatch offspring survival by one or both parents. 

The type of reproduction exhibited by a species 

SOCIAL BEHAVIOR 141

Fig. 8.2 Aposematically colored (dark brown with yellow-orange 

banding) female and nymphs of Desmozosteria grossepunctata 

found under a stone in mallee habitat, Western Australia. 

Photo courtesy of Edward S. Ross; identification by 

David Rentz. 

does, however, influence parent-offspring interactions. 

The majority of cockroaches that exhibit any form of 

post-partition parental care are ovoviviparous; the internal 

retention of the egg case guarantees that the female is 

in the immediate vicinity of nymphs at hatch (Nalepa and 

Bell, 1997). Oviparous females that deposit the egg case 

shortly after its formation depart before neonates emerge 

and may produce several more egg cases before the first 

one deposited hatches. Thus, ovoviviparity results in a 

generational overlap in both time and space, providing 

ample opportunity for brooding behavior. The multiple 

origins of parental care among the ovoviviparous Blaberidae 

suggest that more elaborate forms of parent-offspring 

interactions then evolved from that starting point 

(Nalepa and Bell, 1997). 

In 1983 Breed wrote that very little is known concerning 

post- hatching parent-offspring relationships in cockroaches. 

The situation has improved only slightly since 

that time. The majority of the cockroach species described 

as subsocial are known solely from brief notes 

taken during field collections, documenting females collected 

with offspring from harborages under bark, within 

logs, or under stones (Fig. 8.2). Examples include Poeciloblatta 

sp. (Scott, 1929), Aptera fusca (Skaife, 1954), 

and Perisphaerus armadillo (Karny, 1924). The variety of 

known subsocial interactions in cockroaches, however, is 

among the richest in the insects, and ranges from species 

in which females remain with neonates for a few hours, 

to biparental care that lasts several years and includes 

feeding the offspring on bodily fluids in a nest. 

Brooding Behavior 

The simplest form of parental care in cockroaches is 

brooding, defined as a short-term association of mother 

and neonates. In a number of ovoviviparous blaberids 

(e.g., N. cinerea, Blab. craniifer), young nymphs cluster 

under, around and sometimes on the female for varying 

periods of time after emergence. Most brooding associations 

last less than a day. Although observations of brooding 

behavior are based primarily on laboratory observations, 

Grandcolas (1993a) observed it in Than. akinetum 

in the field. The female was perched on a leaf when first 

instars emerged, and the nymphs aggregated beneath the 

mother’s body for several hours prior to dispersing. In 

cockroaches known to brood, aggregation of the nymphs 

also occurs in the absence of the female; it is not solely 

predicated on all nymphs orienting to their mother as a 

common stimulus (Evans and Breed, 1984). 

It is generally believed that brooding has a protective 

function; it takes several hours for the cuticle of neonates 

to harden, and soft, unpigmented nymphs are at risk from 

ants and cannibalism (Eickwort, 1981). The transfer of 

gut microbiota may also be a factor; short-term contact 

with the female may be necessary so that neonates secure 

at least one fecal meal (Nalepa and Bell, 1997). There are, 

however, no published observations or studies relating to 

the functional significance of brooding. 

We place cockroaches that exhibit brooding behavior 

into a category separate from other subsocial species because 

short-term maternal presence alone defines the behavior. 

Although the female may stilt high on her legs to 

accommodate the nymphs beneath her (e.g., Homalopteryx 

laminata—Preston-Mafham and Preston-Mafham, 

1993; Nauphoeta cinerea—Willis et al., 1958), there are 

currently no reports of active maternal feeding or defense 

in species placed in this group. More detailed study may 

indicate that at least some of these species are subsocial. 

We classified G. portentosa as exhibiting brooding behavior 

(Nalepa and Bell, 1997), when in fact it exhibits shortterm, 

but elaborate parental care. After partition the female 

expels a sizable gelatinous mass that is eaten eagerly 

by neonates (Fig 8.3A) (Perry and Nalepa, 2003). Young 

nymphs then collect under the mother, who is aggressive 

to intruders and hisses at the slightest disturbance (Roth 

and Willis, 1960). 

Subsocial Behavior 

Parental care arose on a number of occasions within the 

ovoviviparous Blaberidae and elsewhere just once, in the 

oviparous Cryptocercidae. One extreme of the subsocial 

range is represented by Byrsotria fumigata. From what we 

currently know of parent-offspring interactions in this 

species, subsociality consists of no more than long-term 

brooding behavior. First instars are able to recognize their 

own mother and prefer to aggregate beneath her for the 

first 15 days after hatch (Liechti and Bell, 1975). More 

142 COCKROACHES

Parental Care on the Body 

In several species of cockroach the protection and feeding 

of young nymphs occurs while the offspring are clinging 

to or attached to the body of the female. A simple 

form of this type of parental care is exhibited by Blattella 

vaga, an oviparous species that carries the ootheca until 

nymphs emerge. The female raises her wings, allowing 

freshly hatched nymphs to crawl under them. They appear 

to feed on material covering her abdomen, then scatter 

shortly afterward (Roth and Willis, 1954b, Fig. 65). 

More complex forms of this behavior are found among 

cockroaches in the Epilamprinae. Females in three genera 

(Phlebonotus, Thorax, and Phoraspis) (Roth, 2003a) have 

an external brood chamber, allowing them to serve as “armoured 

personnel carriers” (Preston-Mafham and Preston-Mafham, 

1993). The tegmina are tough and domeshaped, 

and cover a shallow trough-like depression in the 

dorsal surface of the abdomen, forming a space for protecting 

and transporting the young. The aquatic species 

Phlebonotus pallens carries about a dozen nymphs beneath 

its wing covers (Shelford, 1906b; Pruthi, 1933) (Fig. 

8.4). In Thorax porcellana the maternal behavior lasts for 

about 7 weeks; 32–40 nymphs scramble into the brood 

chamber immediately after hatch and remain there during 

the first and second instars. Their legs are well adapted 

for clinging, with large pulvilli and claws. It is probable 

that nymphs feed on a pink material secreted from thin 

membranous areas on the dorso-lateral regions of the 

fourth, fifth, sixth, and seventh tergites of the mother. The 

mouthparts of first instars are modified with dense setae 

Fig. 8.3 (A) Newly hatched nymphs of Gromphadorhina portentosa 

feeding on secretory material expelled from the abdominal 

tip of the female (note left cercus). A new pulse of the 

material is just beginning to emerge. The oothecal case can be 

seen in the upper-right corner. Image captured from frame of 

videotape, courtesy of Jesse Perry. (B) Four young nymphs of 

Salganea taiwanensis feeding on the stomodeal fluids of the female, 

viewed through glass from below. Note antennae of the 

adult. Photo courtesy of Tadao Matsumoto. 

elaborate forms of subsocial behavior include those 

species in which morphological modifications of the 

nymphs or the female facilitate parental care. Specializations 

of the juveniles include appendages that aid in 

clinging to the female, and adaptations of their mouthparts 

to facilitate unique feeding habits. Some females 

have evolved external brood chambers under their wing 

covers, and others have the ability to roll into a ball, pill 

bug-like (conglobulation), to protect ventrally clinging 

nymphs. Maternal care is the general rule, biparental care 

is recognized only in two taxa of wood-feeding cockroaches, 

and male uniparental care is unknown. 

Fig. 8.4 Female of Phlebonotus pallens carrying nymphs beneath 

her tegmina. After Pruthi (1933). 

SOCIAL BEHAVIOR 143

Fig. 8.5 Perisphaerus sp. from the Philippines. (A) Ventral view of adult female from Mt. Galintan; 

arrows indicate orifices between coxae. (B) Orifices (arrows) between coxae. (C) Head of 

probable first instar that was attached to an adult female. (D) Head of probable second instar that 

was attached to an adult female. From Roth (1981b); photos by L.M. Roth. 

on the maxillae and labium, suggesting that they feed on 

a liquid diet. Midguts of young instars are filled with a 

pink material rather than the leaf chips they eat when 

older (Reuben, 1988). Jayakumar et al. (1994) and Bhoopathy 

(1998), however, suggest that young instars of this 

species may use a long, sharp mandibular tooth to pierce 

the tergites of the female and withdraw nourishment. 

First-instar nymphs removed from the mother do not 

live. Second-instar nymphs begin to make short forays 

from their maternal dome home to feed on dry leaves, 

and will survive if removed from their mother. 

Among the Perisphaeriinae there are two recorded 

cases of nymphs clinging to the ventral surface of the 

mother for protection and nutrition. Nymphs of Perisphaerus 

cling to the female for at least two instars (Roth, 

1981b). There are 17 species in this genus, but they are 

known almost exclusively from the study of museum 

specimens. First-instar nymphs are eyeless and have an 

elongate head and specialized galeae that suggest the intake 

of liquid food from the mother. There are four distinct 

orifices on the ventral surface of the female, with one 

pair occurring between the coxae of both the middle and 

hind legs (Fig. 8.5). Females have been collected with the 

mouthparts of a nymph inserted into one of these 

orifices; the “proboscis” of nymphs is 0.3 mm wide, about 

the same width as the intercoxal opening. The food of the 

nymphs may be glandular secretions or possibly hemolymph. 

The female can roll up into a ball with her 

144 COCKROACHES

clinging nymphs inside, rendering both the female and 

the nymphs she surrounds relatively impervious to attacks 

by ants (Fig. 1.11B). At least nine nymphs may be 

enclosed when the female assumes the defensive position. 

Other genera with the ability to conglobulate (e.g., 

Pseudoglomeris) may also exhibit this type of parental 

care. A similar defensive behavior occurs in species where 

the female “cups” her underside against a hard substrate 

(Fig. 8.6). In Trichoblatta sericea, well-developed pulvilli 

and claws of first-instar nymphs allow them to cling to the 

underside of the female for the first 2 to 3 days after hatching. 

The female secretes a milky fluid from her ventral 

side, which probably serves as food for the nymphs. 

Neonates isolated from their mother did not survive past 

the second instar (Reuben, 1988). 

Parental Care in a Nest or Burrow 

Nests and burrows typically reduce the biological hazards 

of the external environment and reinforce social behavior 

(Hansell, 1993). The structures offer protection from 

natural enemies and act as a buffer against temperature 

and moisture fluctuations. In subsocial cockroaches 

found in nests, one or both parents also actively defend 

the galleries against predators and conspecific intruders. 

Because these cockroaches nest in or near their food 

source (wood, leaf litter), parents can forage without leaving 

or carrying their offspring. Australian soil-burrowing 

cockroaches nest only where their food source is ample 

and forage close to the entrance (Macropanesthia), and 

so are absent from their family for only brief periods of 

time (Rugg and Rose, 1991; Matsumoto, 1992). Females 

Fig. 8.6 Maternal care in an unidentified apterous cockroach 

collected in Namibia, ventral view. The female was clinging to 

a rock, with the elongated edges of the tergites serving to raise 

her venter above the substrate and form a brood covering 

“cup.” The presence of ants (upper-right quadrant) in this field 

photo suggests that the behavior functions to defend young 

nymphs, although it is possible the female also supplies them 

with nutriment. Photo and information courtesy of Edward S. 

Ross. 

with young are quite aggressive (D. Rugg, pers. comm. to 

CAN). 

Biparental care in a nest arose at least twice among 

wood-feeding cockroaches: in the ovoviviparous Panesthiinae 

and in the oviparous Cryptocercidae. These insects 

typically nest in damp, rotted logs, utilizing the 

wood itself as a food source; consequently, the young are 

never left untended. A wood-based diet may warrant the 

cooperation of both parents; wood-feeding has favored 

paternal investment not only in cryptocercids and some 

panesthiines, but also in passalid and scolytid beetles 

(Tallamy and Wood, 1986; Tallamy, 1994). 

Cryptocercus is the only known oviparous cockroach 

with well-developed parental care, and is discussed in 

Chapter 9 in the context of its sister group relationship to 

termites. A recent study found that adult presence has a 

significant effect on offspring growth in families of C. 

kyebangensis (Park and Choe, 2003a), but the relative influence 

of parental care and group effects are yet to be determined. 

In gregarious Periplaneta, for example, single 

nymphs raised with adults grow and develop as rapidly as 

grouped nymphs (Wharton et al., 1968). All studied 

species in the wood-feeding blaberid genus Salganea live 

in biparental families (Matsumoto, 1987; Maekawa et al., 

1999b, 2005). In Sal. taiwanensis, nymphs cling to the 

mouthparts of their parents and take liquids via stomodeal 

feeding (Fig. 8.3B). Removal of neonates from 

parental care results in high mortality; removed nymphs 

that live have a significantly longer duration of the first 

instar (T. Matsumoto and Y. Obata, pers. comm. to CAN). 

Two different social structures have been reported 

for Australian wood-feeding panesthiines: both family 

groups and aggregations. Shaw (1925) reported that both 

Panesthia australis and Pane. cribrata ( laevicollis) live in 

family groups consisting of a pair of adults and nymphs 

in various stages of development. Matsumoto (1988) 

more recently studied Pane. australis, and found that of 

29 social groups collected, the majority were families: 14 

consisted of a female with nymphs, two were a male with 

nymphs, and two were an adult pair with nymphs. 

Groups never contained more than a single adult of either 

sex or an adult pair together with nymphs. The age of 

nymphs in the group ranged widely, however, so it is possible 

that the nymphs in these groups were aggregated individuals 

rather than a sibling group (T. Matsumoto, pers. 

comm. to CAN). The field studies of H. A. Rose (pers. 

comm. to CAN) indicate that neither Pane. australis nor 

any of the other wood-feeding Australian panesthiines 

are subsocial. Rugg and Rose (1984b) and O’Neill et al. 

(1987) found that while adult pairs with nymphs could be 

found in Pane. cribrata (12% of groups), the most commonly 

encountered groups (29%) were harems, consisting 

of a number of adult females, together with a single 

SOCIAL BEHAVIOR 145

adult male and a number of nymphs. A possible reason 

for these discrepancies is that social structure in this 

genus may vary with habitat and population density. 

Harems seem to be common in areas of high population 

density, while family groups are generally found in marginal 

environments, or on the outer fringes of areas with 

high population density (D. Rugg, pers. comm. to CAN). 

Parental Feeding of Offspring 

Like other subsocial insects, the defense of offspring is a 

component of the behavioral repertoire of all cockroach 

species that exhibit parental care. Parents protect offspring 

in a nest, beneath the body, under wing covers, or 

directly attached to the body. A large number of cockroach 

species produce defensive secretions (Roth and Alsop, 

1978) and females with young may be the most likely 

to employ them (e.g., Thorax porcellana—Reuben, 1988). 

More unique among subsocial insects is the variety of 

mechanisms by which cockroach parents are a direct 

source of food to their nymphs. Many species for which 

we have evidence of advanced parental care, as well as viviparous 

and possible ovoviviparous females, see to the 

nutritional needs of their offspring by feeding them on 

bodily fluids (Table 8.4). Parental food may be produced 

internally in a brood sac, expelled in a mass after hatch, 

secreted externally either dorsally or ventrally on the abdomen, 

or produced from either end of the digestive system. 

The materials transferred from parent to post-hatch 

offspring have not been analyzed in any cockroach 

species. The basis of the stomodeal feeding exhibited by 

Salganea (Fig. 8.3B) would be of particular interest, as 

Periplaneta is known to secrete at least two different types 

of saliva in response to stimulation from different neurotransmitters. 

One type of saliva has a dramatically higher 

proteinaceous component than the other (Just and Walz, 

1994). 

Maternal provisioning likely occurs in taxa additional 

to those listed in Table 8.4. Like Gromphadorhina, the 

blaberids Byr. fumigata, Blaberus sp., and R. maderae all 

have glandular cells in the brood sac that may secrete a 

post-hatch meal for neonates (references in Perry and 

Nalepa, 2003). The lateral abdominal tergites in most female 

Perisphaeriinae and in many Panesthiinae of both 

sexes have rows of glandular orifices of unknown function 

(Anisyutkin, 2003). The vast majority of ovoviviparous 

females have yet to be studied while alive. Even if a 

female does not provide bodily exudates, she may facilitate 

offspring feeding in other ways. There are two reports 

that young nymphs of R. maderae accompany their 

mother on nocturnal foraging trips (Séin, 1923; Wolcott, 

1950). 

If the standard diet of a species is one that can be handled 

more efficiently by adults than by juveniles (e.g., 

physically difficult food), then the most efficient way to 

convert it to a form usable by young nymphs may be via 

exudates from a parent. The young are offered a reliable, 

Table 8.4. Parental care in cockroaches where post-hatch offspring are fed on the bodily secretions 

of adults (modified from Nalepa and Bell, 1997). 

Offspring 

Species Subfamily Location Food source 

Perisphaerus sp. Perisphaeriinae Cling ventrally Hemolymph? 4 

Trichoblatta sericea Perisphaeriinae Cling ventrally Sternal exudate 5 

Pseudophoraspis nebulosa Epilamprinae Cling ventrally ? 6 

Phlebonotus pallens Epilamprinae Under tegmina ? 6,7 

Thorax porcellana Epilamprinae Under tegmina Tergal exudate 5 

Gromphadorhina Oxyhaloinae Abdominal tip Secretion from 

portentosa of female brood sac? 8 

Salganea taiwanensis 1 Panesthiinae Mouthparts of Stomodeal fluids 9 

adult 

Cryptocercus punctulatus, Cryptocercinae Abdominal tip Hindgut fluids 10,11,12 

C. kyebangensis 1,2 of adult 

Blattella vaga 2,3 Blattellinae Under tegmina Tergal exudate 13 

1 

Biparental families. 

2 

Oviparous. 

3 

Brief association. 

4 

Roth (1981b). 

5 

Reuben (1988). 

6 

Shelford (1906a). 

7 

Pruthi (1933). 

8 

Perry and Nalepa (2003). 

9 

T. Matsumoto and Y. Obata (pers. comm. to CAN). 

10 

Seelinger and Seelinger (1983). 

11 

Nalepa (1984). 

12 

Park et al. (2002). 

13 

Roth and Willis (1954). 

146 COCKROACHES

easy-to-digest diet, thereby relieving them of the necessity 

of finding and processing their own food. Because the 

mother can meet at least part of the metabolic demands 

of “lactation” from her own bodily reserves, these cockroach 

juveniles are unaffected by temporary shortages of 

food items in the habitat during their phase of most rapid 

growth (Pond, 1983). The cockroach ability to store and 

mobilize nitrogenous materials via symbiotic fat body 

flavobacteria may be the basis for the variety of different 

food materials offered in parental provisioning (Nalepa 

and Bell, 1997, Chapter 5). 

Altricial Development 

After a parental lifestyle evolves, subsequent developmental 

adaptations often occur that reduce the cost of 

care and increase the dependency of offspring (Trumbo, 

1996; Burley and Johnson, 2002). This is a universal 

trend, in that the developmental correlates of parental 

care are similar in both vertebrates and invertebrates. The 

pampered juveniles in these parental taxa are altricial, 

which in young cockroaches is evident in their blindness, 

delicate exoskeleton, and dependence on adults for food 

(Nalepa and Bell, 1997). Neonates of Cryptocercus are a 

good example of altricial development in cockroaches. 

First instars lack compound eyes; eye pigment begins developing 

in the second instar. The cuticle is pale and thin, 

with internal organs clearly visible through the surface of 

the abdomen. Gut symbionts are not established until the 

third instar, making young nymphs dependent on adults 

for food. First instars are small, averaging just 0.06% of 

their final adult dry weight. The small size of neonates is 

associated with the production of small eggs by the female. 

The length of the terminal oocyte is 5% of adult 

length, contrasting with 9–16% exhibited by six other 

species of oviparous cockroaches (Nalepa, 1996). Young 

nymphs of Perisphaerus also lack eyes; in one species at 

least the first two instars are blind (Roth, 1981b). We have 

little information on developmental trends in those 

cockroach species where females carry nymphs. It would 

be intriguing, however, to determine if, like marsupials, 

internal gestation in these species is truncated, with 

nymphs completing their early development in the female’s 

external brood chamber. 

Juvenile Mortality and Brood Reduction 

Overall, insects that exhibit parental care may be expected 

to show low early mortality when compared to nonparental 

species (Itô, 1980). This pattern, however, does 

not seem to apply to the few species of subsocial cockroaches 

for which survivorship data are available. In 

Macropanesthia, mortality is about 35–40% by the time 

the nymphs disperse from the nest at the fifth to sixth instar 

(Rugg and Rose, 1991; Matsumoto, 1992). Both Salganea 

esakii and Sal. taiwanensis incubate an average of 15 

eggs in the brood sac, but average only six nymphs (third 

instar) in young, field-collected families (T. Matsumoto 

and Y. Obata, pers. comm. to CAN). Family size of Cryptocercus 

punctulatus declines by about half during the initial 

stages; a mean of 73 eggs is laid, but families average 

only 36 nymphs prior to their first winter (Nalepa, 1988b, 

1990). These data suggest that neonates may be subject to 

mortality factors such as disease or starvation despite the 

attendance of adults. 

An alternative explanation for high neonate mortality 

in these species is that it represents an evolved strategy for 

adjusting parental investment after hatch (Nalepa and 

Bell, 1997). Unlike other oviparous cockroaches, in Cryptocercus 

the hatching of nymphs from the egg case is not 

simultaneous, but extended in time. Hatching asynchrony 

results in variation in competitive ability within a 

brood, a condition particularly conducive to the consumption 

of young offspring by older siblings (Polis, 

1984). Nymphs of C. punctulatus 12 days old have been 

observed feeding on dead siblings, and attacks by nymphs 

on moribund siblings have also been noted. Age differentials 

within broods may allow older nymphs to monopolize 

available food, leading to the selective mortality 

of younger, weaker, or genetically inferior siblings. Necrophagy 

or cannibalism by adults or older juveniles may 

then recycle the somatic nitrogen of the lower-quality offspring 

back into the family (Nalepa and Bell, 1997). The 

production of expendable offspring to be eaten by siblings 

can be viewed as an alternative to producing fewer 

eggs, each containing more nutrients (Eickwort, 1981; 

Polis, 1981; Elgar and Crespi, 1992). 

The behavioral mechanisms balancing supply (provisioning 

by parents) and demand (begging or solicitation 

by nymphs) are unstudied in subsocial cockroaches. In 

Cryptocercus, adults appear to offer hindgut fluids periodically, 

with juveniles competing for access to them. It is 

probable that, like piglets, nymphs that struggle the hardest 

to reach parental fluids will gain the biggest share. 

Competition for food may be a proximate mechanism for 

adjusting brood size and eliminating runts in other subsocial 

cockroaches as well. Perisphaerus sp. females possess 

just four intercoxal openings, but nine nymphs were 

associated with one of the museum specimens studied by 

Roth (1981b). Sibling rivalry for maternally produced 

food is also observable in G. portentosa and Sal. taiwanensis 

(Fig. 8.3). In Cryptocercus, there is some evidence of 

parent-offspring conflict in the amount of trophallactic 

food that an individual nymph receives. Adults can deny 

access to hindgut fluids by closing the terminal abdominal 

segments, like a clamshell. In the process of doing so 

the head of a feeding nymph is sometimes trapped, and 

the adult attempts to either fling it off with abdominal 

SOCIAL BEHAVIOR 147

Fig. 8.7 Nymphs of Cryptocercus punctulatus cooperatively feeding on a sliver of wood. Photo by 

C.A. Nalepa. 

wagging, or to scrape it off by dragging it along the side 

of the gallery (CAN, unpubl. obs.). 

It should be noted that in Cryptocercus there are cooperative 

as well as competitive behaviors among nymphs 

when procuring food. Wood is not only nutritionally 

poor and difficult to digest, but physically unyielding. 

Like young nymphs in aggregations, early developmental 

stages of Cryptocercus may need the presence of conspecifics 

to help acquire meals when they begin including 

wood in their diet. Nymphs have been observed feeding 

cooperatively on wood slivers pulled free by both siblings 

(Fig. 8.7) and adults (Nalepa, 1994; Park and Choe, 

2003a). 

Cost of Parental Care 

Most cockroaches that exhibit parental care are subject to 

risks associated with brood defense and invest time in 

taking care of offspring. Other costs vary with the form 

and intensity of parental care. Brooding, for example, is a 

small investment on the part of the female in relation to 

potential returns (Eickwort, 1981). In females that carry 

offspring on their bodies, the burden may hinder locomotion 

and thus the ability to escape from predators. Energy 

expended on nest construction can detract from a 

parent’s capacity for subsequent reproduction in those 

species where parental care occurs in excavated burrows. 

Insects that utilize nests may also invest time and energy 

in provisioning and hygienic activities (Tallamy and 

Wood, 1986). Feeding offspring on bodily secretions may 

drain stored reserves otherwise devoted to subsequent 

bouts of oogenesis. The metabolic expenditure may be 

particularly high in wood-feeding species, whose diet is 

typically low in nitrogenous materials. The high cost of 

parental care in Cryptocercus may account for their functional 

semelparity (Nalepa, 1988b), and has been proposed 

as a key precondition allowing for the evolution of 

eusociality in an ancestor they share with termites (Chapter 

9). It is of interest then, that, another wood-feeding 

cockroach (Salganea matsumotoi) that lives in biparental 

groups and is thought to exhibit extensive parental care 

appears to have more than one reproductive episode 

(field data) (Maekawa et al., 2005). 

In insects that do not nest in their food source, providing 

care to young may conflict with feeding opportunities, 

particularly in species whose diet consists of dispersed 

or ephemeral items that require foraging over 

substantial distances. One solution to is to carry one 

brood while gathering nutrients for subsequent brood 

development (Tallamy, 1994). To test this hypothesis, it is 

necessary to determine (1) if females feed while externally 

carrying nymphs, and (2) if females carrying nymphs are 

concurrently developing their next set of eggs, incubating 

eggs in the brood sac, or building reserves for the next 

brood. We found relevant information on two species. A 

Pseudophoraspis nebulosa female caught in the field with 

numerous neonates clinging to the undersurface of her 

abdomen was dissected, and her brood sac was empty 

(Shelford, 1906a). In Tho. porcellana, newly hatched 

nymphs remain in association with their mother for 45 

days. After partition another ootheca is formed in 15 to 

20 days, and gestation takes 45–52 days. There is therefore 

a period of time when the female is both internally 

incubating an ootheca in her brood sac and externally 

carrying nymphs on her back. However, these are sluggish 

insects that remain stationary in the leaves on which they 

148 COCKROACHES

feed (Reuben, 1988). At present, then, too little information 

is available for a fair evaluation of Tallamy’s (1994) 

hypothesis. 

SOCIAL INFLUENCES 

Social behavior in cockroaches, as in other insects (Tallamy 

and Wood, 1986), is largely a function of the type, 

accessibility, abundance, persistence, predictability, and 

distribution of the food resources on which they depend. 

Large cockroach aggregations are found only where food 

is consistently renewed by vertebrates (bats, birds, humans). 

Biparental care is found only in wood-feeding 

cockroaches, whose diet is physically tough, low in nitrogen, 

and digested in cooperation with microorganisms. 

Young developmental stages in both aggregations and 

families rely at least in part on food originating from fellow 

cockroaches. Although predation pressure can alter 

social structure (Lott, 1991), and has been suggested as a 

selective pressure in cockroaches (Gautier et al., 1988), 

data with which we can evaluate its influence are scarce. 

Reproductive mode is unrelated to gregariousness; both 

oviparous and ovoviparous cockroaches aggregate. Subsocial 

cockroaches, however, are almost exclusively ovoviviparous. 

While the costs and benefits of social behavior 

for other developmental stages vary with a wide 

variety of factors, the benefactors in most cockroach social 

systems are young nymphs. Several uniquely blattarian 

characteristics influence cockroach social structure, 

such as the ability to mobilize stored nitrogenous reserves 

and the need for hatchlings to acquire an inoculum of gut 

microbes. Cockroaches also display similarities to not 

only other insect but also to vertebrate social systems 

(e.g., altricial development). They are thus potentially excellent 

models with which to test general hypotheses in 

social ecology. 

SOCIAL BEHAVIOR 149

NINE 

Termites as Social Cockroaches 

Our ancestors were descended in early Cretaceous times from certain kind-hearted 

old cockroaches. 

—W.M. Wheeler, “The Termitodoxa, of Biology 

and Society” (in the voice of a termite king) 

It has long been known that termites (Isoptera), cockroaches (Blattaria), and mantids 

(Mantodea) are closely related (Wheeler, 1904; Walker, 1922; Marks and Lawson, 1962); 

they are commonly grouped as suborders of the order Dictyoptera (Kristensen, 1991). 

Although there is a general agreement on the monophyly of the order, during the past 

two decades the sister group relationships of these three taxa and the position of woodfeeding 

cockroaches in the family Cryptocercidae in relation to termites have been lively 

points of debate (see Nalepa and Bandi, 2000; Deitz et al., 2003; Lo, 2003 for further discussion). 

A variety of factors contribute to obscuring the relationships. First, fossil and 

molecular evidence indicate that these taxa radiated within a short span of time (Lo et 

al. 2000; Nalepa and Bandi, 2000). A rapid proliferation and divergence of the early forms 

would obscure branching events via short internal branches separating clades, instability 

of branching order, and low bootstrap values of the corresponding nodes (Philippe 

and Adoutte, 1996; Moore and Willmer, 1997). Second, heterochrony played a major role 

in the genesis and subsequent evolution of the termite lineage (Nalepa and Bandi, 2000). 

It is notoriously difficult to determine the phylogenetic relationships of organisms with 

a large number of paedomorphic characters (Kluge, 1985; Rieppel, 1990, 1993). Reductions 

and losses make for few morphological characters on which to base cladistic analysis, 

and parallel losses of characters by developmental truncation make it difficult to distinguish 

between paedomorphic and plesiomorphic traits (discussed in Chapter 2). 

Third, cockroaches in the particularly contentious family Cryptocercidae live and die 

within logs and have left no fossil record. Fourth, extant lineages of Dictyoptera represent 

the terminal branches of a once luxuriant tree, with many extinct taxa. Finally, several 

phylogenetic studies of the Dictyoptera have been problematic because of ambiguous 

character polarity, inadequate taxon sampling, and questionable reliability of the 

characters used for phylogenetic inference (for discussion, see Lo et al. 2000; Deitz et al., 

2003; Klass and Meier, 2006). 

The bulk of current evidence supports the classic view (Cleveland et al., 1934; Grassé 

150

Fig. 9.1 Phylogenetic tree of Dictyoptera, after Deitz et al. 

(2003). Mantids branched first, Blattaria is paraphyletic with 

respect to the examined Isoptera (Mastotermitidae, Kalotermitidae, 

Termopsidae), and Cryptocercidae is the sister group 

to termites. The study was conducted utilizing the same morphological 

and biological data base used by Thorne and Carpenter 

(1992), however, polarity assumptions and uninformative 

characters were eliminated, characters, character states, 

and scorings were revised, and seven additional characters were 

added. The tree suggests a single acquisition of both symbiotic 

fat body bacteroids (Blattabacterium) and hindgut flagellates 

within the Dictyoptera. Bacteroids were subsequently lost in all 

termites but Mastotermes; oxymonadid and hypermastigid 

flagellates were lost in the “higher” termites (Termitidae—not 

included in tree). The sister group relationship of Cryptocercus 

and Mastotermes is supported by phylogenetic analysis of fat 

body endosymbionts (Fig. 5.7) and the cladistic analysis of 

Klass and Meier (Fig. P.1). *Blattaria denotes Blattaria except 

Cryptocercidae. 

and Noirot, 1959) that Cryptocercidae is sister group to 

termites. It is not, however, a basal cockroach group as 

proposed by most early workers (e.g., McKittrick 1964, 

Fig. 1). Mantids branched first, with Cryptocercus 

Isoptera forming a monophyletic group deeply nested 

within the paraphyletic cockroach clade (Fig. 9.1; see also 

Fig. P.1 in the Preface and Fig. 5.7). These relationships 

are supported by morphological analysis (Klass, 1995), 

by analysis of morphological and biological characters 

(Deitz et al., 2003; Klass and Meier, 2006), by Lo et al.’s 

(2000) analysis of three genes, and by Lo et al.’s (2003a) 

analysis of four genes in 17 taxa, the most comprehensive 

molecular study to date. The fossil record and the clocklike 

behavior of 16S rDNA of fat body endosymbionts in 

those lineages possessing them indicate that the radiation 

of mantids, termites, and modern cockroaches (i.e., without 

ovipositors) occurred during the late Jurassic–early 

Cretaceous (Vršanský, 2002; Lo et al., 2003a). 

This phylogenetic hypothesis provides a parsimonious 

explanation for several key characters of Dictyoptera. An 

obligate relationship with Oxymonadida and Hypermastigida 

flagellates in the hindgut paunch first occurred 

in an ancestor common to Cryptocercus and termites, and 

was correlated with subsociality and proctodeal trophallaxis 

(Nalepa et al., 2001a). These gut flagellates were subsequently 

lost in the more derived Isoptera (Termitidae). 

Endosymbiotic bacteroids (Blattabacterium) in the fat 

body were acquired by a Blattarian ancestor, or acquired 

earlier in the dictyopteran lineage and subsequently lost 

in mantids. All termites but Mastotermes subsequently 

lost their Blattabacterium endosymbionts (Bandi and 

Sacchi, 2000, discussed below). The phylogenetic hypothesis 

depicted in Fig. 9.1, then, is consistent with a single 

acquisition and a single loss of each of the two categories 

of symbiotic associations. Eusociality evolved once, from 

a subsocial, Cryptocercus-like ancestor. 

Lo (2003) offers two reasons for exercising some caution 

in the full acceptance of this phylogenetic hypothesis. 

First, for two of the genes that support the sister group 

relationship of Cryptocercus and termites, sequences are 

unavailable in mantids because they possess neither: 16S 

rDNA of bacteroids and those coding for endogenous cellulase. 

Second, because cockroach classification is in flux 

and taxon sampling is still relatively poor, additional data 

may alter tree topology. One possibility is that mantids 

may be the sister group of another lineage of cockroaches, 

which would render modern cockroaches polyphyletic 

with respect to both termites and mantids (Lo, 2003). 

Based on their examination of fossil evidence, Vršanský 

et al. (2002) suggested that contemporary cockroaches 

may be paraphyletic with respect to Mantodea as well as 

Isoptera. 

The ancestor common to all three dictyopteran taxa 

was almost certainly cockroach-like (Nalepa and Bandi, 

2000). Cockroaches are the most generalized of the orthopteroid 

insects (Tillyard, 1919), while Mantodea are 

distinguished by apomorphic characters associated with 

their specialized predatory existence. Both cockroaches 

and termites have predatory elements in them, although 

in termites it is probably limited to conspecifics (i.e., cannibalism). 

Mantids have short, straight alimentary canals 

(Ramsay, 1990), and like other predators (Moir, 1994), 

they neither have nor require gut symbionts. Elements of 

certain mantid behaviors are evident among extant cockroaches, 

such as the ability to grasp food with the forelegs 

(Fig. 9.2), and in some species, assumption of the “mantis 

posture” during intraspecific fights. A cockroach combatant 

may elevate the front portion of the body, raise the 

tegmina to 60 degrees or more above its back, fan the 

wings, and lash out with the mandibles and prothoracic 

legs (WJB, pers. obs.). Mantids, however, tend to lead 

open-air lives (Roy, 1999), and although some are known 

to guard egg cases, the suborder as a whole is solitary 

(Edmunds and Brunner, 1999). All extant termites, on the 

other hand, live in eusocial colonies, and have highly derived 

characters related to that lifestyle. There is little 

TERMITES AS SOCIAL COCKROACHES 151

doubt that the evolution of eusociality was the event that 

rocketed the termite lineage into a new adaptive zone. A 

correlate of universal and complex social behavior among 

extant termites, however, is the difficulty in developing 

models of ancestral stages based on characters of living 

Isoptera. Because the best-supported phylogenetic hypotheses 

have termites nested within the Blattaria, we 

have license to turn to extant cockroaches, and in particular 

to Cryptocercus, in our search for a phylogenetic 

framework within which termite eusociality, and thus the 

lineage, evolved. It is a big topic, and one that can be explored 

from several points of view. Here we take a broad 

approach.We first examine how a variety of behaviors key 

to termite sociality and colony integration have their 

roots in behaviors displayed by living cockroach species. 

We then focus on cockroach development, its control, 

and how it can supply the raw material for the extraordinary 

developmental plasticity currently exhibited by the 

Isoptera. We address evolutionary shifts in developmental 

timing (heterochrony), and how these played crucial 

roles in the genesis and evolution of the termite lineage 

from Blattarian ancestors. We then turn to proximate 

causes of termite eusociality, first discussing how a wood 

diet and the symbionts involved in its digestion and assimilation 

provide a framework for the social transition. 

Finally, using young colonies of Cryptocercus as a model 

of the ancestral state, we show how a simple behavioral 

change, the assumption of brood care duties by the oldest 

offspring in the family, can account for all of the initial, 

defining characteristics of eusociality in termites. 

THE BEHAVIORAL CONTINUUM 

Fig. 9.2 Similarity of feeding behavior in a cockroach and a 

mantid. (A) Supella longipalpa standing on four legs while 

grasping a food item with its spined forelegs. (B) Unidentified 

mantid feeding on a caterpillar, Zaire. Both photos courtesy of 

Edward S. Ross. 

Striking ethological similarities in cockroaches and 

termites have been recognized since the early 1900s 

(Wheeler, 1904). These behavioral patterns probably 

arose in the stem group that gave rise to both taxa (Rau, 

1941; Cornwell, 1968) and may therefore serve as points 

of departure when hypothesizing a behavioral profile of 

a termite ancestor. The most frequently cited behaviors 

shared by cockroaches and termites are those that regulate 

response to the physical environment. Both taxa are, 

in general, strongly thigmotactic (Fig. 3.7), adverse to 

light, and associated with warm temperatures and high 

humidity (Wheeler, 1904; Pettit, 1940; Ledoux, 1945). 

Additional shared behaviors include the use of conspecifics 

as food sources (Tables 4.6 and 8.4), the ability 

to transport food (Chapter 4), aggregation behavior, 

elaborate brood care (Chapter 8), hygienic behavior, allogrooming 

(Chapter 5), and antennal cropping, discussed 

below. The remaining behaviors common to Blattaria 

and Isoptera fall into one of two broad domains that 

we address in the following sections: those related to 

communication (vibrational alarm behavior, trail following, 

kin recognition) and those associated with nesting 

and building behavior (burrowing, substrate manipulation, 

behavior during excretion). 

Communication: The Basis 

of Integrated Behavior 

Complex communication is a hallmark of all social insects 

(Wilson, 1971). Most termites and cockroaches, 

however, differ from mantids and the majority of Hymenoptera 

in conducting all day-to-day activities, including 

foraging, in the dark. Both Blattaria and Isoptera 

rely heavily on non-visual mechanisms to orient to resources, 

to guide locomotion, and to communicate. 

Vibrational Communication 

Termites use vibratory signals in several functional contexts. 

Drywood termites, for example, assess the size of 

wood pieces by using the resonant frequency of the substrate 

(Evans et al., 2005). When alarmed, many termite 

species exhibit vertical (head banging) or horizontal 

oscillatory movements that catalyze increased activity 

throughout the colony (Howse, 1965; Stuart, 1969). 

152 COCKROACHES

While cockroaches are known to produce a variety of 

acoustic stimuli in several functional contexts (Roth and 

Hartman, 1967), a recent review of vibrational communication 

included no examples of Blattaria (Virant- 

Doberlet and Cokl, 2004). It is known, however, that Periplaneta 

americana is capable of detecting substrate-borne 

vibration via receptors in the subgenual organ of the tibiae 

(Shaw, 1994b), and that male cockroaches use a variety 

of airborne and substrate-borne vibratory signals 

when courting females, including striking the abdomen 

on the substrate. Tropical cockroaches that perch on 

leaves during their active period may be able to detect 

predators or communicate with conspecifics via the substrate 

(Chapter 6). Adults and nymphs of Cryptocercus 

transmit alarm to family members via oscillatory movements 

nearly identical to those of termites (Cleveland et 

al., 1934; Seelinger and Seelinger, 1983). 

Trail Following 

In termites, trail following mediates recruitment and is a 

basic component of foraging behavior. In several species, 

the source of the trail pheromone is the sternal gland 

(Stuart, 1961, 1969; Peppuy et al., 2001). Cockroaches 

that aggregate are similar to eusocial insects in that there 

is a rhythmical dispersal of groups from, and return to, a 

fixed point in space (e.g., Seelinger, 1984), suggesting that 

cockroaches have navigational powers that allow them to 

either (1) resume a previously established membership in 

a group or (2) find their harborage. It is difficult to separate 

the two, and site constancy and homing ability may 

be a general characteristic of cockroaches regardless of 

their social patterns (Gautier and Deleporte, 1986). Periplaneta 

americana and B. germanica follow paths established 

by conspecifics as well as trails of fecal extracts (Bell 

et al., 1973; Kitamura et al., 1974; Miller and Koehler, 

2000). Brousse-Gaury (1976) suggested that adult P. 

americana use the sternal gland to deposit a chemical trail 

during forays from the harborage. When the antennae of 

P. americana were crossed and glued into place, the cockroaches 

consistently turned in the opposite direction of a 

pheromonal trail in t-mazes, indicating that the mechanism 

employed is a comparison between the two antennae 

(Bell et al., 1973). There are indications of this kind 

of chemo-orientation in other species as well. The myrmecophile 

Attaphila fungicola follows foraging trails of its 

host ant (Moser, 1964), and female cockroaches that have 

recently buried oothecae may disturb the substrate in an 

attempt to obliterate odor trails from detection by cannibals 

(Rau, 1943). 

Kin Recognition 

Kin recognition is well developed in those cockroach 

species in which it has been sought. Juveniles of B. germanica 

are preferentially attracted to the odor of their 

own population or strain (Rivault and Cloarec, 1998). 

Paratemnopteryx couloniana females recognize their sisters 

(Gorton, 1979), first instars of Byrsotria fumigata recognize 

and orient to their own mother (Liechti and Bell, 

1975), and juveniles of Rhyparobia maderae prefer to aggregate 

with siblings over non-siblings, a tendency most 

pronounced in first instars (Evans and Breed, 1984). 

Nymphs of Salganea taiwanensis up to the fifth instar are 

capable of distinguishing their parents from conspecific 

pairs (T. Matsumoto and Y. Obata, pers. comm. to CAN). 

Like termites (reviewed by Vauchot et al., 1998), nonvolatile 

pheromones in the cuticular hydrocarbons can 

and do transfer among individuals via physical contact in 

cockroach aggregations (Roth and Willis, 1952a; Everaerts 

et al., 1997; discussed in Chapter 3). 

Home Improvement: Digging, Burrowing, 

and Building 

Among the social insects, termites are noted for the diversity 

and complexity of their nest architecture. Both 

fecal deposits and exogenous materials (soil, wood) 

transported by the mandibles are used as construction 

material, and the structure is made cohesive with a 

mortar of saliva and fecal fluid. Intricate systems of 

temperature regulation and ventilation are typically incorporated, 

resulting in a protected, climate-controlled 

environment for these vulnerable insects (Noirot and 

Darlington, 2000). Cockroaches exhibit rudimentary forms 

of these complex construction behaviors, providing support 

for the notion that termite construction skills are derivations 

of abilities already present in their blattarian ancestors 

(Rau, 1941, 1943). 

A number of cockroach species tunnel in soil, leaf litter, 

guano, debris, rotten, and sometimes sound, wood 

(Chapters 2 and 3). Cockroaches also possess the morphological 

and behavioral requisites for more subtle 

excavation of substrates, as evidenced in oviparous 

cockroaches during the deposition and concealment of 

oothecae (Fig. 7.2) (McKittrick et al. 1961; McKittrick, 

1964). On particulate substrates such as sand female Blattidae 

use a raking headstroke to dig a hole, but they gnaw 

crevices in more solid substances like wood. Blattellidae 

bite out mouthfuls of material on all substrate types. Legs 

may be used to help dig holes and to move debris away 

from the work site. Euzosteria sordida digs a hole using 

backstrokes of the head, followed by movement of each 

leg in turn to move sand away from the excavation site 

(Mackerras, 1965b). After the hole is the appropriate 

depth, the female has a “molding phase,” during which 

she lines the bottom of the hole with a sticky layer of substrate 

particles mixed with saliva. The ootheca is then de- 


posited in or near the hole, and adjusted into position 

with the mouthparts. A mixture of saliva and finely masticated 

substrate is applied to the surface of the egg case, 

and the remaining gaps are filled with dry material. The 

whole operation can last more than an hour (McKittrick 

et al. 1961; McKittrick, 1964). Females can be quite selective 

in their choice of building material. Rau (1943) noted 

that Blatta orientalis chooses large grains of sand and discards 

the small ones. In P. americana the egg case may be 

plastered with cockroach excrement dissolved in saliva 

(Rau, 1943). It should be noted in this regard that, like 

termites, cockroaches produce a heterogeneous mix of 

excretory products (Nalepa et al., 2001a). These may be 

distinguished in some species by the behavior of the 

excretor, the reaction of conspecifics in the vicinity, and 

the nature of the fecal material. Cockroaches that are domestic 

pests are well known for producing both solid fecal 

pellets and smears attached to the substrate. Both 

Lawson (1965) and Deleporte (1988) describe distinct 

and systematic defecation behaviors in P. americana that 

are reminiscent of termites during nest building. These 

include backing up prior to defecation, then dragging the 

tip of the abdomen on the substrate while depositing a fecal 

droplet. 

Some cockroach species actively modify their living environment. 

Arenivaga apacha dwell in the burrows of 

kangaroo rats, within which they construct small living 

spaces lined with the nest material of their host (Chapter 

3). The soil associated with these spaces is of unusually 

fine texture because the cockroaches work the soil with 

their mouthparts, reducing gravel-sized lumps to fine 

sand and silt-textured soil (Cohen and Cohen, 1976). Eublaberus 

posticus shapes the soft mass of malleable bat 

guano along the base of cave walls into irregular horizontal 

galleries (Fig. 9.3). These are subsequently consolidated 

by calcium carbonate from seepage water (Darlington, 

1970). It is unclear whether the cockroaches 

actively build these structures or whether the hollows are 

epiphenomena, by-products of the insects’ tendency to 

push themselves under edges and into small irregularities 

(Darlington, pers. comm. to CAN). The observation by 

Deleporte (1985) that various developmental stages of P. 

americana dig resting sites in clay walls suggests the former. 

Cockroaches in the Cryptocercidae in many ways exhibit 

nest construction and maintenance behavior comparable 

to that of dampwood termites (Termopsidae). 

When initiating a nest, adult Cryptocercus actively excavate 

galleries; their tunnels are not merely the side effects 

of feeding activities. They eject frass from the nest, plug 

holes and gaps (Fig 9.4A), build pillars and walls to partition 

galleries, and erect barriers when their galleries approach 

those of families adjacent in the log (Nalepa, 1984, 

Fig. 9.3 Shelters fashioned from wet guano along the base of 

cave walls by Eublaberus posticus, Tamana main cave, Trinidad; 

note cockroaches in crevices. The insects may actively construct 

these structures, or they may result from the cockroach 

tendency to wedge into crevices. From Darlington (1970); 

photo and information courtesy of J.P.E.C. Darlington. 

Fig. 9.4 Constructions of Cryptocercus punctulatus. (A) Detail 

of material used to plug holes and seal gaps; here it was sealing 

the interface between a gallery opening and the loose bark that 

covered it. Both fecal pellets (arrow) and small slivers of wood 

are present. (B) Sanitary behavior: fecal paste walling off the 

body of a dead adult (arrow) in a side chamber. An adult male 

was the only live insect present in the gallery system. Photos by 

C. A. Nalepa. 

154 COCKROACHES

unpubl. obs.). Building activity is most common when 

the cockroaches nest in soft, well-rotted logs, and, like 

Zootermopsis and some other termites (Wood, 1976; 

Noirot and Darlington, 2000), excrement and masticated 

wood are the principal construction materials. If logs are 

damp, fecal pellets lose their discrete packaging and become 

a mass of mud-like frass. 

Cryptocercus also exhibits a number of termite-like behaviors 

in maintaining a clean house. In addition to expelling 

frass from galleries, adults keep the nursery area 

(i.e., portion of the gallery with embedded oothecae) 

clear of fungal growth and the fecal mud that commonly 

lines the walls of galleries in the remainder of the nest 

(Nalepa, 1988a). They are known to eat dead nestmates, 

but, like termites (Weesner, 1953; Dhanarajan, 1978), 

Cryptocercus will bury unpalatable corpses in unused 

portions of the gallery (Fig. 9.4B). 

DEVELOPMENTAL FOUNDATIONS 

The influence of hemimetabolous development in the 

evolution of termite societies has long been recognized 

(Kennedy, 1947; Noirot and Pasteels, 1987). Unlike the 

holometabolous Hymenoptera, termite juveniles do not 

have to mature before they are capable of work. Hemimetabolous 

insects also tend to grow less between molts 

and molt more often over the course of development 

(Cole, 1980). This is due, at least in part, to differences in 

nutritional efficiency between the two groups. The conversion 

of digested food to body mass can be 50% greater 

in holometabolous insects, possibly because they do not 

need to produce and maintain a large mass of cuticle during 

the juvenile stage (Bernays, 1986). 

Termite Development 

In the Isoptera, day-to-day colony labor is the responsibility 

of juveniles—termites whose development has 

been truncated, either temporarily or permanently, relative 

to reproductives. Even terminal nonsexual stages (i.e., 

soldiers, and workers in some species) are considered immature, 

because they retain their prothoracic glands, 

which degenerate in all sexual forms. The only imagoes 

in the termitary are the king and queen (Noirot, 1985; 

Noirot and Pasteels, 1987; Noirot and Bordereau, 1989). 

The degree, permanence, timing, and reversal of developmental 

arrest, together with the organs subject to these 

changes, determine which developmental pathway is 

taken during the ontogeny of particular groups (Noirot 

and Pasteels, 1987; Roisin, 1990, 2000). This developmental 

flexibility is mediated by a combination of progressive, 

stationary, and reversionary molts, and is distinctive. 

Dedifferentiation of brachypterous nymphs in 

termites is the only known instance of a natural reversal 

of metamorphosis in insects (Nijhout and Wheeler, 

1982). The extraordinary complexity and sophistication 

characteristic of termite development is nonetheless 

rooted in mechanisms of postembryonic development 

observed in non-eusocial insects (Bordereau, 1985). The 

developmental characteristics of cockroach ancestors, 

then, were the phylogenetic foundation on which termite 

polyphenisms were built. 

Cockroach Development 

Within a cockroach species, both the number and duration 

of instars that precede the metamorphic molt are 

variable, a trait unusual among hexapods (Heming, 

2003). In P. americana, for example, the length of 

nymphal period can vary from 134 to 1031 days (Roth, 

1981a)—nearly an order of magnitude. The number of 

molts in cockroaches varies from 5 or 6 to 12 or 13, and 

may or may not vary between the sexes. Within a species, 

variation in cockroach development occurs primarily in 

response to environmental conditions: low temperature, 

minor injuries, water or food deficits, or poor food quality 

(Tanaka, 1981; Mullins and Cochran, 1987). Even in 

laboratory cultures in which extrinsic influences have 

been minimized or controlled, however, the instar of 

metamorphosis remains variable, even in nymphs from 

the same ootheca (Kunkel, 1979; Woodhead and Paulson, 

1983). There can be a lag of up to 9 mon between the appearance 

of the first and last adult among nymphs from 

the same sibling cohort of Periplaneta australasiae (Pope, 

1953), and “runts”—nymphs stalled in the third or 

fourth instar when all others in the cohort have matured—have 

been noted in P. americana (Wharton et al., 

1968). Kunkel (1979) describes the instar of metamorphosis 

in cockroaches as a polygenic trait with a great 

deal of environmental input involved in its expression. 

Significantly, there are records of both stationary and 

saltatory molts in cockroaches (Gier, 1947; Rugg and 

Rose, 1990). If the ancestor of the termites was like extant 

cockroaches, then it, too, possessed a tremendous 

amount of developmental plasticity prior to evolving eusociality. 

Control of Development 

An examination of conditions known to modify cockroach 

development may provide insight into the origins 

of termite polyphenism, the proximate causes of which 

are still little understood (Bordereau, 1985; Roisin, 2000). 

Here we focus on three extrinsic factors that may have 

influenced development as the termite lineage evolved: 

minor injuries, nourishment, and group effects. Each of 


these has a social component, in that each can be based 

on interactions with conspecifics rather than the external 

environment. 

Injury and Development 

There is a large body of literature indicating that minor 

wounds in cockroach juveniles delay development. Injuries 

to legs, cerci, and antennae result in an increased 

number of instars, in the prolonged duration of an instar, 

or both (Zabinski, 1936; Stock and O’Farrell, 1954; Willis 

et al., 1958; Tanaka et al., 1987). The developmental delay 

may be attributed to the allocation of limited resources, 

because energy and nutrients directed into wound repair 

and somatic regeneration are unavailable for progressive 

development (Kirkwood, 1981). This relationship between 

injury and development may be relevant to termites 

in two contexts. First, in a variety of lower termites, 

mutilation of the wing pads and occasionally other body 

parts is common (e.g., Myles, 1986). These injuries are 

hypothesized to result from the bites of nest mates, and 

they determine which individuals fly from the nest and 

which remain to contribute to colony labor. Injured individuals 

do not proceed to the alate stage, but instead undergo 

regressive or stationary molts (Roisin, 1994). The 

aggressive interactions that result in these injuries may be 

the expression of sibling manipulation if larvae, nymphs, 

or other colony members are doing the biting (Zimmerman, 

1983; Myles, 1986), or they could indicate fighting 

among nymphs that are competing for alate status 

(Roisin, 1994). 

A second, peculiar, termite behavior also may be linked 

to the physiological consequences of injury. After a 

dealate termite pair becomes established in its new nest, 

the male and female typically chew off several terminal 

segments of their own antennae, and/or those of their 

partner (e.g., Archotermopsis—Imms, 1919; Cubitermes 

—Williams, 1959; Porotermes—Mensa-Bonsu, 1976; 

Zootermopsis—Heath, 1903). This behavior is also 

recorded in several cockroach taxa. Nymphs of B. germanica 

self-prune their antennae (autotilly)—the ends 

are nipped off just prior to molting (Campbell and Ross, 

1979). Although first and second instars of Cryptocercus 

punctulatus almost always have intact antennae, cropped 

antennae can be found in third instars and are common 

in fourth instars (Nalepa, 1990). Nymphs and adults of 

the myrmecophiles Att. fungicola and Att. bergi usually 

have mutilated antennae (Bolívar, 1901; Brossut, 1976), 

but Wheeler (1900) was of the opinion that it was the host 

ants that trimmed them for their guests. He likened it to 

the human habit of cropping the ears and tails of dogs. 

The developmental and/or behavioral consequences of 

antennal cropping are unknown for both termites and 

cockroaches. 

Nutrition and Development 

Cockroach development is closely attuned to nutritional 

status (Gordon, 1959; Mullins and Cochran, 1987). Poor 

food quality or deficient quantity results in a prolongation 

of juvenile development via additional molts and/or 

prolonged intermolts (Hafez and Afifi, 1956; Kunkel, 

1966; Hintze-Podufal and Nierling, 1986; Cooper and 

Schal, 1992). Diets relatively high in protein produce the 

most rapid growth (Melampy and Maynard, 1937), and 

on diets lacking protein, nymphs survive for up to 8 mon, 

but eventually die without growing (Zabinski, 1929). The 

effect of nutrition on development is most apparent in 

early instars, corresponding to what is normally their period 

of maximum growth (Woodruff, 1938; Seamans and 

Woodruff, 1939). A nutrient deficiency in a juvenile cockroach 

results in a growth stasis, in which a semi-starved 

nymph “idles”until a more adequate diet is available. This 

plasticity in response to the nutritional environment is 

suggestive of the arrested development exhibited by 

workers (pseudergates) in lower termite colonies, and is 

hypothesized to be one of the key physiological responses 

underpinning the shift from subsocial to eusocial status 

in the termite lineage (Nalepa, 1994, discussed below). 

Reproductive development is also closely regulated by 

the availability of food in cockroaches. Females stop or 

slow down reproduction until nutrients, particularly the 

amount and quality of ingested protein, is adequate 

(Weaver and Pratt, 1981; Durbin and Cochran, 1985; 

Pipa, 1985; Mullins and Cochran, 1987; Hamilton and 

Schal, 1988). In P. americana the initial response to lack 

of food is simply the slowing down of oocyte growth, but 

if starvation becomes chronic the corpora allata are 

turned off and reproduction effectively ceases. When 

food once again becomes available the endocrine system 

is rapidly reactivated and normal reproductive activity 

follows within a short time (Bell and Bohm, 1975). 

Kunkel (1966, 1975) used feeding as an extrinsically controllable 

cue for synchronizing both the molting of 

nymphs and the oviposition of females in B. germanica 

and P. americana. There is substantial evidence, then, that 

domestic cockroaches tightly modulate “high demand” 

metabolic processes such as reproduction and development 

in response to changes in food intake, and that both 

physiological processes can be controlled in individuals 

by manipulating their food source. 

Group Effects and Development 

Group effects (discussed in Chapter 8) can have a profound 

effect on the developmental trajectory of juvenile 

cockroaches and are known from at least three families of 

Blattaria (Table 8.3). Nymphs deprived of social contact 

typically have longer developmental periods, resulting 

156 COCKROACHES

from both decreased weight gain per stadium and increased 

stadium length (Griffiths and Tauber, 1942b; 

Willis et al., 1958; Wharton et al., 1968; Izutsu et al., 1970; 

Woodhead and Paulson, 1983). In P. americana, nymphs 

isolated at day 0 are one-half to one-third the size of 

grouped nymphs after 40 days (Wharton et al., 1968). The 

effect is cumulative, with no critical period. It occurs at 

any stage of development and is reversible at any stage 

(Wharton et al., 1967; Izutsu et al., 1970). Respiration of 

isolates may increase, and new proteins, expressed as 

electrophoretic bands, may appear in the hemolymph 

(Brossut, 1975; pers. comm. to CAN). The physiological 

consequences seem to be caused by a lack of physical contact 

(Pettit, 1940; Izutsu et al., 1970) and the presence of 

even one other individual can ameliorate the effects 

(Izutsu et al., 1970; Woodhead and Paulson, 1983). The 

means by which tactile stimuli orchestrate the physiological 

changes characteristic of the group effect in cockroaches 

is unknown. In termites, as in cockroaches, the 

physical proximity of conspecifics significantly increases 

the longevity and vigor of individuals, with just one nestmate 

as sufficient stimulus. This “reciprocal sensory intimacy” 

is thought to play a key, if unspecified, role in caste 

determination (Grassé, 1946; Grassé and Noirot, 1960). 

Heterochrony: Evolutionary Shifts 

in Development 

Termites are essentially the Peter Pans of the insect 

world—many individuals never grow up. Most colony 

members are juveniles whose progressive development 

has been suspended. Even mature adult termites exhibit 

numerous juvenile traits when compared to adult cockroaches, 

the phylogenetically appropriate reference group 

(Nalepa and Bandi, 2000). Termites therefore may be described 

as paedomorphic, a term denoting descendent 

species that resemble earlier ontogenetic stages of ancestral 

species (Reilly, 1994). The physical resemblance of 

termites and young cockroaches is indisputable, and is 

most obvious in the bodily proportions, the thin cuticle, 

and a short pronotum that leaves the head exposed. 

Cleveland et al. (1934) and Huber (1976) both noted the 

resemblance of early instars of Cryptocercus to larger termite 

species, with the major difference being the more 

rapid movement and longer antennae of Cryptocercus 

(Fig. 9.5). One advantage that termites gain by remaining 

suspended in this thin-skinned morphological state is the 

avoidance of a heavy nitrogenous (Table 4.5) investment 

in cuticle typical of older developmental stages of their 

cockroach relatives. 

Cockroaches that are paedomorphic display a variety 

of termite-like characters such as thinning of the cuticle, 

eye reduction, and decrease in the size of the pronotal 

Fig. 9.5 First instar of Cryptocercus punctulatus. Photo by C.A. 

Nalepa. 

shield (e.g., Nocticola australiensis—Roth, 1988). These 

cockroaches are often wingless, but when wings are retained 

they can resemble those of termite alates. In Nocticola 

babindaensis and the genus Alluaudellina ( Alluaudella), 

the forewings and hindwings are nearly the same 

length, they considerably exceed the tip of the abdomen, 

both sets are membranous, and they have a reduced venation 

and anal lobe (Shelford, 1910a; Roth, 1988). 

The expression of altered developmental timing in termites 

is not limited to morphological characters. It includes 

aspects of both behavior and physiology that are 

more characteristic of the juvenile rather than the adult 

stages of their non-eusocial relatives. Just as maturation 

of the body became truncated during paedomorphic evolution 

in the termite lineage, so did many features of behavioral 

and physiological development. Elsewhere in 

this chapter we noted several behaviors that are common 

to termites and cockroach taxa, including burrowing, 

building, substrate manipulation, trail following, and vibrational 

alarm behavior. There are additional behaviors 

crucial to termite social cohesion shared only with the 

early developmental stages of cockroaches (Nalepa and 

Bandi, 2000). In most cockroach species, young nymphs 

have the strongest grouping tendencies, and in some, 

early instars are the only stages that aggregate (Chapter 

8). Early cockroach instars often display the most pronounced 

kin recognition (Evans and Breed, 1984), the 

most intense cannibalism (Wharton et al., 1967; Roth, 

1981a), and the most frequent coprophagy (Nalepa and 

Bandi, 2000).Young Periplaneta nymphs affix fecal pellets 

to the substrate more often than do older stages (Deleporte, 

1988). Antennal cropping is displayed in nymphs 

of two cockroach species, and it is only young developmental 

stages of Cryptocercus that allogroom (Seelinger 

and Seelinger, 1983). All of these behaviors are standard 

elements of the termite behavioral repertoire. 


Many behaviors shared by termites and young cockroaches 

relate to food intake. Termites also resemble 

cockroach juveniles in aspects of digestive physiology and 

dietary requirements (Nalepa and Bandi, 2000). More so 

than older stages, early instars of cockroaches rely on 

conspecific food and ingested microbial protein to fuel 

growth, and are dependent on the metabolic contributions 

of microbial symbionts in both the gut and fat body 

for normal development. As termites evolved, they elaborated 

on this food-sharing, microbe-dependent mode 

instead of shifting to a more adult nutritional physiology 

during ontogenetic growth. 

Caste control in termites also may be rooted in the developmental 

physiology of young cockroaches (Nalepa 

and Bandi, 2000). It is the early cockroach instars that are 

most susceptible to developmental perturbations related 

to nutrition, injury, and group effects (Woodruff, 1938; 

Seamans and Woodruff, 1939; Holbrook and Schal, 

1998). Moreover, these stimuli are extrinsically controllable 

and may allow for manipulation of individual development 

by fellow colony members (Nalepa and Bandi, 

2000). 

In sum, a large number of the juvenile characters of 

their cockroach ancestors were co-opted by termites in 

the course of their evolution, and these were integral in 

the cascade of adaptations and co-adaptations that resulted 

in the highly derived, eusocial taxon it is today. 

Heterochrony is known to provide a basis for rapid divergence 

and speciation, because integrated character sets 

are typically under a system of hierarchical control 

(Gould, 1977; Futuyma, 1986). Simple changes in regulatory 

genes, then, can result in rapid, drastic phenotypic 

changes (Futuyma, 1986; Stanley, 1998). 

WOOD DIET, TROPHALLAXIS, 

AND SYMBIONTS 

That the character and direction of Isopteran 

evolution as a whole has been in the main determined 

by their peculiar food is obvious. 

—Wheeler, The Social Insects 

There are distinct advantages to living within your 

food source. Logs offer mechanical protection and refuge 

from a number of predators and parasites, with an interior 

temperature and humidity generally more moderate 

than that of the external environment. Abundant if lowquality 

food is always close at hand. One disadvantage is 

that when on this fixed diet, a wood-feeding dictyopteran 

would forfeit the opportunity to move within the habitat 

seeking specific nutrients and nitrogenous bonanzas 

(e.g., bird droppings) as its developmental and reproductive 

needs change. Reliance on slowly accumulated reserves 

and the use of food originating from conspecific 

sources, then, would become considerably more important, 

particularly in those stages with a high nitrogen 

demand—reproducing females and young nymphs (Nalepa, 

1994). 

Termites inherited from cockroaches a suite of interindividual 

behaviors that allow for nitrogen conservation 

at the colony level and provide a means of circulating 

it among individuals within the social group (Table 

4.6). These include cannibalism, necrophagy, feeding on 

exuviae, and coprophagy. Two behaviors of particular 

note are allogrooming and trophallaxis, first, because 

they supply the organizational glue that keeps termite 

colonies cohesive and functional, and second, because 

among cockroaches these behaviors are only known from 

wood-feeding species. Allogrooming has been noted in 

Panesthia (M. Slaytor, pers. comm. to CAN) and Cryptocercus, 

and in the latter it occurs exactly as described in 

termites by Howse (1968). The groomer grazes on the 

body of a conspecific, and the insect being groomed responds 

by rotating its body or appendages into more accessible 

positions (Fig. 5.5B).As with termites, the nymph 

being tended may enter a trance-like state and afterward 

remain immobile for a short period of time before resuming 

activity (Nalepa and Bandi, 2000). 

Trophallaxis is the circulatory system of a termite 

colony. It is the chief mechanism of disseminating water, 

nutrients, hormones, dead and live symbionts, and the 

metabolic products and by-products of the host and all 

its gut symbionts. Stomodeal trophallaxis (by mouth) occurs 

in all termite families, and proctodeal trophallaxis 

(by anus) occurs in all but the derived family Termitidae 

(McMahan, 1969; Breznak, 1975, 1982). Both types of 

trophallaxis occur in wood-feeding cockroaches, and in 

these taxa the behaviors occur in the context of parental 

care. Salganea taiwanensis feeds its young on oral secretions 

(T. Matsumoto, pers. comm. to CAN; Fig. 8.3B), and 

Cryptocercus adults feed young nymphs on hindgut fluids 

(Seelinger and Seelinger, 1983; Nalepa, 1984; Park et al., 

2002). 

Hindgut Protozoa 

Digestion in Cryptocercus is comparable to that of lower 

termites in all respects. The hindgut is a fermentation 

chamber filled to capacity with a community of interacting 

symbionts, including flagellates, spirochetes, and bacteria 

that are free in the digestive tract, attached to the gut 

wall, and symbiotic with resident protozoans. Included 

are uricolytic bacteria, cellulolytic bacteria, methano- 

158 COCKROACHES

Fig. 9.6 Scanning electron micrographs of flagellates from the hindgut of Cryptocercus punctulatus. 

(A) The hypermastigote Trichonympha sp., scale bar 25 m. (B) The oxymonad Saccinobaculus 

sp., scale bar 5 m. Images courtesy of Kevin J. Carpenter and Patrick J. Keeling. 

gens, and those capable of nitrogen fixation, as well as 

bacteria that participate in the biosynthesis of volatile 

fatty acids (Breznak et al., 1974; Breznak, 1982; Noirot, 

1995). 

The common possession of oxymonad and hypermastigid 

hindgut flagellates in Cryptocercus and lower 

termites (Fig. 9.6) is often a focal point in discussions of 

the evolutionary origins of termites. These protozoans 

are unusually large, making them good subjects for a variety 

of experimental investigations; some in the gut of 

Cryptocercus are 0.3 mm in length and visible to the unaided 

eye (Cleveland et al., 1934). They are unusually intricate, 

with singular morphological structures and a 

complex of bacterial symbionts of their own (e.g., Noda 

et al., 2006). They are unique; most are found nowhere in 

nature but the hindguts of these two groups (Honigberg, 

1970). Finally, and of most interest for termite evolutionary 

biology, most are cellulolytic and interdependent with 

their hosts. For many years these flagellates were thought 

to be not only the sole mechanism by which dictyopteran 

wood feeders digested cellulose, but also the proximate 

cause of termite eusociality. Currently, however, neither 

of these hypotheses is fully supported, despite misconceptions 

that still abound in the literature. 

Dependence on Flagellates for Cellulase? 

All termites and all cockroaches examined to date produce 

their own cellulases, which are distinct from and 

unrelated to those produced by the hindgut flagellates 

(Watanabe et al., 1998; Lo et al., 2000; Slaytor, 2000; 

Tokuda et al., 2004). The common possession of a certain 

family of cellulase genes (GHF9) in termites, cockroaches, 

and crayfish suggest that these enzymes were established 

in the Dictyopteran lineage long before flagellates 

took up permanent residence in the hindguts of an 

ancestor of the termite-Cryptocercus clade (references in 

Lo et al., 2003b). At present, Cryptocercus and lower termites 

are considered to have a dual composting system 

(Nakashima et al., 2002; Ohkuma, 2003); cellulose is degraded 

by the combined enzymes of the host and the 

hindgut flagellates. Nonetheless, these hosts are dependent 

on the staggeringly complex communities of mutually 

interdependent co-evolved organisms from the Archaea, 

Eubacteria, and Eucarya in their digestive systems. 

The interactions of the microbes with each other and 

with their hosts are still poorly understood; however, exciting 

inroads are being made by the laboratories actively 

studying them, and the field is advancing quickly (e.g., 

Tokuda et al., 2004, 2005; Inoue et al., 2005; Watanabe et 

al., 2006). Products of cellulose degradation by gut protozoans 

may indirectly benefit the insect host by providing 

energy for anaerobic respiration and nitrogen fixation 

in gut bacteria (Bignell, 2000a; Slaytor, 2000). A comparison 

of gene expression profiles among castes of the termite 

Reticulitermes flavipes suggests that cellulases produced 

by the symbionts may be particularly important in 


incipient colonies (Scharf et al., 2005). This supports the 

idea that gut microbes may supply a metabolic boost at 

crucial points in host life history. 

Flagellates Cause Eusociality? 

Hindgut protozoans were crucial in the evolution of eusociality 

in their termite hosts, but not for the reasons 

usually cited. In termites, the hindgut flagellates die just 

prior to host ecdysis. A newly molted individual must 

reestablish its symbiosis by proctodeal trophallaxis from 

a donor nestmate, making group living mandatory. In the 

classic literature, this codependence of colony members 

was thought to be the main precondition for the evolution 

of eusociality in termites; the idea can be traced to 

the work of L.R. Cleveland (1934). While loss of flagellates 

at molt may enforce proximity, it provides no 

explanation for the defining characteristics of termite eusociality, 

namely, brood care, overlapping worker generations, 

and non-reproductive castes (Starr, 1979; Andersson, 

1984). Moreover, the bulk of evidence suggests that 

protozoan loss at molt in termites did not precede eusociality. 

It is a secondary condition derived from eusociality 

of the hosts, and is associated with the physiology of 

developmental arrest and caste control (Nalepa, 1994). 

Hindgut protozoans were crucial in the genesis of the 

termite lineage, because an obligate symbiotic relationship 

with them demands a reliable means of transmission 

between generations. The life history characteristics of a 

termite ancestor, as exemplified by Cryptocercus, combined 

with the physiology of encystment of these particular 

protozoans, mandate that this transmission could 

only occur via proctodeal trophallaxis (Nalepa, 1994). In 

an ancestor common to Cryptocercus and termites, flagellate 

cysts were presumably passed to hatchlings by intraspecific 

coprophagy in aggregations (Nalepa et al., 

2001a). The physiology of encystment in these protists, 

however, does not allow for their transmission by adults. 

Their encystment is triggered by the molting cycle of the 

host; consequently they are passed in the feces only during 

the developmental stages of nymphs. Cysts are never 

found in the feces of adults or intermolts (Cleveland et al., 

1934; Cleveland and Nutting, 1955; Cleveland et al., 

1960). Cryptocercus is subsocial and semelparous. Most 

adults spend their entire lives nurturing one set of offspring. 

Consequently, older nymphs are not present in 

galleries when adults reproduce (Seelinger and Seelinger, 

1983; Nalepa, 1984; Park et al., 2002). Coprophagy as a 

mechanism of intergenerational transmission is thus 

ruled out; adults do not excrete cysts, and older nymphs 

are absent from the social group. Cysts in the feces of 

molting Cryptocercus nymphs, as well as vestiges of the 

sexual/encystment process in termites (Grassé and Noirot, 

1945; Cleveland, 1965; Messer and Lee, 1989), are a 

legacy of their distant gregarious past. In the ancestor 

Cryptocercus shared with termites, an obligate relationship 

with gut symbionts, intergenerational transmission 

via proctodeal trophallaxis, and subsociality were thus a 

co-evolved character set (Nalepa, 1991; Nalepa et al., 

2001a). Proctodeal trophallaxis in young families of a 

Cryptocercus-like ancestor assured not only passage of 

cellulolytic flagellates between generations, but also passage 

of the entire complex of microorganisms present in 

the hindgut fluids. Trophallaxis thus conserved relationships 

between microbial taxa within consortia, allowing 

them to develop interdependent relationships by eliminating 

redundant pathways. The metabolic efficiency 

of these consortia consequently increased, shifting the 

cost-benefit ratio in favor of increased host reliance. The 

growing dependence of the host on gut microbes, in turn, 

reinforced selection for assured passage between generations 

via subsociality and trophallactic behavior. The 

switch from horizontal to vertical intergenerational 

transmission of gut fauna was thus one of the key influences 

in the transition from gregarious to subsocial behavior 

in the common ancestor of Cryptocercus and termites. 

It also set up one of the pivotal conditions allowing 

for the transition to eusociality by establishing the behavioral 

basis of trophallactic exchanges (Nalepa et al., 

2001a). 

The hypothesis that the loss of protozoan symbionts at 

molt was influential during the initial transition to eusociality, 

then, is not supported. The interdependence that 

the condition enforces on hosts nonetheless played a key 

role after the initial transition from subsociality to eusociality 

(detailed below). Subsequent hormonal changes 

related to developmental stasis and caste evolution, and 

the associated loss of protozoans at molt resulted in a 

“point of no return” (Hölldobbler and Wilson, 2005), 

when individuals became incapable of a solitary existence. 

DOUBLE SYMBIOSIS: THE ROLE 

OF BACTEROIDS 

A hindgut filled to capacity with a huge complex of interacting 

microbiota was not the only symbiotic association 

influential in the evolution of termite eusociality. 

Grassé and Noirot (1959) noted nearly a half-century ago 

that the two taxa bracketing the transition from cockroaches 

to termites share a unique double symbiosis: an 

association with cellulolytic flagellates in the hindgut, and 

endosymbiotic bacteria housed in the visceral fat body. 

Cryptocercus is the only cockroach that has the former 

symbiosis, which it shares with all lower termites, and 

160 COCKROACHES

Mastotermes (Fig. 9.7) is the only isopteran with the latter, 

which it shares with all examined Blattaria (Bandi et 

al., 1995; Lo et al., 2003a). Mastotermes has additional 

characters that ally the taxon with cockroaches, including 

a well-developed anal lobe in the hindwing and the packaging 

of eggs in an ootheca (Watson and Gay, 1991; 

Nalepa and Lenz, 2000; Deitz et al., 2003). 

The bacteroid-uric acid circulation system was in place 

when termites evolved eusociality (Fig. 9.1), possibly allowing 

for the mobilization of urate-derived nitrogen 

from the fat body and its transfer among conspecifics via 

coprophagy and trophallaxis (Chapter 5). The endosymbiosis 

was subsequently lost in other termite lineages 

when these diverged from the Mastotermitidae (Bandi 

and Sacchi, 2000). Other termites sequester uric acid in 

the fat body, but without bacteroids, individuals lack the 

ability to mobilize it from storage. Stored reserves can 

only be used by colony members via cannibalism or 

necrophagy. Once ingested, the uric acid is broken down 

by uricolytic bacteria in the hindgut (Potrikus and Breznak, 

1981; Slaytor and Chappell, 1994). Bacteroids were 

likely lost in most termites because two aspects of eusocial 

behavior made fat body endosymbionts redundant. 

The recycling of dead, moribund, and sometimes living 

nestmates, combined with the constant flow of hindgut 

fluids among nestmates via trophallaxis, allowed uricolytic 

gut bacteria to be a more cost-efficient option 

(Bandi and Sacchi, 2000). It is of note, then, that after eusociality 

evolved, the storage and circulation of uric acid 

and its breakdown products changed from one that occurs 

primarily at the level of individual physiology to one 

that occurs at the colony level. It is also of interest that 

proctodeal trophallaxis, a behavior linked to the presence 

of the hindgut symbionts, may have been influential in 

the loss of the fat body endosymbionts. 

EVOLUTION OF EUSOCIALITY 1: 

BASELINE 

Fig. 9.7 Male and female dealate primary reproductives of 

Mastotermes darwiniensis. Photo by Kate Smith, CSIRO Division 

of Entomology. 

A detailed examination of the biology of colony initiation 

in Cryptocercus lends itself to a logical, stepping-stone 

conceptual model of the evolution of the earliest stages of 

termite eusociality, with a clear directionality in the sequence 

of events. Female C. punctulatus lay a clutch of 

from one to four oothecae. Unlike other oviparous cockroaches 

(Fig. 7.1), nymphs do not hatch from the ootheca 

simultaneously. The majority of egg cases require 2–3 

days for all neonates to exit (Nalepa 1988a). Laboratory 

studies further suggest that there is a lag of from 2–6 days 

between deposition of successive oothecae (Nalepa, 

1988a, unpubl. data). Consequently, there can be an age 

differential of 2 or more weeks between the first and last 

hatched nymphs in large broods. These age differentials 

are corroborated by field studies. Families collected during 

autumn of their reproductive year can include second, 

third, and fourth instars (Nalepa, 1990), at which 

point development is suspended prior to the onset of 

their first winter. 

Nymphs in these families hatch without the gut symbionts 

required to thrive on a wood diet; consequently, 

they rely on trophallactic food and fecal pellets (Fig. 5.4) 

from adults for nutrients. Parents apparently provide all 

of the dietary requirements of first-instar nymphs, and 

some degree of trophallactic feeding of offspring occurs 

until their hindgut symbioses are fully established. Individual 

nymphs probably have high nutritional requirements, 

since they gain considerable weight and go 

through a relatively quick series of molts after hatch. The 

young are potentially independent at the third or fourth 

instar (Nalepa, 1990, Table 2), but the family structure is 

generally maintained until parental death. Adults do not 

reproduce again. Because of their extraordinarily long developmental 

times (up to 8 yr, hatch to hatch, depending 

on the species—Chapter 3), adult Cryptocercus rarely, if 

ever, overlap with their adult offspring (CAN, unpubl.). 

In addition to providing food and microbes, parental care 

includes gallery excavation, defense of the family, and 

sanitation of the nest (Cleveland et al., 1934; Seelinger 

and Seelinger, 1983; Nalepa, 1984, 1990; Park et al., 2002). 

This degree of parental care exacts a cost. If eggs are removed 

from Cryptocercus pairs, 52% are able to reproduce 

during the following reproductive period. If parents 


Fig. 9.8 Trophic shift model for transition from subsociality to 

initial stages of eusociality in a termite ancestor. (A) Baseline 

conditions. A series of egg cases are laid over a short period of 

time, resulting in age differentials within the brood. Adults feed 

all offspring; cost of parental care results in reproductive arrest. 

Juveniles develop slowly but progressively toward adulthood. 

(B) Transition to eusociality. Fourth instars begin feeding 

younger siblings; cost of alloparental care results in developmental 

arrest of juvenile caregivers. Female resumes oviposition. 

After Nalepa (1988b, 1994). 

are allowed to take care of neonates for 3 mon prior to 

brood removal, however, only 12% oviposit the following 

summer. This suggests that parental care may deplete reserves 

that were accumulated over the course of their extended 

developmental period and are not easily replaced. 

Under the constraint of a wood diet, their apparent 

semelparity in the field can be attributed to the need for, 

and cost of, long-term parental care of the young (Nalepa, 

1988b). The life history of a subsocial termite ancestor 

similar to that of Cryptocercus is depicted in Fig. 9.8A. 

EVOLUTION OF EUSOCIALITY 2: 

TRANSITION 

It is reasonable to assume that a termite ancestor packaged 

its eggs in oothecae, since the basal termite Mastotermes 

does so (Nalepa and Lenz, 2000). If the timing of 

oviposition in this ancestor was similar to that of Cryptocercus—a 

reproductive burst, with several oothecae laid 

within a relatively short time frame—nymphs in the family 

also exhibited age differentials. It is likely that repro- 

162 COCKROACHES

duction was suspended as adults fed and otherwise cared 

for their dependent neonates, as reproductive stasis occurs 

in extant young termite families when adults are nurturing 

their first set of offspring (reviewed by Nalepa, 

1994). This suggests that, as in Cryptocercus, parental care 

during colony initiation in the termite ancestor was 

costly. 

The crucial step, and one that occurs during the ontogeny 

of extant termite colonies, is that older nymphs assume 

responsibility for feeding and maintaining younger 

siblings, relieving their parents of the cost of brood care 

and allowing them to invest in additional offspring (Fig. 

9.8B). All defining components of eusociality (Michener, 

1969; Wilson, 1971) follow. First, relieved of her provisioning 

duties, the female can redirect her reserves into 

oogenesis, and the result is a second cohort that overlaps 

with offspring produced during the first reproductive 

burst. Second, the assumption of responsibility for 

younger siblings by the oldest offspring in the family constitutes 

brood care. Third, by trophallactically feeding 

younger siblings, fourth instars are depleting reserves that 

could have been channeled into their own development, 

thus delaying their own maturation (Nalepa, 1988b, 

1994). A single behavioral change, the switch from parental 

to alloparental care, thus represents the pathway for 

making a seamless transition between adaptive points, accounting 

with great parsimony for the defining components 

of the early stages of termite eusociality (Nalepa 

1988b, 1994). A key life history characteristic in a Cryptocercus-like 

termite ancestor would be the extraordinarily 

extended developmental period the first workers face, 

even prior to assuming brood care duties. Tacking an addition 

developmental delay onto the half dozen or so 

years these nymphs already require to reach reproductive 

maturity may be a pittance when balanced against the additional 

eggs their already reproductively competent 

mother may be able to produce as a result of their alloparental 

behavior. A preliminary mathematical model indicates 

that when a key resource like nitrogen is scarce, the 

costs of delayed reproduction in these first workers are 

outweighed by the benefits accrued by their labor in the 

colony (Higashi et al., 2000). 4 A cockroach-like developmental 

plasticity supplied the physiological underpinnings 

for the social shift, as high-demand metabolic 

processes such as reproduction and development are 

tightly modulated in response to nutritional status in 

Blattaria. It is of particular interest, then, that in extant 

termites (Reticulitermes) two hexamerin genes may signal 

nutritional status and participate in the regulation of 

caste polyphenism (Zhou et al., 2006). 

4. Masahiko Higashi was tragically killed in a boating accident in 

March 2000 (Bignell, 2000b) and never completed the study. 

HETEROCHRONY REVISITED 

The recognition that heterochronic processes play a fundamental 

role in social adaptations is increasingly recognized 

in birds and mammals (see references in Gariépy et 

al., 2001; Lawton and Lawton, 1986) but to date changes 

in developmental timing have not received the attention 

they deserve in studies of social insect evolution. Heterochrony 

is pervasive in termite evolution, and most aspects 

of isopteran biology can be examined within that 

framework (Nalepa and Bandi, 2000). The evolution of 

the initial stages of termite eusociality from subsocial ancestors 

described above is predicated on a behavioral heterochrony, 

an alteration in the timing of the expression of 

parental care (Nalepa, 1988b, 1994). Recently, behavioral 

heterochrony has been recognized as a key mechanism in 

hymenopteran social evolution as well (Linksvayer and 

Wade, 2005). Behavioral heterochronies often precede 

physiological changes, with the latter playing a subsequent 

supportive role (e.g., Gariépy et al., 2001); behavior 

changes first, developmental consequences follow. 

Development in the first termite workers was suspended 

as a result of the initial behavioral heterochrony in an ancestor, 

and selection was then free to shape a suite of interrelated 

juvenile characters, including allogrooming, 

kin recognition, coprophagy, and aggregation behavior. It 

has been noted that paedomorphic taxa frequently develop 

heightened social complexity, because the reduced 

aggression associated with juvenile appearance and demeanor 

enhances social interactions (e.g., Lawton and 

Lawton, 1986). After alloparental care became established 

in an ancestor, termite evolution escalated as the social 

environment, rather than the external environment, became 

the primary source of stimuli in shaping developmental 

trajectories (Nalepa and Bandi, 2000, Fig. 4). 

Major events were the rise of the soldier caste, the polyphyletic 

onset of an obligately sterile worker caste excluded 

from the imaginal pathway (Roisin, 1994, 2000), 

and the loss of gut flagellates at molt, making group living 

mandatory. The evolution of permanently sterile 

castes is outside the scope of this chapter. We do, however, 

note two conditions among extant young cockroaches 

that provide substructure for the genesis of polyphenism 

and division of labor. First, the potential for caste evolution 

would be stronger in an ancestor with a juvenile 

physiology, because young cockroaches are subject to the 

most powerful group effects. Social conditions during the 

early instars of Diploptera punctata, for example, can irreversibly 

fix future developmental trajectories (Holbrook 

and Schal, 1998). Second, evidence is increasing 

that the process of forming aggregations in cockroaches 

is a self-organized behavior (Deneubourg et al., 2002; 

Garnier et al., 2005; Jeanson et al., 2005). In eusocial in- 


sects, self-organization has been shaped by natural selection 

to produce task specialization, and plays a role in 

building behavior, decision making, synchronization of 

activities, and trail formation (Page and Mitchell, 1998; 

Camazine et al., 2001). 

THE GROUND PLAN 

Nature has set a very high bar for the attainment of eusociality, 

and only extraordinary environmental challenges 

and extraordinary circumstances in prior history can allow 

an organism to scale it (Hölldobbler and Wilson, 

2005). In the termite ancestor, a nitrogen-deficient, physically 

difficult food source was undoubtedly the relevant 

environmental challenge, and costly brood care was an essential 

precedent. Nonetheless, the evolution of termite 

eusociality cannot be divorced from an entire suite of interrelated 

and influential morphological, behavioral, developmental, 

and life history characteristics. These include 

monogamy, altricial offspring, adult longevity, 

extended developmental periods, multiple relationships 

with microbial symbionts, proctodeal trophallaxis and 

other food-sharing behaviors, reproduction and development 

that closely track nutritional status, and semelparity 

with age differentials within the brood (Nalepa, 1984, 

1994). So many conditions were interrelated, aligned, and 

influential in the transition that any attempt to reduce an 

explanation to a few basic elements is an oversimplification. 

It is important to note, however, that in integrated 

character sets such as these, selection on just one 

character can lead to changes in associated characters, 

and these changes can occur with a minimum of genetic 

change. It is in this manner that paedomorphic evolution 

often proceeds, with small tweaks in regulatory genes that 

result in maximum impact on an evolutionary trajectory 

(Gould, 1977; Futuyma, 1986; Stanley, 1998). It is also notable 

that all ground plan elements are found among extant 

cockroaches, and that the core process, as in other social 

insects (Hunt and Nalepa, 1994; Hunt and Amdam, 

2005), is a shift in life history characters mediated by a 

nutrient-dependent switch. 

164 COCKROACHES

TEN 

Ecological Impact 

Is there nothing to be said about a cockroach which 

is nice? 

It must have done a favor for somebody once or twice. 

No one will speak up for it in friendly conversations. 

Everyone cold-shoulders it except for its relations. 

Whenever it is mentioned, people’s faces turn to ice. 

Is there nothing to be said about the cockroach 

which is nice? 

—M.A. Hoberman, “Cockroach” 

As a whole, cockroaches are considered garbage collectors in terrestrial ecosystems. They 

recycle dead plants, dead animals, and excrement, processes that are critical to a balanced 

environment. Here we describe some mechanisms by which cockroaches contribute to 

ecosystem functioning via the breakdown of organic matter and the release of nutrients. 

We also summarize their ecological impact on numerous floral, faunal, and microbial 

components of the habitats in which they live, on a variety of scales ranging from the 

strictly local to the global. 

DETRITIVORY 

Although they are rarely mentioned as such in soil science or ecology texts, the majority 

of cockroach species can be classified as soil fauna (Eisenbeis and Wichard, 1985). Many 

live in the upper litter horizon, some burrow into the mineral soil layer, and still others 

inhabit suspended soils. Cockroaches are also associated with decaying logs and stumps, 

rocks, living trees, and macrofungi, which are physically distinct from, but have biological 

links to, the soil (Wallwork, 1976). In the majority of these habitats, the core cockroach 

diet consists of dead plant material. 

Because all species examined to date have endogenous cellulases (Scrivener and Slaytor, 

1994b; Lo et al., 2000), cockroaches may act as primary consumers on at least some 

portion of ingested plant litter. There is no question, however, that the direct impact of 

any higher-level primary consumer does not rate mention when compared to soil microorganisms, 

which are universally responsible for breaking down complex carbohydrates 

and mineralizing nutrients in plant detritus in all ecosystems. As with other 

arthropod decomposers (Wardle, 2002), then, the most profound impact of cockroaches 

is indirect, and lies in their complex and multipartite interaction with soil microbes. The 

physical boundaries between cockroaches and microbial consortia in soil and plant litter, 

however, are not always obvious (Fig. 5.3), and the relationship is so complex as to 

165

make discrete classifications or discussion of individual 

roles arbitrary. Here we center on how cockroaches alleviate 

factors that constrain microbial decomposition, 

namely, the microbial lack of automotion and their dependence 

on water. 

Although microbial communities account for most 

mineralization occurring in soil, they are dormant the 

majority of the time because of their inability to move toward 

fresh substrates once nutrients in their immediate 

surroundings are exhausted. Macroorganisms such as 

cockroaches remove this limitation on microbial activity 

via their feeding and locomotor activities, by fragmenting 

litter and thereby exposing new substrate to microbial attack, 

and by transporting microbes to fresh food (Lavelle 

et al., 1995; Lavelle, 2002). The physical acts of burrowing 

and channeling cause small-scale spatial and temporal 

variations in microbial processes (Meadows, 1991). 

These, in turn, effect major changes in the breakdown of 

woody debris (Ausmus, 1977) and leaf litter (Anderson, 

1983), and may also influence ecological processes in 

other cockroach habitats such as soil, guano, abandoned 

termite nests, and the substrate under logs, bark, and 

stones. In addition to making substrate available for microbial 

colonization via physical disturbance and fragmentation, 

cockroaches transport soil microbes by carrying 

them in and on their bodies. This is particularly 

important in surface-foraging species that diurnally or 

seasonally take shelter under bark, in crevices, or in voids 

of rotting logs, where they inoculate, defecate, wet surface 

wood, affect nitrogen concentration, and contribute to 

bark sloughing (Wallwork, 1976; Ausmus, 1977). 

A second factor that limits microbial decomposers is 

dependence on water (Lavelle et al., 1995). Cockroaches 

and other detritivores are able to mitigate this constraint, 

as the gut provides a moist environment for resident and 

ingested microbes. The hindgut also furnishes a stable 

temperature and pH, and a steady stream of fragmented, 

available substrate. In short, the detritivore gut provides 

an extremely favorable habitat if ingested microbes can 

elude the digestive mechanisms of the host. Fecal pellets, 

the end products of digestion, are similarly favorable 

habitats for microorganisms. Cockroaches on the floor 

of tropical forests consume huge quantities of leaf litter 

(Bell, 1990), thereby serving as mobile fermentation 

tanks that frequently and periodically dispense packets of 

microbial fast food. This alteration in the timing and spatial 

pattern of microbial decomposition may dramatically 

influence the efficient return of above-ground primary 

production to the soil. Fecal pellets also provide food for 

a legion of tiny microfauna, including Collembola, mites, 

protozoa, and nematodes. These feed on the bacteria and 

fungi growing on the pellets, as well as the fluids and 

metabolites resulting from excretory activity (Kevan, 

1962). 

Forests 

In temperate climates, cockroaches are usually relegated 

to a minor role in soil biology because population densities 

can be low (e.g., Ectobius spp. in central Europe— 

Eisenbeis and Wichard, 1985). Similarly, in surveys of 

tropical forest litter, ants, mites, and springtails typically 

dominate in number, with cockroaches rating an incidental 

mention (e.g., Fittkau and Klinge, 1973). Cockroaches 

comprised just 3.0% of the arthropod biomass of 

the ground litter in a humid tropical forest in Mexico 

(Lavelle and Kohlmann, 1984), for example. On the other 

hand, cockroaches are very common in the leaf litter on 

the floor of the Pasoh Forest in West Malaysia, with 6.7 

insects/m 2 (Saito, 1976). They are very well represented 

in several forest types in Borneo. Leakey (1987) cites a 

master’s thesis by Vallack (1981) in which litter invertebrates 

were sampled in four forest types at Gunung Mulu 

in Sarawak. Cockroaches contributed an impressive 43% 

of the invertebrate biomass in alluvial forest, 33% in 

dipterocarp forest, 40% in heath forest, and 2% in a 

forest situated on limestone. A specific decomposer role 

has been quantitatively established for Epilampra irmleri 

in Central Amazonian inundation forests (Irmler and 

Furch, 1979). This species was estimated to be responsible 

for the consumption of nearly 6% of the annual leaf 

litter input. Given that seven additional cockroach species 

were noted in this habitat, the combined impact on decompositional 

processes may be considerable. 

The ecological services of cockroaches are not limited 

to plant litter on the soil surface. Those species found in 

logs, treeholes, standing dead wood and branches, birds’ 

nests, and plant debris trapped in epiphytes, lichens, 

mosses, and limb crotches in the forest canopy (i.e., suspended 

soils) are also members of the vertically stratified 

decomposer niche (Swift and Anderson, 1989). Cockroach 

species that feed on submerged leaf litter on stream 

bottoms and in tank bromeliads may have an impact in 

aquatic systems. 

Wood Feeders 

Wood-feeding cockroach species remove large quantities 

of wood from the surface but their contribution to soil 

fertility has yet to be explored. Both Panesthiinae and 

Cryptocercidae progressively degrade the logs they inhabit. 

They not only ingest wood, but also shred it without 

consumption when excavating tunnels. The abundant 

feces line galleries, pack side chambers, and are 

166 COCKROACHES

Fig. 10.1 Decomposition of logs by Cryptocercus punctulatus, 

Mountain Lake Biological Station, Virginia. (A) Frass pile outside 

gallery entrance. (B) Small log hollowed and filled entirely 

with frass and fecal pellets. Photos by C.A. Nalepa. 

pushed to the outside of the logs, no doubt influencing 

local populations of bacteria, fungi, and microfauna (Fig. 

10.1). The typically substantial body size of these insects 

contributes to their impact; some species of Panesthia exceed 

5 cm in length (Roth, 1979c). Although these two 

taxa are the best known, many cockroach species potentially 

influence log decomposition (Table 3.2). 

Xeric Habitats 

Cockroaches are known to participate in the breakdown 

of plant organic matter in deserts and other arid and 

semiarid landscapes, and have a direct and substantial 

impact on nutrient flow. Anisogamia tamerlana is the 

main consumer of plant litter in Turkmenistan deserts 

(Kaplin, 1995), and cockroaches in the genus Heterogamia 

are the most abundant detritivore in the Mediterranean 

coastal desert of Egypt. The latter dominate the 

arthropod fauna living beneath the canopy of desert 

shrubs, with up to 116,000 cockroaches/ha, comprising 

82% of the arthropod biomass (Ghabbour et al., 1977; 

Ghabbour and Shakir, 1980). The daily food consumption 

of An. tamerlana is 17–18% of their dry body mass, 

with 57–69% assimilation. Females and juveniles consume 

840–1008 g/ha dry plant debris and produce 259– 

320 g/ha of excrement (Kaplin, 1995). These cockroaches 

improve the status of desert soils via their abundant fecal 

pellets, the nitrogen content of which is 10 times that of 

their leaf litter food source (El-Ayouty et al., 1978). 

Many of the ground-dwelling, wingless cockroaches of 

Australia are important in leaf litter breakdown. This is 

particularly true in stands of Eucalyptus, where litter production 

is high relative to other forest types, leaves decompose 

slowly, and more typical decomposers such as 

earthworms, isopods, and millipedes are uncommon 

(Matthews, 1976). The beautiful Striped Desert Cockroach 

Desmozosteria cincta, for example, lives among 

twigs and branches at the base of eucalypts (Rentz, 1996). 

In hummock grasslands and spinifex, genera such as 

Anamesia feed on the dead vegetation trapped between 

the densely packed stems (Park, 1990). The litter-feeding, 

soil-burrowing Geoscapheini are associated with a variety 

of Australian vegetation types ranging from dry sclerophyll 

to rainforest, and have perhaps the most potential 

ecological impact. First, they drag quantities of leaves, 

twigs, grass, and berries down into their burrows, thus 

moving surface litter to lower soil horizons. Second, they 

deposit excreta deep within the earth. Fecal pellets are 

abundant and large; those of Macropanesthia rhinoceros 

are roughly the size and shape of watermelon seeds. 

Third, burrowing by large-bodied insects such as these 

has profound physical and chemical effects on the soil. 

Burrows influence drainage and aeration, alter texture, 

structure, and porosity, mix soil horizons, and modify 

soil chemical profiles (Anderson, 1983; Wolters and 

Ekschmitt, 1997). The permanent underground lairs of 

M. rhinoceros have plastered walls and meander just beneath 

the soil surface before descending in a broad spiral 

(Fig. 10.2). The deepest burrows can be 6 m long, reach 1 

m below the surface, and have a cross section of 4–15 cm. 

Burrows may be locally concentrated; the maximum density 

found was two burrows/m 2 , with an average of 0.33/ 

m 2 (Matsumoto, 1992; Rugg and Rose, 1991). 

Cockroaches in arid landscapes nicely illustrate two 

subtleties of the ecological role of decomposers: first, an 

often mutualistic relationship with individual plants, and 

second, the key role of gut microbiota. In sparsely vegetated 

xeric habitats, the density of cockroaches generally 

varies as a function of plant distribution. In deserts, 

Polyphagidae are frequently concentrated under shrubs 

(Ghabbour et al., 1977), and the burrows of Australian 

Geoscapheini are often associated with trees. Macropanesthia 

heppleorum tunnels amid roots in Callitris- 

Eucalyptus forest, and Geoscapheus woodwardi burrows 

are located under overhanging branches of Acacia spp. in 

mixed open forest (Roach and Rentz, 1998). Not only are 

ECOLOGICAL IMPACT 167

Fig. 10.2 Burrow of Macropanesthia rhinoceros. Although it does not descend deeper than about 

1 m, the gently sloping spiral may be up to 6 m long. Near the bottom the tunnel widens to become 

a nesting chamber to rear young and to cache dried leaves. Drawing by John Gittoes, courtesy 

of Australian Geographic. 

these cockroaches ideally located to collect plant litter, 

they are also positioned to take advantage of the shade, 

moisture retention, and root mycorrhizae provided by 

the plant. Reciprocally, the burrowing, feeding, and excretory 

activities of the cockroaches influence patterns of 

aeration, drainage, microbial performance, decomposition, 

and nutrient availability in the root zone of the 

plants (Anderson, 1983; Ettema and Wardle, 2002). This 

mutualistic relationship therefore may allow for peak 

performance by both parties in a harsh environment. It is 

a tightly coordinated positive feedback system in which 

decomposers improve the quantity and quality of their 

own resource (Scheu and Setälä, 2002). 

Another alliance of ecological consequence occurs at a 

much smaller scale. Because the activity of soil microbes 

is dependent on water, decomposition in deserts occurs 

in pulses associated with precipitation. Ciliates, for example, 

occur in the soil in great numbers, but are active 

only in moisture films. As a consequence, microorganisms 

remain dormant most of the time and plant litter 

accumulates in deserts, restricting nutrient flow (Kevan, 

1962; Taylor and Crawford, 1982). A significant resolution 

to this bottleneck lies in the digestive system of detritivores 

such as cockroaches. The gut environment 

allows for a relatively continuous rate of microbial activity, 

even during periods inimical to decomposition by 

free-living microbes in soil and litter. This relationship is 

present wherever cockroaches feed, but has a profound 

168 COCKROACHES

ecological significance in deserts and other extreme environments 

because it allows for decomposition during periods 

when it would not normally occur—in times of 

drought or excessive heat or cold (Ghabbour et al., 1977; 

Taylor and Crawford, 1982; Crawford and Taylor, 1984). 

Significance of Cockroaches as Decomposers 

The importance of plant litter decomposers to soil formation 

is unquestioned (Odum and Biever, 1984; Vitousek 

and Sanford, 1986; Whitford, 1986; Swift and Anderson, 

1989; Meadows, 1991). Soils in turn provide an 

array of ecosystem services that are so fundamental to life 

that their total value could only be expressed as infinite 

(Daily et al., 1997). Detailing the contribution of cockroaches 

relative to other decomposers, however, is difficult. 

First, information is scarce. For any given ecosystem, 

it is the decomposers that receive the least detailed 

attention. Second, like most decomposers, cockroaches 

are so adaptable that they often do not have well defined 

ecological roles; functional redundancy among detritivores 

is high (Scheu and Setälä, 2002). Third, because of 

the intricate synergistic and antagonistic interactions 

among diverse bacteria, fungi, and invertebrates, decomposition 

is manifested in scales of space and time not easily 

observed or quantified. Decomposition occurs both 

internal and external to the gut, and at microscopic spatial 

scales. It operates via the creation of physical artifacts, 

like burrows and fecal pellets, which accumulate and continue 

to function in the absence of their creators. Effects 

can be localized and short term, or wide ranging and extended 

in time; wood decomposition in particular is a 

very long-term stabilizing force in forest ecosystems (Anderson 

et al., 1982; Anderson, 1983; Swift and Anderson, 

1989; Wolters and Ekschmitt, 1997; Wardle, 2002). 

Other problems in attempting to quantify the role of 

arthropods in decompositional processes are related to 

sampling bias; no one method works best for all groups 

and all soils (Wolters and Ekschmitt, 1997). The results of 

pitfall trapping, for example, can be difficult to interpret. 

No cockroaches were taken in unbaited pitfall traps in 

four habitats in Tennessee, but traps attracted quite a 

number of blattellids when bait (cornmeal, cantaloupe, 

fish) was added (Walker, 1957). Surface-collecting methodology 

such as soil and litter cores may not account for 

cockroach species that are only active after seasonal precipitation 

or those that shelter under bark, under stones, 

or in other concealed locations during the day. Sampling 

techniques for canopy arthropods also have methodological 

biases with regard to a given taxon, particularly those 

species in suspended soils and those that are seasonally 

present. Diurnal, seasonal, and spatial aggregation further 

complicate the proper estimation of abundance 

(Basset, 2001). 

Members of the blattoid stem group undoubtedly 

played a major role in plant decomposition during the 

Paleozoic (Shear and Kukalová-Peck, 1990). The ecological 

significance of extant cockroaches, however, is usually 

assumed to be negligible (Kevan, 1993) because of their 

often low numbers during surveys (e.g., some Australian 

studies—Postle, 1985; Tanton et al., 1985; Greenslade and 

Greenslade, 1989). If considered in terms of biomass, 

however, their importance is magnified because of large 

individual body size relative to many other detritivores 

such as mites and Collembola. Basset (2001), in a review 

of studies conducted worldwide, concluded that cockroaches 

dominated in canopies, comprising an astonishing 

24.3% of the invertebrate biomass (discussed in 

Chapter 3). The clumped distribution and social tendencies 

of many species also tends to increase their ecological 

impact. Cockroaches that aggregate in tree hollows, 

for example, directly benefit their host plant, as defecation 

steadily fertilizes the soil at the base of the tree 

(Janzen, 1976). Large, subsocial or gregarious woodfeeding 

cockroaches may be able to pulverize logs on a 

time scale comparable to, if not better than, termites. In 

this regard, several studies in montane environments report 

that cockroach population levels in plant litter are 

negatively correlated with the presence of termites, a 

group that strongly and predominantly influences the 

pattern of decomposition processes and whose ecological 

importance is clear. Surveys on Mt. Mulu in Sarawak, 

Borneo, indicate that the density of soil- and litterdwelling 

termites declines with altitude (Collins, 1980). 

Cockroaches were present in low numbers at all altitudes, 

but individuals were larger and more numerous in upper 

montane forests, where they constituted 40% of the total 

macrofauna biomass. Rhabdoblatta was the most common 

genus at upper altitudes, found in all plots from 

1130 m upward, but not below. The Cryptocercus punctulatus 

species complex dominates the saproxylic guild in 

the Southern Appalachian Mountains, and occupies the 

same niche as does the subterranean termite Reticulitermes 

at lower elevations (Nalepa et al., 2002). The same 

altitudinal trend was evident in soil and litter core samples 

taken on Volcán Barva in Costa Rica; the biomass of 

cockroaches fluctuated, but generally increased with altitude. 

Termites were not found above 1500 m, but cockroaches 

made up 61% of the biomass at that altitude 

(Atkin and Proctor, 1988). On Gunung Silam, a small 

mountain in Sabah, the altitudinal associations were reversed. 

At 280 m, cockroaches were 84% of the invertebrate 

biomass and termites were not found; at 870 m, termites 

were 25% of the biomass, while cockroaches were 


1% (Leakey, 1987, Table 3). The reasons for these altitudinal 

changes in distribution were not causally related 

to measured changes in other site properties such as forest 

structure and soil organic matter in the Costa Rican 

study (Atkin and Proctor, 1988). 

POLLINATION 

Cockroaches are frequently observed on flowers and 

many readily feed on offered pollen and nectar (Roth and 

Willis, 1960). In temperate zones, Blattaria are only occasionally 

reported from blossoms. Ectobius lapponicus and 

E. lividus have been observed on flowers of the genera 

Spirea, Filipendula, and Daucus in Great Britain (Proctor 

and Yeo, 1972), and Latiblattella lucifrons feeds on pollen 

of Yucca sp. in southern Arizona (Ball et al., 1942). 

Nymphs of Miriamrothschildia notulatus and Periplaneta 

japonica and brachypterous adults of Margattea satsumana 

visit extrafloral nectaries at the base of fleshy, 

egg-like inflorescences of the low-growing root parasite 

Balanophora sp. on the floor of evergreen forests in Japan. 

Visits corresponded with cycles of evening nectar secretion, 

multiple plants were visited in succession, and 

pollen grains were observed attached to the tarsi and 

mouthparts of Mar. satsumana. All observed cockroaches, 

however, are flightless, suggesting to the authors that 

cross-pollination is unlikely to be effective (Kawakita and 

Kato, 2002). An association between cockroaches and 

flowering plants may be more widespread in the tropics. 

The strikingly colored Paratropes bilunata visits flowers of 

the Neotropical (Costa Rica) canopy species Dendropanax 

arboreus (Araliaceae). Cockroaches were observed 

flying during the day to successive inflorescences located 

34 m above the ground, ignoring nearby flowers of a different 

species. The exposed condition of the anthers and 

stigma of D. arboreus and the observed floral fidelity of 

the cockroach suggest that Parat. bilunata is a likely pollinator 

(Perry, 1978; Roth, 1979a). Nagamitsu and Inoue 

(1997) offer more direct evidence that cockroaches can be 

the main pollinators of a plant species in the understory 

of a lowland mixed dipterocarp forest in Borneo. These 

authors observed blattellid cockroaches feeding on pollen 

and stigmatic exudate of Uvaria elmeri (Annonaceae) 

(Fig. 10.3). The visitation time of the cockroaches corresponded 

with nocturnal dehiscence of anthers, and 

pollen grains were observed in both the gut and on the 

undersurface of the head. Because few bees are typically 

found in canopy collections (Basset, 2001), cockroaches 

may be among those arthropods filling the pollinator 

niche in treetops. Of the known cases of cockroach pollination, 

the degree of floral specificity, distances between 

visited inflorescences, and consequent effect on gene flow 

in flowering plants have not been studied. 

Fig. 10.3 Blattellid cockroach nymph feeding on pollen of 

Uvaria elmeri (Annonaceae) in lowland mixed dipterocarp forest 

in Borneo. From Nagamitsu and Inoue (1997). Photo courtesy 

of I. Nagamitsu, with permission of The American Journal 

of Botany. 

FOOD CHAINS 

Although cockroaches generally feed on dead plant and 

animal material, they are also well known as primary consumers. 

Many blattids in tropical forests are cryptic herbivores 

and some are overtly herbivorous, particular on 

young vegetation (Chapter 4). Roth and Willis (1960) 

were surprised that the role of cockroaches as plant pests 

is rarely discussed, and detailed the abundant records of 

the phenomenon in the literature. Most of the evidence 

comes from commercially grown crops, particularly in 

the tropics and in greenhouses. One field study, however, 

found that the frequency of herbivore damage on new 

leaves in rainforest canopy (Puerto Rico) was significantly 

correlated with the abundance of Blattaria (Dial 

and Roughgarden, 1995). It is therefore possible that 

cockroaches may have an undocumented but significant 

ecological and evolutionary impact on vascular tropical 

flora, as well as on nonvascular plants in the phylloplane. 

At the next level of the food chain, cockroaches are prey 

for numerous taxa, including pitcher plants (Sarracenia 

and Nepenthes spp.) (Roth and Willis, 1960) and a variety 

of invertebrate and vertebrate predators (Fig. 10.4). The 

principal food of the grylloblattid Galloisiana kurentzovi 

in East Asia is juveniles of Cryptocercus relictus (Storozhenko, 

1979), and small blattellid cockroaches climbing 

on low vertical twigs and grass blades constitute 92% of 

the prey of the Australian net-casting spider Menneus 

unifasciatus (Austin and Blest, 1979). In desert sand 

dunes of California, Arenivaga investigata makes up 23% 

of the prey biomass taken by the scorpion Paruroctonus 

mesaensis (Polis, 1979). Examination of the excrement of 

170 COCKROACHES

the South American frog Phyllomedusa iheringii indicates 

that cockroaches are a major part of its diet (Lagone, 

1996). Blattellid cockroaches of the genus Parcoblatta are 

a high proportion of the menu of endangered red-cockaded 

woodpeckers (Picoides borealis) in the Coastal Plain 

of South Carolina (Horn and Hanula, 2002). Cockroaches 

were consistently taken by all observed birds, 

made up 50% of the overall diet, and were 69.4% of the 

prey fed to nestlings (Hanula and Franzreb, 1995; Hanula 

et al., 2000). Pycnoscelus indicus on Cousine Island in the 

Seychelles is the favored prey of the endangered magpie 

robin (Copsychus sechellarum) (S. Le Maitre, pers. comm. 

to LMR); the birds feed on American cockroaches as well. 

Attempts to control urban infestations of Periplaneta 

americana with toxic insecticides may have contributed 

to the decline of this species on Frégate Island. The birds 

feed close to human habitations and take advantage of 

dead and dying insecticide-treated cockroaches. Lethal 

doses accumulated in the birds, with subacute effects on 

their behavior. The current use of juvenile hormone 

analogs for cockroach control appears to result in good 

control of the pests while posing a negligible hazard to the 

birds (Edwards, 2004). These few examples (see Roth and 

Willis, 1960 for more) suffice to emphasize that in their 

role as prey, cockroaches may significantly influence the 

population structure of insectivores in terrestrial ecosystems. 

They may also be a link between terrestrial and 

aquatic food chains at river and stream edges, and in delicately 

balanced cave ecosystems. Cave-dwelling cockroaches 

accidentally introduced into water are one of the 

Fig. 10.4 Scorpion feeding on the ground-dwelling cockroach 

Homalopteryx laminata, Trinidad. Photo courtesy of Betty 

Faber. 

principal foods of some cavernicolous fishes; they are 

26% of the diet of Milyeringa veritas (Humphreys and 

Feinberg, 1995). Cockroaches are considered the base of 

the food web in South African bat caves and support a 

large community of predators and parasites. Their feces 

are also an important food source for smaller invertebrates 

(Poulson and Lavoie, 2000). Hill (1981) noted that 

for most of the guano community in Tamana cave, 

Trinidad, the incoming supply of energy was in the form 

of cockroach, not bat, feces. 

At the top of the food chain, there are numerous reports 

of cockroaches preying on other insects (detailed by 

Roth and Willis, 1960). Most of these accounts are observations 

of opportunistic predation on a broad range of 

vulnerable taxa and life stages, particularly eggs and larvae. 

Instances of cockroaches controlling prey populations 

of crickets and bedbugs in urban settings are frequent 

in the historic literature but largely anecdotal and 

unverified. One ecological setting in which cockroaches 

do have potential for influencing population densities of 

prey is in caves (Chapter 4). 

LARGE-SCALE EFFECTS 

Cockroaches potentially influence biogeochemical cycles 

via two known pathways: nitrogen fixation and methane 

production. Cryptocercus is the only cockroach currently 

known to harbor gut microbes capable of fixing atmospheric 

nitrogen (Breznak et al., 1974), but spirochetes 

found in the hindgut of other species also may have the 

ability (Lilburn et al., 2001). Acetylene reduction assays 

indicate that adults and juveniles of Cryptocercus fix nitrogen 

at rates comparable to those of termites on a body 

weight basis (0.01–0.12 mg N day 1 g 1 wet weight) 

(Breznak et al., 1973; Breznak et al., 1974, 1975). The 

process provides a mechanism for nitrogen return to the 

ecosystem and may have a significant ecological impact 

(Nardi et al., 2002), particularly in the food chains of the 

montane mesic forests where Cryptocercus is the dominant 

macroarthropod feeding in rotting logs. 

A more universal characteristic of cockroaches is an association 

with methanogenic bacteria in the hindgut and 

the consequent emission of methane. Almost all tropical 

cockroaches tested emit methane, regardless of the origin 

of specimens and their duration of laboratory captivity. 

Methane, carbon dioxide, and water are released synchronously 

in a resting cockroach, in slow periodic cycles 

that suggest the gases are respired (Bijnen et al., 1995, 

1996). Among temperate species, North American C. 

punctulatus emits the gas (Breznak et al., 1974), but 

the European genus Ectobius does not (Hackstein and 

Strumm, 1994). Cockroaches (n 34 species) produce 

an average of 39 nmol/g methane/h, with a maximum of 


450 nmol/g/h (Hackstein, 1996). On a global scale, estimates 

of methane production by cockroaches vary widely 

and are debatable, given first, the paucity of data on which 

to base biomass estimates of field populations, and second, 

the finding that methane production varies with 

cockroach age and diet fiber content (Gijzen et al., 1991; 

Kane and Breznak, 1991). It has been suggested that cockroaches 

make a significant contribution to global methane, 

particularly in the tropics (Gijzen and Barugahare, 

1992; Hackstein and Strumm, 1994). However, methane 

oxidation by bacteria in the soil may buffer the atmosphere 

from methane production by gut Archaea, and although 

cockroaches may be a gross source of methane, 

little to none of it may be escaping into the atmosphere. 

The sink capacity of the soil may exceed methane production 

by cockroaches, just as it does for termites (Eggleton 

et al., 1999; Sugimoto et al. 2000). Nonetheless, their 

typically large body size (relative to termites), and the tendency 

of many species to live in aggregations in enclosed 

spaces (e.g., treeholes, caves, logs) may engender atmospheric 

changes at a local level. Mamaev (1973), for example, 

collected more than 400 C. relictus from a single 

cedar log. On a per weight basis methane production by 

C. punctulatus is comparable to the termite Reticulitermes 

flavipes and may surpass levels emitted by ruminants 

(Breznak et al., 1974; Breznak, 1975). 

OTHER ROLES 

Cockroaches are part of the guild of arthropods that provide 

waste elimination services; they feed on the fecal material 

of animals in all trophic levels (Roth and Willis, 

1957). While this behavior is most often noted in relation 

to disease transmission by pest species, it is likely that 

cockroaches also contribute to the rapid processing of excrement 

in natural settings (Fig. 5.2). Cockroaches habitually 

found in bird nests, mammal burrows, and the middens 

of social insects provide nest sanitation services for 

their hosts. MacDonald and Matthews (1983) suggest 

that nymphs of Parcoblatta help prolong the colony cycle 

of southern yellowjackets (Vespula squamosa) by scavenging 

colony debris and keeping fungal and protozoan 

populations suppressed. Cockroaches (probably Periplaneta 

fuliginosa) are frequently found in honeybee hives in 

North Carolina; their role in hive sanitation merits further 

investigation (D.I. Hopkins, pers. comm. to CAN). 

In addition to acting as predators, prey, and regulators 

of microbial processes, cockroaches have ecological relationships 

with a variety of micro- and macrofauna. These 

include ecto- and endoparasites, parasitoids, and commensals 

(mites, for example). The burrows and tunnels of 

cockroaches that excavate solid substrates often serve as 

shelter for many additional tenants. The burrows of M. 

rhinoceros harbor a complex of other cockroaches (Calolampra 

spp., among others), beetles, silverfish, centipedes, 

frogs, and moths (Park, 1990; Rugg and Rose, 1991). One 

scarab (Dasygnathus blattocomes) has been collected nowhere 

else (Carne, 1978). Salamanders, centipedes, ground 

beetles, and springtails are frequently found in the galleries 

of C. punctulatus (Cleveland et al., 1934; CAN, unpubl.). 

Within the human realm, cockroaches have both cultural 

and scientific significance. Several species are used 

as pets and pet food (McMonigle and Willis, 2000), and 

because they are robust under taxing conditions they 

make excellent fish bait. Urban pests serve as ideal subjects 

for a wide range of scientific studies. They are easily 

fed on commercially available pet chow, do not mind a 

dirty cage, withstand and even thrive under crowded conditions, 

and are prolific breeders. The relatively large size 

of some (e.g., Periplaneta) facilitates tissue and cell extraction, 

and their sizable organs are easily pierced with 

electrodes or cannulae. The cockroach nervous system is 

less cephalized than in many insects, making these insects 

excellent experimental models in neurobiology; two volumes 

have been written on the subject (Huber et al., 

1990). Their overall lack of specialization makes them 

ideal for teaching students the basics of insect anatomy. 

They also readily lend themselves to laboratory experiments 

on the physiology of reproduction, nutrition, respiration, 

growth and metamorphosis, regeneration, chemical 

ecology, learning, locomotion, circadian rhythms, and 

social behavior (Bell, 1981, 1990). Therapeutic concoctions 

that include cockroaches are frequently cited in 

medical folklore, and their use as a diuretic has received 

some clinical support. Roth and Willis (1957) list 30 

specific diseases and disorders where cockroaches have 

featured in treatment. When American jazz legend Louis 

Armstrong was a child, his mother fed him a broth made 

from boiled cockroaches whenever he was ill (Taylor, 

1975). In southern China and in Chinatown in New York 

City, dried specimens of Opisthoplatia orientalis are still 

sold for medicinal purposes (Roth, 2003a), and Blatta orientalis 

is marketed on the Internet as a homeopathic 

medicine. Cockroaches produce a wide range of pheromones 

and defensive compounds, and may be rewarding 

subjects for pharmaceutical bioprospecting. Given the 

close association of cockroaches with rotting organic 

matter, a search for antimicrobials may be particularly 

fruitful (Roth and Eisner, 1961). The secretions used by 

some oviparous species to attach their oothecae to objects 

have been likened to superglue, as attempting to remove 

the egg cases either ruptures them or also pulls up the 

substrate (Edmunds, 1957; Deans and Roth, 2003). Cock- 

172 COCKROACHES

oach guts, like termite guts (Ohkuma, 2003), may be a 

source of novel microorganisms with wide-ranging industrial 

applications. 

CONSERVATION 

Cockroaches are not generally considered a charismatic 

taxon; species that are threatened with extinction are unlikely 

to rally conservationists to action. They are nonetheless 

an integral part of a stable and productive ecosystem 

in tropical rainforest and other habitats. Cockroaches 

deserve our consideration and respect for the range of 

services they perform and for their membership in an 

intricate web of interdependent and interacting flora, 

fauna, and microbes. Many cockroach species live in 

habitats of conservation concern and are threatened by 

canopy removal, urbanization, and agricultural practices. 

Philopatric species with naturally small population sizes 

and specific habitat requirements are particularly vulnerable 

to perturbations (Pimm et al., 1995; Tscharntke et al., 

2002; Boyer and Rivault, 2003). These taxa are frequently 

wingless, and their consequent low dispersal ability 

makes them vulnerable to habitat fragmentation and genetic 

bottlenecks. Several species of Australian burrowing 

cockroaches have restricted ranges and are affected by 

farming/forestry practices or by urbanization. The accompanying 

soil disturbance, soil compaction, and loss of 

their leaf litter food sources have devastated some populations 

of these unique insects (H.A. Rose, pers. comm. to 

CAN). 

Caves are delicately balanced and vulnerable ecosystems 

whose resident cockroaches can be severely affected 

by guano compaction, guano collection, and other human 

disturbances (Braack, 1989). Nocticola uenoi miyakoensis, 

for example, became rare in the largest known 

limestone cave on Miyako-jima Island after it was opened 

to tourists (Asahina, 1974), and the invertebrate community 

of an Australian cave disappeared due to soil compaction 

by human visitors (Slaney and Weinstein, 1997a). 

According to Gordon (1996), the cave-dwelling species 

Aspiduchus cavernicola (Tuna Cave cockroach) living in a 

network of caves in southern Puerto Rico is officially 

classified as a “species at risk”by the U.S. Fish and Wildlife 

Service. Roth and Naskrecki (2003) recently described a 

new species of cave cockroach collected during a Conservation 

International survey of West African sites under 

threat from large-scale mining operations. The removal 

of cave cockroaches for scientific study also can have a 

significant impact on their populations (Slaney and Weinstein, 

1997a). 

Global warming and the resultant decrease in snow 

cover at high elevations may put cockroaches such as the 

New Zealand alpine species Celatoblatta quinquemaculata 

at risk (Sinclair, 2001). Although the species is physiologically 

protected against the cold, it relies on the thermal 

buffering effect of snow cover in particularly harsh 

winters. Reduced snow cover results in an increased number 

of freeze-thaw cycles and lower absolute minimum 

temperatures, making the “mild” winter more, rather 

than less, stressful to the insect. 

Wood-feeding and other log-dependent cockroaches 

(Table 3.2) are sensitive to the ecological changes brought 

about by both modern forestry and human settlement 

and, like many saproxylic arthropods (Grove and Stork, 

1999; Schiegg, 2000), may be used as habitat continuity 

indicators in ecological assessment. These insects rely on 

a resource whose removal from the ecosystem is the usual 

objective of forest management (Grove and Stork, 1999) 

and compete with lumber companies (Cleveland et al., 

1934) and resident humans who prize coarse woody debris 

as fuel and building material. Wood-feeding cockroaches 

may survive canopy removal and subsequent desiccating 

conditions if logs of a size sufficient to provide a 

suitable microhabitat are left on the ground. Cryptocercus 

primarius, for example, has been collected from largediameter 

logs in young re-growth forest in China (Fig. 

10.5). More often, however, coarse woody debris left on 

the forest floor after logging operations is gathered and 

used as fuel (Nalepa et al., 2001b). Based on the work of 

Harley Rose (University of Sydney), the endemic Lord 

Howe Island wood-feeding cockroach Panesthia lata was 

recently listed by the New South Wales Scientific Committee 

as an endangered species (Adams, 2004). It has not 

been found on Lord Howe Island since the 1960s, probably 

because of rats introduced in 1918. Small numbers of 

the cockroach were recently discovered on Blackburn Island 

and Roach Island. 

Litter-dwelling cockroaches can be sensitive habitat indicators. 

The Russian cockroach Ectobius duskei, normally 

found at levels of up to 10 individuals/m 2 in undisturbed 

steppe, disappears if these grasslands are plowed 

to grow wheat. If the fields are allowed to lie fallow, the 

cockroaches gradually become reestablished (Bei-Bienko, 

1969, 1970). Although the species has been eliminated in 

intensely cultivated areas, a 1999 study found E. duskei 

well represented in the leaf litter of steppe meadows in the 

Samara district (Lyubechanskii and Smelyanskii, 1999). 

The effect of disturbance on litter invertebrates depends 

not only on the type of disturbance, but also on 

site-specific factors. In the dry Mediterranean-type climate 

of western Australia cockroaches appear resilient to 

moderate disturbances. Cockroach numbers and species 

richness as measured by pitfall traps declined significantly 

after logging and fire, yet recovered within 48 mon. 


lattellids, from his 0.65 ha of rainforest in Kuranda, 

Queensland (elev. 335 m asl). In one light trap study in 

Panama, 42% of 164 species captured were new to science 

(Wolda et al., 1983). 

NEGATIVE IMPACT OF COCKROACHES 

Fig. 10.5 Li Li, Chinese Academy of Science, Kunming, and 

Wang De-Ming, Forest Bureau, Diqing Prefecture, opening a 

rotted log containing Cryptocercus primarius in a young regrowth 

spruce and fir forest at Napa Hai, Zhongdian Co., Yunnan 

Province, China. The cockroaches were found in large logs 

left on the forest floor after the forest was harvested; maximum 

regrowth was 10 cm in diameter. This site was immediately adjacent 

to a mature coniferous forest with logs also harboring 

the cockroach. Photo by C.A. Nalepa. 

The insects showed no significant response to habitat 

fragmentation and livestock activity, but were most diverse 

where forest litter was thickest. The authors explain 

their results in terms of the fire ecology of the area. In seasonally 

dry habitats cockroaches appear to have a high degree 

of tolerance to recurrent disturbances and may aestivate 

in burrows or under bark during harsh conditions 

(Abenserg-Traun et al., 1996b; Abbott et al., 2003). There 

is a distinction, however, between cockroaches adapted to 

these habitats and those residing where the ecological 

equilibrium is much more precarious. Tropical rainforests, 

where the vast majority of cockroaches live, are 

under heavy assault (Wilson, 2003), and large numbers of 

described and undescribed species are being lost along 

with the natural greenhouses in which they dwell. Grandcolas, 

for example, estimated 181 cockroach species in a 

lowland tropical forest in French Guiana, with 67 species 

active in the understory during night surveys in one site 

(Grandcolas, 1991, 1994b). David Rentz (pers. comm. to 

CAN) has recorded 62 species of cockroaches, mostly 

The negative impact of cockroaches introduced into 

non-native habitats is well documented. The handful of 

species that have invaded the man-made environment 

have had enormous economic significance as pests, as 

sources of allergens, as potential vectors of disease to humans 

and their animals, and as intermediate hosts for 

some parasites, such as chicken eye-worms. Exotic cockroaches 

have also been introduced into natural non-native 

ecosystems like caves (Samways, 1994) and islands, 

such as the Galapagos (Hebard, 1920b). In a survey of La 

Réunion and Mayotte in the Comoro Islands, 21 cockroach 

species were found, with introduced species more 

common than endemic species that use the same habitats. 

The abundant leaf litter and loose substrate typical of 

cultivated land was favorable habitat for the adventive 

species, particularly in irrigated plots (Boyer and Rivault, 

2003). The Hawaiian Islands have no native cockroaches, 

but 19 introduced species (Nishida, 1992). Periplaneta 

americana has invaded a number of Hawaiian caves, and 

is thought to have contributed to the decline of the Kauai 

cave wolf spider (Adelocosa anops) by affecting its chief 

food source, cave amphipods. The cockroach opportunistically 

preys on immature stages of the amphipods, 

and competes with older stages at food sources (Clark, 

1999). In Florida, laboratory studies indicate that the 

Asian cockroach Blattella asahinai may disrupt efforts to 

control pest aphids with parasitic wasps by feeding on 

parasitized aphid “mummies” (Persad and Hoy, 2004). 

Although this problem occurred primarily when the 

cockroaches were deprived of food for 24 hr, the high 

populations of Asian cockroaches that can occur in citrus 

orchards (up to 100,000/ha) (Brenner et al., 1988) guarantee 

that some are usually hungry. 

OUTLOOK 

The meager information we currently have on cockroach 

activities in natural habitats suggests that they may be key 

agents of nutrient recycling in at least some desert, cave, 

and forest habitats. They comprise the core diet for a variety 

of invertebrate and vertebrate taxa, and may play 

some role in pollination ecology, particularly in tropical 

canopies. Before we can begin to document and quantify 

their ecosystem services, however, more time, energy, and 

financial resources must be devoted to two specific areas 

of cockroach research. 

174 COCKROACHES

The first and most obvious requirement is for basic information 

on the diversity, abundance, and biology of 

free-living species, as cockroaches remain a largely uninvestigated 

taxon. In 1960, Roth and Willis indicated that 

there were 3500 described species and estimated an additional 

4000 unnamed species. Currently, most estimates 

are in the range of 4000 to 5000 living cockroaches, with 

at least that many yet to be described. Some of the most 

diverse families, such as Blattellidae, are strongly represented 

in tropical climes but very poorly studied (Rentz, 

1996). Among described species, the observation by Hanitsch 

(1928) that “the life history of the insect begins in 

the net and ends in the bottle” still holds true for the vast 

majority. Core data on cockroach biology are derived 

nearly exclusively from insects that have been reared in 

culture and studied in the laboratory. How closely the results 

of these studies relate to Blattaria in natural habitats 

is in many cases questionable. Laboratory-reared cockroaches 

are domesticated animals typically kept in mixed 

sex, multiage groups within restricted, protected enclosures, 

and supplied with a steady, monotonous food 

source, ad lib water, and readily accessible mating partners. 

Most tropical species cultured in the United States 

are derived from just a few sources collected decades ago 

(LMR, pers. obs.), and are therefore apt to be lacking the 

variation expressed in free-living populations. The group 

dynamics (Chapter 8), locomotor ability (Akers and Robinson, 

1983; Chapter 2), and fecundity (Wright, 1968) of 

laboratory cockroaches are known to differ from that of 

wild strains, and crowded rearing conditions and the inability 

to emigrate can result in artificially elevated levels 

of density-dependent behaviors such as aggression and 

cannibalism. Mira and Raubenheimer (2002) compared 

laboratory-reared P. americana to “feral” animals loose in 

their laboratory building and found that the free-range 

cockroaches had higher growth rates, additional nymphal 

stadia, greater resistance to starvation, and a higher 

numbers of endosymbiotic bacteria in the fat body. Field 

studies and experiments that incorporate a realistic simulation 

of field conditions are clearly desirable, incorporating 

as wide a range of taxa and habitat types as possible. 

A small army of eager young nocturnal scientists, and 

perhaps octogenarians, who cannot sleep anyway (LMR, 

pers. obs.), need to consider cockroaches as worthy subjects 

of observation and experimentation under natural 

conditions. 

A second requisite for progress lies in bankrolling the 

training of a new generation of cockroach systematists, a 

need made especially acute with the passing of the second 

author of this volume (CAN, pers. obs.). Field studies will 

have little value if the subject of research efforts cannot be 

identified, or if collected vouchers languish undescribed 

in museum drawers. One of LMR’s final publications 

sounded the call for “true systematists interested in studying 

the biology and classification of cockroaches,”but recommended 

that “he or she marry a wealthy partner” 

(Roth 2003c). 

Even if these two requirements are in some small measure 

met, progress in evaluating the ecological impact of 

cockroaches may be hindered unless we recognize the 

need for some attitudinal shifts in our approach to cockroach 

studies. First, evaluation of the role of cockroaches 

in the nutrient cycles of ecosystems demands a microbially 

informed perspective (Chapter 5). Relationships 

with microorganisms as food, on food, transient through 

the digestive tract, and resident in and on the body not 

only form the functional basis of cockroach performance 

on a plant litter diet, but also direct their impact on decompositional 

processes. Second, it might behoove us to 

keep the phylogenetic and ecological relationships of 

cockroaches and termites in mind when attempting to assess 

the role of Blattaria in ecosystems. Sampling and 

evaluation techniques employed in termite studies (e.g., 

Bignell and Eggleton, 2000) may also prove useful in 

studying their cryptic cockroach relatives. Scattered hints 

in the literature that the two taxa may be ecologically displacing 

each other in selected habitats would be well 

worth characterizing and quantifying. Third, and finally, 

as biologists we have a responsibility to help alter the 

lenses through which potential students as well as the 

general public characteristically regard the subjects of this 

book. A realistic image with which to begin public relations 

is that of inconspicuous workhorses, acting beneath 

the radar to move nutrients through the food web, maintain 

soil fertility, and support a variety of the complex and 

cascading processes that sustain healthy ecosystems. 



Appendix 

Assignation of the cockroach genera discussed in the text to superfamily, family, and subfamily; 

after Roth (2003c) unless otherwise indicated. 

Blattoidea 

Blattidae 

Archiblattinae 

Archiblatta 

Blattinae 

Blatta, Cartoblatta, Celatoblatta, Deropeltis, Eumethana, Hebardina, Neostylopyga, 

Pelmatosilpha, Periplaneta, Pseudoderopeltis 

Lamproblattinae 

Lamproblatta 

Polyzosteriinae 

Anamesia, Desmozosteria, Eurycotis, Euzosteria, Leptozosteria, Platyzosteria, 

Polyzosteria, Zonioploca 

Tryonicinae 

Angustonicus, Lauraesilpha, Methana, Pallidionicus, Pellucidonicus, Punctulonicus, 

Rothisilpha, Scabina, Tryonicus 

177

Blaberoidea 

Otherwise unplaced: Neopolyphaga a 

Polyphagidae 

Subfamily undetermined 

Compsodes, Heterogamia, b Homopteroidea, 

Leiopteroblatta, Myrmecoblatta, Oulopteryx, Tivia 

Polyphaginae 

Anisogamia, Arenivaga, Austropolyphaga, 

Eremoblatta, Ergaula, Eucorydia, Eupolyphaga, 

Heterogamisca, Heterogamodes, Holocampsa, 

Homoeogamia, Hypercompsa, Polyphaga, 

Polyphagoides, Therea 

Cryptocercidae 

Cryptocercinae 

Cryptocercus 

Nocticolidae 

Alluaudellina, Cardacopsis, Cardacus, 

Metanocticola, Nocticola, Spelaeoblatta, Typhloblatta 

Blattellidae 


Parellipsidion, Sphecophila 

Anaplectinae 

Anaplecta 

Attaphilinae 

Attaphila 

Pseudophyllodromiinae 

Aglaopteryx, Agmoblatta, Allacta, Amazonina, Balta, 

Cariblatta, Chorisoneura, Chorisoserrata, 

Dendroblatta, Ellipsidion, Euphyllodromia, 

Euthlastoblatta, Imblattella, Latiblattella, 

Lophoblatta, Macrophyllodromia, Margattea, 

Mediastinia, Nahublattella, Plecoptera, Prosoplecta, 

Pseudobalta, Riatia, Sliferia, Shelfordina, 

Sundablatta, Supella 

Blattellinae 

Beybienkoa, Blattella, Chorisia, Chromatonotus, 

Escala, Hemithyrsocera, Ischnoptera, Loboptera, 

Lobopterella, Miriamrothschildia, Nelipophygus, 

Neoloboptera, Neotemnopteryx, Neotrogloblattella, 

Nesomylacris, Nondewittea, Parasigmoidella, 

Paratemnopteryx, Parcoblatta, Pseudoanaplectinia, 

Pseudomops, Robshelfordia, Stayella, Symploce, 

Trogloblattella, Xestoblatta 

Ectobiinae 

Choristima, Ectobius, Phyllodromica 

Nyctiborinae 

Megaloblatta, Nyctibora, Paramuzoa, Paratropes 

Blaberidae 

A molecular phylogeny of blaberid subfamilies is given 

in Maekawa et al. (2003, Fig. 3) 


Apotrogia, Compsolampra 

Blaberinae 

Archimandrita, Aspiduchus, Blaberus, Blaptica, 

Byrsotria, Eublaberus, Hyporichnoda, 

Lucihormetica, Monastria, Phoetalia 

Panesthiinae 

Ancaudellia, Caeparia, Geoscapheus, c 

Macropanesthia, c Microdina, Miopanesthia, 

Neogeoscapheus, c Panesthia, Parapanesthia, c 

Salganea 

Zetoborinae 

Capucina, Lanxoblatta, Parasphaeria, Phortioeca, 

Schizopilia, Schultesia, Thanatophyllum 

Epilamprinae 

Aptera, Calolampra, Colapteroblatta, 

Comptolampra, d Dryadoblatta, Epilampra, 

Haanina, Homalopteryx, Litopeltis, Miroblatta, 

Molytria, Opisthoplatia, Phlebonotus, Phoraspis, 

Poeciloderrhis, Pseudophoraspis, Rhabdoblatta, 

Thorax, Ylangella 

Oxyhaloinae 

Elliptorhina, Griffiniella, Gromphadorhina, 

Jagrehnia, Nauphoeta, Princisia, Rhyparobia, 

Simandoa 

Pycnoscelinae 

Pycnoscelus 

Diplopterinae 

Diploptera 

Panchlorinae 

Panchlora 

Perisphaeriinae 

Bantua, Compsagis, Cyrtotria, Derocalymma, Laxta, 

Neolaxta, Perisphaeria, Perisphaerus, Pilema, 

Poeciloblatta, Pseudoglomeris, Trichoblatta 

Gyninae 

Alloblatta, Gyna 

a. According to Jayakumar et al. (2002). 

b. According to Ghabbour et al. (1977). 

c. Tribe Geoscapheini. 

d. After Anisyutkin (1999). 

178 APPENDIX

Glossary 

Accessory gland a secretory organ associated with the reproductive system. 

Acrosome a cap-like structure at the anterior end of a sperm that produces enzymes aiding in 

egg penetration. 

Aerobic growing or occurring in the presence of oxygen. 

Alary pertaining to wings. 

Alate the winged stage of a species. 

Allogrooming grooming of one individual by another. 

Alloparental care care of young dependents by individuals that are not their parents. 

Anaerobic growing or occurring in the absence of oxygen. 

Aphotic without sunlight of biologically significant intensity. 

Aposematic possessing warning coloration. 

Apterous without tegmina or wings. 

Arolium (pl. arolia) an adhesive pad found at the tip of the tarsus, between the claws. 

Autogrooming grooming your own body. 

Batesian mimicry the resemblance of a palatable or harmless species (the mimic) to an unpalatable 

or venomous species (the model) in order to deceive a predator. 

Bootstrap values a measure of the reliability of phylogenetic trees that are generated by cladistic 

methods. 

Brachypterous having short or abbreviated tegmina and wings. 

Brood sac an internal pouch where eggs are incubated in female cockroaches. 

Brooding parental care where the females remain with newly hatched offspring for a short period 

of time, typically just until hardening of the neonate cuticle. 

Bursa in the female, a sac-like cavity that receives the spermatophore during copulation. 

Caudad toward the posterior, or tail end, of the body. 

Cellulase an enzyme capable of degrading cellulose. 

Cellulolytic causing the hydrolysis of cellulose. 

Cellulose a complex carbohydrate that forms the main constituent of the cell wall in most 

plants. 

Cephalic toward the anterior, or head end, of the body. 

Cercus (pl. cerci) paired, usually multi-segmented, sensory appendages at the posterior end of 

the abdomen. 

179

Chemotaxis the directed reaction of a motile organism toward 

(positive) or away from (negative) a chemical stimulus. 

Chitin a polysaccharide constituent of arthropod cuticle. 

Chitinase an enzyme capable of degrading chitin. 

Circadian exhibiting 24-hr periodicity. 

Clade a hypothesized monophyletic group of taxa sharing a 

closer common ancestry with one another than with 

members of any other clade. 

Cladistic analysis a technique in which taxa are grouped 

based on the relative recency of common ancestry. 

Clone the asexually derived offspring of a single parthenogenetic 

female. 

Conglobulation the act of rolling up into a ball. 

Consortium (pl. consortia) a group of different species of microorganisms 

that act together as a community. 

Conspecific belonging to the same species. 

Coprophagy the act of feeding on excrement. 

Corpora allata a pair of small glandular structures, located 

immediately behind the brain, that produce juvenile hormone. 

Coxa (pl. coxae) the basal segment of the leg. 

Crepuscular active during twilight hours, dusk, and/or 

dawn. 

Cryptic used of coloration and markings that allow an organism 

to blend with its surroundings. 

Cuticle the non-cellular outer layer of the body wall of an 

arthropod. 

Cycloalexy the formation of a rosette-shaped defensive aggregation. 

Dealation wing removal. 

Dehiscence the act of opening or splitting along a line of 

weakness. 

Diapause a dormancy not immediately referable to adverse 

environmental conditions. 

Dimorphism pertaining to a population or taxon having 

two, genetically determined, discontinuous morphological 

types. Sexual dimorphism: differing morphology between 

the males and females of a species. 

Dipterocarp tree of the family Dipterocarpaceae. 

Elytron (pl. elytra) a thickened, leathery, or horny front 

wing. 

Embryogenesis the development of an embryo. 

Emmet an ant (archaic). 

Encapsulation the act of enclosing in a capsule. 

Endemic native to, and restricted to, a particular geographic 

region. 

Endophallus the inner eversible lining of the male intromittent 

organ. 

Endosymbiont symbiosis in which one symbiont (the endosymbiont) 

lives within the body of the other. 

Epigean living above the soil surface. 

Epiphyll an epiphyte growing on a leaf. 

Epiphyte an organism growing on the surface of a plant. 

Euplanta(e) a swelling on a tarsal segment that facilitates adhesion 

to the substrate during locomotion. 

Eusociality the condition where members of a social group 

are integrated and cooperate in taking care of the young, 

with non-reproductive individuals assisting those that 

produce offspring, and with an overlap of different generations 

contributing to colony labor. 

Exuvium (pl. exuvia) the cast skin of an arthropod. 

Fossorial adapted for or used in burrowing or digging. 

Fungistatic referring to the inhibition of fungal growth. 

Geophagy the act of feeding on soil. 

Gestation the period of development of an embryo, from 

conception to hatch or birth. 

Gonopore the external opening of a reproductive organ. 

Gravid carrying eggs or young; pregnant. 

Gregarious tending to assemble actively into groups or clusters. 

Guild a group of species having similar ecological resource 

requirements and foraging strategies. 

Gynandromorphs individuals of mixed sex, having some 

parts male and some parts female. 

Hemimetabolous a pattern of development characterized by 

gradual changes, without distinct separation into larval, 

pupal, and adult stages. 

Hemocyte a blood cell. 

Heterochrony an evolutionary change in the onset or timing 

of the development of a feature relative to the appearance 

or rate of development of the same feature during the ontogeny 

of an ancestor. 

Heteroploidy an organism or cell having a chromosome 

number that is not an even multiple of the haploid chromosome 

number for that species. 

Heterotrophic used of organisms unable to synthesize organic 

compounds from inorganic substrates. 

Heterozygosity the condition of having two different alleles 

at a given locus of a chromosome pair. 

Holometabolous complete metamorphosis, having welldefined 

larval, pupal, and adult stages. 

Homoplasy resemblance due to parallelism or convergent 

evolution rather than common ancestry. 

Hyaline transparent, colorless. 

Hypogean living underground. 

Hypopharyngeal bladders a specialization of the mouthparts 

in some desert cockroaches that allows them to utilize atmospheric 

water. 

Hypoxia oxygen deficiency. 

Imago the adult stage of an insect. 

Inquiline a species that lives within the burrow, nest, or 

domicile of another species. 

Intercoxal referring to the area between the coxae, or basal 

portion of the legs. 

Intromittent referring to something that allows, permits, or 

forces entry. 

Iteroparous having repeated reproductive cycles. 

Keel the raised crest running along the dorsal midline of an 

ootheca. 

Macropterous tegmina and/or wings that are fully developed 

or only slightly shortened. 

Mallee a thicket of dwarf, multi-stemmed Australian eucalypts. 

Mechanoreceptor a sensory receptor that responds to mechanical 

pressure or distortion. 

Metanotum the third dorsal division of the thorax. 

Metathoracic referring to the third segment of the thorax. 

180 GLOSSARY

Methanogens methane-producing bacteria. 

Mimicry the close resemblance of one organism (the mimic) 

to another (the model) in order to deceive a third organism. 

Monandrous (n. monandry) used of a female that mates with 

a single male. 

Monophyletic referring to a group, including a common ancestor 

and all its descendents, derived from a single ancestral 

form. 

Morphotype a collection of characteristics that determine 

the distinct physical appearance of an organism. 

Mycetocyte a cell of the fat body specialized for housing bacterial 

symbionts. 

Mycorrhiza(e) the symbiotic association of beneficial fungi 

with the small roots of some plants. 

Myrmecophile an organism that spends part or all of its lifecycle 

inside of an ant nest. 

Natal pertaining to birth. 

Necrophagy feeding on corpses. 

Neonates newborns. 

Nuptial referring to the act or time of mating. 

Ommatidium (pl. ommatidia) a single unit or visual section 

of a compound eye. 

Omnivore (adj. omnivorous) feeding on a mixed diet of plant 

and animal material. 

Ontogeny (adj. ontogenetic) the course of growth and development 

of an individual. 

Oocyte a cell that produces eggs (ova) by meiotic division. 

Oogenesis the formation, development, and maturation of 

female gametes. 

Oviparity (adj. oviparous) producing an ootheca that is deposited 

in the external environment. 

Ovoviviparity (adj. ovoviviparous) producing an ootheca 

that is withdrawn into the body and incubated in a brood 

sac; eggs have sufficient yolk to complete embryonic development. 

Typically, eggs hatch as the ootheca is expelled 

and active nymphs emerge. 

Paedomorphosis retention of the juvenile characters of ancestral 

forms by the adults, or later ontogenetic stages, of 

their descendents. 

Palp(s) a segmented, sensory appendage of the mouthparts. 

Paraglossa(e) one of a pair of lobes at the tip of the “lower 

lip” (labium). 

Paraphyletic a taxonomic group that does not include all the 

descendents of a common ancestor. 

Paraproct(s) one of a pair of lobes bordering the anus. 

Parthenogenesis the development of an individual from a female 

gamete that is not fertilized by a male gamete. 

Phagocytosis the ingestion of solid particulate matter by a 

cell. 

Phagostimulant anything that triggers feeding behavior. 

Phallomere(s) sclerites of the male genitalia. 

Phenology timing of the stages of the lifecycle, and its relation 

to weather and climate. 

Phoresy (adj. phoretic) a symbiosis in which one organism is 

transported on the body of an individual of a different 

species. 

Phylloplane the leaf surface, including the plants, algae, 

fungi, etc. associated with it. 

Polyandrous (n. polyandry) used of a female that mates with 

more than one male. 

Polyphenism the condition of having discontinuous phenotypes 

that lack genetic fixation. 

Proctodeal referring to the hindgut. 

Pronotum the first dorsal division of the thorax. 

Protibiae the tibiae of the first set of legs. 

Proventriculus the gizzard. 

Pseudopenis an intromittent type male genital appendage 

that does not function to transfer sperm. 

Pterothoracic referring to the wing-bearing segments of the 

thorax. 

Quiescence a resting phase that occurs in direct response to 

deleterious physical conditions; it is terminated when conditions 

improve. 

Rhizosphere the zone surrounding plant roots. 

Sclerite a hardened plate of the exoskeleton bounded by sutures 

or membranous areas. 

Sclerotized hardened. 

Semelparous a life history where an organism reproduces 

just once in its lifetime. 

Semi-voltine used of taxa that require 2 yr to develop to the 

adult stage of the lifecycle. 

Seta(e) a bristle. 

Spermatheca a receptacle for sperm storage in females. 

Spermatophore a capsule containing sperm that is transferred 

from the male to the female during copulation. 

Spiracle an external opening of the tracheal system; breathing 

pore. 

Stadium the period between molts in a developing arthropod. 

Sternal gland a gland on the ventral surface of the abdomen. 

Stigmatic referring to the stigma, the upper end of the pistil 

in a flower. 

Stomodeal referring to the foregut. 

Subgenital plate a plate-like sclerite that underlies the genitalia. 

Subsocial the condition in which one or both parents care 

for their own young. 

Tarsus (pl. tarsi) the leg segment distally adjacent to the 

tibia; may be subdivided into segments (tarsomeres). 

Taxon (pl. taxa) any group of organisms, populations, or 

taxonomic groups considered to be sufficiently distinct 

from other such groups as to be treated as a separate unit. 

Tegmen (pl. tegmina) the thickened or leathery front wing of 

cockroaches and other orthopteroid insects. 

Teneral a term applied to a recently molted, pale, soft-bodied 

arthropod. 

Tergal glands glands on the dorsal surface of the abdomen; 

usually referring to those on males that entice females into 

position for copulatory engagement. 

Tergite a sclerite of the dorsal surface of the abdomen. 

Termitophile an organism that spends part or all of its lifecycle 

inside of a termite nest. 

Thigmotaxis (adj. thigmotactic) a directed response of a 

motile organism to continuous contact with a solid surface. 

Thorax the body region, located behind the head, which 

bears the legs and wings. 

GLOSSARY 181

Tibia (pl. tibiae) the fourth segment of the leg, between the 

femur and the tarsus. 

Trachea(e) a tube of the respiratory system. 

Transovarial transmission the transmission of microorganisms 

between generations of hosts via the eggs. 

Trichomes hair-like structures found on plant epidermis. 

Troglomorphic having the distinct physical characteristics of 

an organism adapted to subterranean life. 

Trophallaxis mutual or unilateral exchange of food between 

individuals. 

Univoltine having one brood or generation per year. 

Uric acid end product of nitrogen metabolism. 

Uricolytic capable of breaking down uric acid. 

Uricose glands male accessory glands that store and excrete 

uric acid. 

Urocyte a cell in the fat body specialized for the storage of 

uric acid. 

Vitellogenin yolk protein. 

Viviparity (adj. viviparous) producing an ootheca that is 

withdrawn into the body and incubated in a brood sac. 

Eggs lack sufficient yolk to complete development, embryos 

rely on secretions from the brood sac walls for 

nourishment. Active nymphs emerge from the female. 

Volant capable of flying. 

182 GLOSSARY

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Index 

accessory glands: female, 44; 

male, 73, 89, 94, 110. See 

also uric acid, uricose 

glands 

activity rhythms, 39–41, 49, 

54, 61, 62, 140, 141. See 

also seasonality 

aggregation(s), 79, 132–41, 

145, 149, 152, 153, 157, 

160, 163, 169, 172; cost of, 

137, 141; and disease 

transmission, 87; environmental 

influences, 136, 

137; formation of, 86; as 

nurseries, 140–41; relatedness 

in, 133–34; size and 

composition, 134–35. See 

also pheromones 

aggression, 3, 63, 71, 135, 

140, 141, 151, 163, 175; 

during courtship, 106; 

male-male, 90, 102, 134; 

maternal, 127, 132, 142, 

145; in termites, 156 

aging, 19, 106, 122 

Aglaopteryx, 59, 133 

Agmoblatta, 113 

Allacta, 20, 37, 102 

Alloblatta, 50 

allometry, 3, 6, 9, 10, 123 

Alluaudellina, 14, 52, 54, 157 

Amazonina, 100 

American cockroaches. See 

Periplaneta americana 

amoebae, 76, 77, 87 

Anamesia, 47, 167 

Anaplecta, xii, 24, 111, 112 

Anaplectinae, xii, xiii, 25, 53, 

97, 124 

Anaplextinae, 5 

Anastatus, 127 

Ancaudellia, 31, 32, 49 

Angustonicus, 30 

Anisogamia, 8, 40, 44, 167 

antibiotics, 82, 78, 87, 172 

ants, 5, 58, 69, 71, 166; 

Acromyrmex, 50; Atta, 29, 

50; Campanotus, 29, 50; 

Crematogaster, 28, 39, 50; 

Dorylus, 50; Formica, 29; 

as hosts, 20, 28–29, 39, 

50–51, 83, 153, 156; Pogonomyrmex, 

11; as predators, 

11, 127, 128, 132, 138, 

142, 145; Pseudomyrmex, 

50; Solenopsis, 29, 50 

Apotrogia, 41, 134 

Aptera, 142 

aquatic cockroaches, 57–58. 

See also rafting; swimming 

Archaea, 159, 172 

Archiblatta, xii 

Archiblattinae, xii 

Archimandrita, 6, 97 

Arenivaga, 22–23, 32, 38, 50, 

51, 54 – 56, 62, 68, 70, 94, 

134, 154; morphology, 5, 

12, 20, 23, 36; as prey, 

170; spermatheca, 111– 

13 

Aspiduchus, 52, 173 

asymmetry, 2, 101 

Attaphila, 6, 7, 13–14, 35, 50, 

51, 126, 153, 156; phoresy, 

28–29; size, 7 

Australian burrowing cockroaches. 

See Geoscapheini 

Austropolyphaga, 47 

bacteria, 69, 70, 76–83, 86– 

88, 158–61, 166–67, 169, 

171; in caves, 75; in soil, 

172. See also bacteroids; 

hindgut microbiota; 

methanogens; pathogens 

bacteroids, 73, 74, 83–88, 

100, 147, 151, 160–61, 175; 

phylogeny of, 83–84; 

transmission of, 83 

Balta, 4, 27, 68 

Bantua, 3, 12 

bats, 15, 40, 41, 52, 74, 77, 

139, 171. See also guano 

beetles, 1, 3, 12, 33, 46, 48, 74, 

75, 104, 137, 145, 172; 

Lampyridae, 5; mimicry 

of, 4–5, 7, 24, 25, 58, 128; 

Monolepta, 5; Oides, 5 

Beybienkoa, 69 

bioluminescence, 91 

biomass, 54, 59, 166–67, 169, 

170, 172 

birds, 133, 139, 163; droppings/guano, 

35, 69, 74, 

78–79, 85, 86, 99, 101, 118, 

149, 158; nest as habitat, 

29, 37, 51, 58, 59, 77, 119, 

132, 166, 172; as predators, 

50, 128, 171 

Blaberidae, xii, xiii, 12, 64, 90, 

92, 93, 96, 99, 101, 106, 

108, 109, 111–13, 119, 123, 

124–26, 130, 140, 142 

Blaberinae, xii, 10, 94 

Blaberus craniifer, 33, 41, 72, 

84, 87, 94, 108, 110, 122, 

130, 134; aggregation, 136; 

aggression, 102; brooding, 

142; burrowing, 23; in 

caves, 52; copulation, 106; 

flight, 26; pronotum, 3, 4; 

size, 6, 8; spermathecae, 

113 

Blaberus (genus and other 

species), xii, 5, 6, 21, 26, 

33, 46, 47, 52, 78, 88, 97, 

106, 117, 123, 129–30, 134, 

136, 146; in caves, 39, 41, 

225

Blaberus (continued) 

51, 74; locomotion, 18, 19; 

pheromones, 138, 140 

Blaptica, xii, 10, 35 

Blatta, 8, 20, 26, 27, 42, 52, 

57, 67, 72, 96, 101, 108, 

121, 140, 172; aggregation, 

133; building behavior, 

154; ootheca, 117–18, 121, 

129 

Blattabacterium. See bacteroids 

Blattella germanica, xi, 2, 7, 

18, 19, 20, 38, 57, 70, 72, 

84, 121, 153, 156; activity 

cycle, 40; aggregation, 

131–41; autotilly, 156; cannibalism, 

71; in caves, 52; 

coprophagy, 79; courtship/ 

copulation, 90, 99, 101, 

106, 107, 110; flight, 26; 

foraging, 62–65, 76; genitalia, 

101–3; gestation, 

110; migration, 33; nuptial 

gifts, 100–101; ootheca, 

117–19, 123–28; sanitary 

behavior, 87; size, 8–10; 

sperm, 94–95; spermathecae, 

113–15; spermatophore, 

94, 108; starvation, 

67, 122; tergal gland, 

98–99; uric acid, 99– 

101 

Blattella (genus and other 

species), 15, 50, 52, 71, 74, 

75, 93, 98, 100, 114, 119, 

127–29, 132, 139; asahinai, 

19, 26, 39, 46, 68, 71, 90, 

174; vaga, 26, 65, 67, 71, 

77, 121, 122, 128, 143, 146 

Blattellidae, xii, xiii, 7, 16, 18, 

54, 62, 64, 80, 84, 91, 94, 

96, 98, 103, 108, 111, 114– 

15, 123, 124–26, 153, 169, 

170, 174 

Blattellinae, xii, 84, 94, 99, 

101, 102, 104, 111–12, 114, 

119, 124–25 

Blattidae, xii, xiii, 106, 123, 

153 

bromeliads. See epiphytes 

brood sac, 65, 91, 108–10, 

116, 119–21, 123–26, 

128–30, 146–48 

burrowing/building, 9, 20, 

45–50, 55, 105, 153–55; 

ecological impact of, 165– 

68; head raising, 3, 23; 

sand swimming, 22–23; 

scratch digging, 21–22; 

tooth digging, 22; and 

wing loss, 34 

Byrsotria, 2, 96, 97, 102, 104, 

106, 108, 109, 119, 120–23, 

130, 136, 142, 146, 153 

Caeparia, 30, 31, 32 

calcium oxalate, 125–26 

calling, 91, 106, 107, 140 

Calolampra, 46, 68, 70, 125, 

172 

cannibalism, 71–73, 83, 87, 

117, 126–27, 130, 140–42, 

147, 151, 153, 157, 158, 

161, 175 

canopy cockroaches, 4, 7, 25, 

28, 29, 34, 37, 42, 44, 45, 

50, 58–60, 62, 68, 69, 93, 

166, 169, 170; dominance 

of habitat, xii, 58, 169. See 

also epiphytes; soil, suspended 

Capucina, 4, 10, 11, 38, 62, 

65, 66, 69 

Cardacopsis, 5, 24 

Cardacus, 24 

Cariblatta, 18, 38, 41, 55, 58, 

65, 66, 68, 69, 100, 133 

carnivory, 70–73; in caves, 

74–75; predation, 71, 151, 

171 

Cartoblatta, 123, 138 

cave cockroaches, 6, 7, 9, 27, 

34–36, 41–42, 44–46, 51– 

54, 71, 127, 131–34, 138, 

139, 154, 172–74; diet, 61, 

70, 73–75; morphology, 5, 

14–16, 20, 28, 29–30; 

oothecae of, 54; as prey, 

171; zonation, 39, 52–53 

Celatoblatta, 27, 37, 42, 43, 

173 

cellulase, 77–78, 151, 159, 

165 

cellulose, 77–79, 81, 159 

chitinase, 73, 83 

Chorisia, 119 

Chorisoneura, 24, 28, 34, 51, 

58, 133 

Chorisoserrata, 104 

Choristima, 24 

Chromatonotus, 43 

Coelophora, 5 

Colapteroblatta 2, 7, 12, 48 

cold tolerance, 37, 42–43, 86, 

173 

Coleoptera. See beetles 

coloration, 2, 4–6, 16, 36, 58, 

91, 118; aposematic, 4, 138, 

142; cryptic, 4, 118, 128, 

130; lack of, 5; of musculature, 

25–26; of oothecae, 

125–26; of wings, 24, 31– 

32 

communication, 3–4, 14, 19, 

41; acoustic, 92–93, 137, 

152–53. See also pheromones. 

competition, 10, 141, 156, 

173; for food, 62–63, 72, 

121, 138, 147, 148, 174; for 

mates, 3, 8, 89, 96, 101–2, 

105, 134. See also aggression; 

sperm, competition 

Compsagis, 12, 13, 48 

Compsodes, 29 

Comptolampra, 20 

conservation, 173–74 

conspecific food, 64, 71–73, 

141, 149, 152, 158; evolution 

of secretions, 129 

coprophagy, 51, 64, 73, 77, 

78–80, 85–87, 142, 157, 

158, 160, 161, 163, 172. See 

also feces; guano 

copulation. See mating 

courtship, 27, 73, 91–93, 96, 

98–99; copulatory, 103–5; 

female response to, 106–7 

crevice fauna, 10, 32, 34, 44– 

46, 132, 134, 137. See also 

harborage 

Cryptocercidae, xii, xiii, 5, 12, 

22, 46, 48, 97, 105, 142, 

145, 150–51, 154; as 

decomposers, 166–67 

Cryptocercus, xii, 10, 12, 20, 

26, 43, 44, 48, 49, 70, 81– 

82, 84, 86, 105, 169; allogrooming, 

73; altricial 

development, 5, 147; bacteroids, 

83; burrowing/ 

building, 3, 22, 154–55; 

cannibalism, 72, 130; 

cold hardiness, 43, 86; coprophagy, 

80; copulation, 

90, 97, 105; dispersal, 33; 

ecology, 171–74; paedomorphosis, 

35–36; oothecae, 

72, 118, 123; parental 

care, 129, 145–48; as prey, 

170; pronotum, 3; sanitary 

behavior, 87, 154; size, 7, 8; 

spermathecae, 111–12; in 

relation to termites, 150– 

63; trophallaxis, 80 

cuticular hydrocarbons, 51, 

135, 153 

Cyrtotria, 2, 3, 12, 32, 49 

defensive behavior, 11, 14; 

in aggregations, 137–38; 

chemical defenses, 4, 11, 

87, 128, 130, 138, 172; 

parental, 145, 146, 161 

Dendroblatta, 100, 133, 138 

Derocalymma, 43 

Deropeltis, xii, 46 

desert cockroaches, 28, 54– 

57; ecological impact, 167– 

69; as prey, 170; wing loss 

in, 34. See also Polyphagidae 

Desmozosteria, 142, 167 

detritus. See plant litter 

development, 10, 44, 81, 86, 

88, 139, 141, 155–58, 161– 

64; altricial, 5, 147, 164; 

arrested, 155, 156; control 

of, 155–57; embryonic, 

120–21, 129; injury and, 

156; nutrition and, 85, 156; 

precocial, 123. See also 

group effects; heterochrony; 

life history 

diapause, 43–44 

diet, 10, 40, 57, 61–75; 

aquatic cockroaches, 57; 

cave cockroaches, 73–75; 

inquilines, 50; mixing, 63; 

quantity, 66, 167; sexual 

differences, 64–65; and 

social behavior, 149, 158, 

164. See also guano; microbivory; 

wood feeding 

digestive tract: crop, 66; 

hindgut, 66, 77, 86, 166; 

proventriculus, 70, 82. See 

also hindgut microbiota 

Diploptera, 11, 19, 24–26, 71, 

91, 94, 113, 140; copulation, 

105–8, 110; courtship, 

93; development, 8– 

10, 163; foraging, 62, 64, 

65, 68; group size, 134; 

sperm competition, 95– 

96; starvation, 67; viviparity, 

73, 119–23, 125, 128– 

30 

Diplopterinae, 25, 94, 125 

disease. See pathogens 

dispersal, 27, 32, 33, 34, 45, 

46, 141, 153, 173. See also 

migration 

distribution, 35, 39, 44, 49, 

122, 132, 169, 170; relation 

to diet, 36, 48, 53, 63; vertical 

stratification, 41–42, 

54–55, 60, 62. See also 

plant associations 

Dryadoblatta, 57 

Ectobiinae, 25, 111–12, 124 

Ectobius 3, 4, 7, 28, 30, 33, 39, 

40, 42, 68, 113, 121, 134, 

166, 170, 171, 173; lifecycle, 

43–44; oothecae, 

117–18, 123 

226 INDEX

Ellipsidion, 4, 41, 68, 83, 90, 

102, 118 

Elliptorhina, 3, 12, 93 

endangered species, 49, 171, 

173 

Epilampra, 24, 39–42, 51, 57, 

58, 65, 66, 69, 70, 92, 166 

Epilamprinae, xii, 57, 96, 99, 

143 

epiphylls, 40, 62, 65, 69, 71 

epiphytes, 18, 28, 29, 37, 45, 

50, 52, 57–60, 166; 

bromeliads, 29, 38, 57, 58, 

60, 91, 166 

Eremoblatta, 22 

Ergaula, xii, 46, 50 

Escala, 2, 32, 39 

Eubacteria, 159 

Eublaberus, 33, 39, 41, 46, 51– 

53, 66, 72, 74, 87–88, 90, 

108, 121, 122, 127; aggregation, 

133–34, 136, 141; 

building behavior, 154; 

copulation, 105, 106; 

courtship, 93 

Eucarya, 159 

Eucorydia, 4 

Eumethana, 52 

Euphyllodromia, xii, 40, 84 

Eupolyphaga, 37 

Eurycotis, xii, 8, 26, 38, 60, 66, 

67, 98, 106, 133, 138, 140; 

ootheca, 117–18, 127 

eusociality: evolution of, 148, 

151–64; trophic shift 

model, 161–63 

Euthlastoblatta, 51, 54 

Euzosteria, 153 

exocrine glands, 87–88; 

defensive tergal glands, 

72–73, 138; male tergal 

glands, 2, 16, 27, 73, 92, 

96–99, 106, 107, 115, 129 

external rumen, 81 

exuvia, as food, 69, 72–73, 

83, 139, 158 

fat body endosymbionts. See 

bacteroids 

feces/fecal pellets, 76; attractants 

in, 135–36, 139, 141, 

153; as building material, 

3, 22, 153–55, 157; ecological 

impact of, 166–67, 

169–72; size, 7. See also 

coprophagy 

fecundity, 8, 31, 35, 122, 126, 

128–29, 175 

fire ecology, 173–74 

flight. See wings and flight 

foraging behavior, 61–65, 

138–39, 145; in burrowers, 

62–63; cyclical, 64–66, 

128; on leaves, 68–69; 

ontogeny of,63–64 

fossils, xii, 2, 4, 6, 7, 33, 150, 

151 

fungi, 42, 48, 61, 69, 70, 75– 

77, 79, 81–83, 87, 88, 165, 

166, 167, 169; cultured by 

social insects, 28, 50, 83; 

mycorrhizae, 82, 168; 

nitrogen content, 81; as 

pathogens, 87, 88, 155, 

172 

genitalia, male, 16, 89, 101–5, 

110; male-female coevolution, 

114–15 

Geoscapheini, 3, 7, 9, 21–22, 

30, 31, 33, 46, 49, 70, 126, 

173; courtship, 93; distribution, 

49, 54; ecological 

impact, 167–68; evolution 

of, 49; foraging, 62; genitalia, 

105; life history, 49; 

migration, 33; morphology, 

2; parental care, 145 

Geoscapheus, 22, 31, 32, 49, 

70, 78, 117, 120, 167 

German cockroach. See Blattella 

germanica 

gestation, 40, 109–10, 116, 

119–21, 123, 124, 126, 129, 

130, 147; length of, 110, 

128, 148 

global warming, 173 

Griffiniella, 51 

Gromphadorhina, 2, 3, 19, 21, 

46, 49, 57, 72, 88, 92, 96, 

109, 129, 137; copulation, 

102; courtship, 93; parental 

feeding, 119–20, 130, 

131, 142–43, 146, 147; size, 

7–9 

grooming, 73, 81–82, 87, 

152, 157, 158, 163 

group effects, 9, 132, 137, 

140, 141, 145; and reproduction, 

96, 123, 140; in 

relation to termites, 155, 

156–57, 158, 163 

guano, 15, 21, 23, 35, 39, 45– 

46, 53, 54, 64, 71, 73–75, 

134, 138, 153–54, 166, 171, 

173 

Gyna, 38, 41, 50, 53, 58, 74, 

123, 134 

gynandromorphs, 2 

Haanina, 27 

habitat(s), 20, 33, 37–60, 76; 

conservation of, 173–74; 

impact in, 166–70; stratification, 

134; and wing loss, 

27–29, 34–35 

harborage, 38–40, 42, 43, 62, 

63, 131–41, 153 

hatch, 43, 44, 47, 48, 116–17, 

119, 121, 122, 124, 128, 

134, 140, 142; asynchrony 

of, 72, 147, 161 

Hebardina, 28, 33, 74 

Hemithyrsocera, 102 

herbivory, 66–69; in caves, 

74; cryptic, 69, 170; leaf 

foraging, 68–69; nectar, 

62, 68, 170; pollen, 68–69, 

82, 170 

heterochrony, 150, 152, 157– 

58, 163–64; paedomorphosis, 

35–36, 105, 150, 

157, 163–64 

Heterogamia, 167 

Heterogamisca, 56, 70 

Heterogamodes, 46 

hindgut microbiota, 66, 68, 

77–78, 149, 151, 158–60, 

168–69, 171–72; transmission 

to juveniles, 78–80, 

87, 141, 160. See also protozoa 

Holocampsa, 28 

Homalopteryx, 10, 142 

Homoeogamia, 33 

Homopteroidea, 102 

hygiene. See sanitary behavior 

Hymenoptera, 5, 51, 58, 152, 

155; bees, 170; Melipona, 

51; Polybia, 51; Vespula, 51, 

172. See also ants; parasites, 

wasp 

Hypercompsa, 113 

hypopharyngeal bladders. See 

water balance 

Hyporichnoda, 41 

Imblattella, 18, 41, 58, 66, 69, 

84 

immunology, 86, 88, 141 

investment: in immune system, 

88, 141; male, 98– 

101, 145; nitrogenous, 72, 

157; parental, 85, 115, 122, 

123, 129–30, 147–48, 163 

Ischnoptera, 4, 14, 24, 28, 38, 

41, 42, 84, 98 

Isoptera. See termites 

Jagrehnia, 92, 106 

juveniles, 38–40, 45, 75, 81, 

140, 143, 149, 153, 155–58, 

163; aggregation of, 132, 

134, 157; color, 4; difficulty 

in identifying, 1–2, 58; foraging, 

62, 80, 141, 158; 

mortality factors, 43, 140– 

42, 147–48; nutritional 

requirements, 63–64, 78, 

139, 146 

kin recognition, 135, 142, 

152, 153, 157, 163 

laboratory selection, 26, 35, 

141, 175 

Lamproblatta, xii, xiii, 40, 47, 

82, 111–12, 132 

Lanxoblatta, 10, 133 

Latiblattella, 27, 39, 60, 64, 

66, 68, 100, 102, 170 

Lauraesilpha, xii, 30, 47 

Laxta, 2, 4, 7, 10, 28, 32, 36, 

47 

learning, 63, 139–41, 172 

Leiopteroblatta, 13 

Leptozosteria, 10 

Leucophaea. See Rhyparobia 

life history, 85, 175; and 

eusociality, 164; and seasonality, 

43–44; of soil 

burrowers, 49; tradeoffs, 

35, 88; of wood feeders, 

48, 161 

Litopeltis, 47, 57, 70 

Loboptera, 52, 54, 104, 113– 

15, 118 

Lobopterella, 28 

locomotion (terrestrial): 

adhesion to substrate, 

19–21, 28, 68, 143, 145; 

bipedal, 18; climbing, 19– 

21; during gestation, 126, 

128; hindrance by offspring, 

148; during mating, 

102; speed, 17–18; 

stability, 18–19, 27 

Lophoblatta, 100, 104, 117, 

119, 124–26, 129–30 

Lucihormetica, 91 

Macropanesthia rhinoceros, 

19, 21–22, 32, 36, 49, 70; 

burrows, 21, 168; ecological 

impact, 167–68, 172; 

foraging, 40; genitalia, 105; 

mating, 92; pronotum, 3, 

6; size, 6–7, 9 

Macropanesthi (genus and 

other species), 6, 7, 12, 25, 

31, 49, 72, 105, 117, 120, 

129, 145, 147, 167 

Macrophyllodromia, 58, 71 

mantids, 14, 84, 150–52 

Margattea, 44, 46, 170 

Mastotermes, 83, 84, 86, 105, 

126, 151, 161–62 

INDEX 227

Mastotermitidae, xii, 151, 161 

mate choice, 86, 91, 98–99; 

cryptic, 101, 104–5, 114 

mate finding, 64, 91, 139–40 

mating, 101–5; behavioral 

sequence, 92–93; female 

control of, 106–7; frequency, 

90–91; length of, 

90, 93; secondary effects 

of, 110–11, 122–23; type I, 

92, 101; type II, 92; type 

III, 92, 105 

mating system, 89–91; 

monandry, 90, 96, 105; 

monogamy, 90, 105, 108, 

164; polyandry, 90, 96 

Mediastinia, 46 

medicine, cockroach as, 172 

Megaloblatta, 6, 58, 62 

Metanocticola, 53, 96 

Methana, 30, 47, 118 

methanogens, 77, 158; 

methane production, 78, 

171–72 

microbivory, 64, 70, 75–83, 86 

Microdina, 3, 31 

migration, 9, 33, 34, 42, 54, 

62, 127, 133, 134, 137, 175. 

See also dispersal 

mimicry, 4, 27, 51, 88, 98, 

110. See also beetles, mimicry 

of 

Miopanesthia, 30–32 

Miriamrothschildia, 59, 100, 

113, 170 

Miroblatta, 6 

Molytria, 46 

Monastria, 4, 10 

montane cockroaches, 28, 36, 

37, 43, 48, 169–71 

morphology, 1–4, 17, 20–21, 

81; of borers, 12; of burrowers, 

5–6, 12, 22–23; of 

cave cockroaches, 13–14, 

52; of conglobulators, 11– 

12; of desert cockroaches, 

12–13; flattened, 10–11; 

of juveniles, 1–2, 25; of 

myrmecophiles and termitophiles, 

13–14. See also 

pronotum; sexual dimorphism; 

wings and flight 

mymecophiles, 7, 13–14, 28– 

29, 35, 50, 51, 153, 156. See 

also nests 

Myrmecoblatta, 7, 13–14, 28, 

50 

Nahublattella, xii, 58, 66, 84, 

104 

Nauphoeta cinerea, xii, 51, 71, 

122; activity cycle, 40; aggregation, 

133, 140; brooding, 

142; copulation, 94, 

102, 104; courtship, 91, 93, 

106–7; fighting 3; flight, 

26; ovoviviparity, 117, 

119–21, 128; parthenogenesis, 

121; pheromones, 

91, 140; receptivity, 106– 

10; sperm, 94, 96; starvation, 

66–67; stridulation/ 

vibration,3–4,93 

Nelipophygus, 14 

Neoblattella, 113 

Neogeoscapheus, 31, 32, 49, 120 

Neolaxta, 2, 27 

Neoloboptera, 104 

Neopolyphaga, 90 

Neostylopyga, 20, 26, 28, 52, 

66, 67, 106 

Neotemnopteryx, 20, 33, 52, 96 

Neotrogloblattella, 14, 52, 75 

Nesomylacris, 29, 39, 40, 41, 66 

nests, 37, 45, 58, 77, 153–55, 

172; parental care in, 145, 

146, 148; of social insects, 

7, 11, 27, 28–29, 34, 35, 38, 

39, 50–51, 83, 126; of vertebrates, 

54–55, 134. See 

also birds, nest as habitat; 

mymecophiles; termitophiles 

nitrogen, 65, 68, 72, 73, 80, 

81, 122, 139, 147–49, 157– 

58, 163, 164, 166–67; fixation, 

159, 171; from urates, 

63, 83–86, 99–101, 161 

Nocticola, 42, 50, 52–54, 75, 

126, 173; morphology, 7, 

13, 14–16, 24, 28, 35, 157 

Nocticolidae, xii, 14, 16, 52, 

126 

Nondewittea, 104 

nuptial gifts, 8, 73, 86, 95, 

99–101, 115 

nurseries, 21, 38, 40, 87, 140– 

41, 155 

nutrient limitation, 15, 35, 

85. See also starvation 

Nyctibora, xii, 20, 50, 58, 

111–12, 114, 118, 127, 133 

Nyctiborinae, xii, 111, 124 

Nyctotherus, 77–78; phylogeny 

of, 80 

omnivory, 61, 63, 78, 81, 139 

Onychostylus. See Miriamrothschildia 

oogenesis, 64, 110, 125, 163; 

dependence on nutrients, 

122 

oothecae, 116–30, 161, 162, 

172; cannibalism of, 71– 

73; casing, 105, 125–26, 

128; of cave cockroaches, 

54; concealment, 117–18, 

126–27, 153–54; egg 

number, 123; flight while 

carrying, 26, 128; formation 

of, 110; frequency of 

laying, 128; permeability, 

118–19; rotation, 124–25. 

See also hatch 

Opisthoplatia, 20, 24, 44, 57, 

70, 172 

orientation, 19, 50, 135, 142, 

152, 153; in caves, 14; in 

deserts, 23; to sun, 33; 

visual, 91 

Orthoptera, 35, 66–67, 84, 

151 

Oulopteryx, 51 

oviparity, 110, 116–19, 123– 

29; and social behavior, 

141–42, 149 

ovoviviparity, 110, 116–17, 

119–21, 123–130; cost of, 

128–29; and social behavior, 

141–42, 146, 149 

oxygen, 21, 45, 128; hypoxia, 

54–55 

Oxyhaloinae, xii, 93, 94, 96, 

133 

paedomorphosis. See heterochrony 

Pallidionicus, 30 

Panchlora, 4, 47, 62, 92, 123, 

130 

Panchlorinae, 93, 94, 105 

Panesthia, 44, 48–49, 70, 73, 

78, 81, 92, 106, 107, 135, 

158, 167; endangered, 

173; genitalia, 102, 105; 

ootheca, 120; sociality, 105, 

145; wings, 30–33 

Panesthiinae, xiii, 2, 5, 12, 20, 

34, 46, 48, 81, 105, 146; as 

decomposers, 166–67; 

evolution of, 31–32, 49; 

wing development, 30–32 

Paramuzoa, 47 

Parapanesthia, 31, 32, 49, 120 

Parasigmoidella, 102 

parasites, 45, 46, 81, 87, 117, 

127, 137, 158, 171, 172; 

as selection pressure, 126; 

wasp, 50, 71, 126–27, 174 

Parasphaeria, 47 

Paratemnopteryx, 15, 20, 24, 

33, 50–53, 74, 75, 85, 127, 

132; kin recognition, 153; 

morphological variation, 

14, 29, 30, 36 

Paratropes, 58, 68, 111, 170 

Parcoblatta, xii, 4, 8, 26, 38, 

41–43, 51, 59, 63–66, 68, 

70, 71, 82, 91, 96, 102, 105, 

106, 113, 122, 133, 136, 

172; oothecae, 111, 117– 

18, 135; as prey, 171; urate 

excretion, 85–86 

Parellipsidion, 43 

parental care, 5, 11, 48, 123, 

134, 141–49; biparental, 

90, 143, 145, 148, 149; 

brooding, 80, 132, 142, 

148; in burrows 145–46, 

148; cost of, 127–29, 148– 

49, 161–64; feeding, 64, 

73, 80, 120, 129–30, 131, 

142–48, 158, 161; parentoffspring 

conflict, 147–48. 

See also trophallaxis 

parthenogenesis, 121–22 

pathogens, 45, 46, 76, 80, 82, 

87–88, 117, 127, 172, 174; 

sexually transmitted, 88; 

and social behavior, 87, 

137, 141, 147. See also sanitary 

behavior 

Pellucidonicus, 30 

Pelmatosilpha, 51, 118 

perching, 20, 29, 39, 40, 41, 

42, 58, 69, 93, 142, 153 

Periplaneta americana, xi, 2, 

7, 27, 38, 40, 41, 72–73, 78, 

80, 83, 86, 93, 108, 111, 

115, 121, 123, 153, 174–75; 

aggregation, 132–37, 140– 

41, 171; in caves, 52; coprophagy, 

79; copulation, 

90, 102, 107, 110; development, 

155, 157; digging, 

48–49, 154; flight, 25–26, 

35; foraging, 64, 65; genitalia, 

103; as herbivore, 68; 

immunology, 88; learning, 

63; locomotion 17–21; 

ootheca, 117–19, 125–27; 

as predator, 63, 71; as prey, 

171; in sewers, 53; size, 8; 

sperm, 94, 96; starvation, 

65–67, 130, 156; swimming, 

23–24; uric acid, 84; 

water balance, 57 

Periplaneta (genus and other 

species), xii, 8, 20, 26, 38, 

39, 43–44, 50, 57, 63, 66, 

67, 71, 72, 74, 78–79, 84, 

98, 105, 118, 121, 122, 126, 

127, 129, 132–33, 135, 

140, 145, 146, 155, 170, 

172 

Perisphaeria, 11, 33, 43 

Perisphaeriinae, 2, 11, 12, 49, 

144, 146 

228 INDEX

Perisphaerus, 11, 12, 129, 142, 

144, 146–47 

pest cockroaches, 33, 37, 61, 

63, 70–71, 81, 133, 134, 

172, 174; control of, 87, 

141, 171; of plants, 67–68, 

170 

pheromones, 89, 172; aggregation, 

86, 87, 132, 134– 

36, 139–41; alarm, 138; 

dispersal, 141; kairomones, 

126; oviposition, 135; sex, 

35, 42, 91, 93, 97, 106, 107, 

140; trail, 50, 139, 153 

Phlebonotus, 143, 146 

Phoetalia, xii, 51, 125 

Phoraspis, 143 

phoresy, 28–29 

Phortioeca, 10 

Phyllodromica, 57, 97–98, 

122, 132 

phylogeny, 36, 132, 175; bacteroids, 

84; Blattellidae, 

124; Celatoblatta, 27; cockroaches, 

xii, 84; Dictyoptera, 

150–52; Nyctotherus, 

80; Panesthiinae, 31–32, 49 

Pilema, 3, 12, 24, 49 

plant associations, 10, 48, 49, 

54, 68, 167, 169; Acacia, 4, 

20, 32, 49, 50, 68, 167 

plant litter, as food, 49–50, 

62, 64, 65, 69–70, 74, 77, 

80–81, 144, 165–70, 173– 

75. See also wood feeding 

Platyzosteria, 4, 7, 10, 41, 59, 

138 

Plecoptera, 7, 24, 113 

Plecopterinae, xii 

Poeciloblatta, 142 

Poeciloderrhis, 24, 57, 70 

pollination, 170, 174 

Polyphaga, xii, 52, 54, 84, 

111–12, 121, 134 

Polyphagidae xii, xiii, 13, 22– 

23, 24, 32, 36, 54, 92, 96, 

111, 124 

Polyphaginae, xii 

Polyphagoides, 47 

Polyzosteria, 2, 13, 51, 52, 81, 

93, 118 

Polyzosteriinae, xii, 4, 28, 41, 

47, 91, 112 

population(s): gene flow in, 

16, 36, 133; levels, 9, 14, 33, 

48, 53, 71, 131, 134, 141, 

146, 166, 167, 169, 171, 

173–74; microbial, 77, 79; 

variation in, 20, 44 

predation on cockroaches, 4, 

9, 11, 14, 45, 46, 50, 54, 71, 

127, 137–38, 141, 158, 

170–71; evasion of, 25, 

126, 128, 130, 138. See also 

defensive behavior 

Princisia, 3 

pronotum, 2–4, 6, 11, 12, 14, 

22, 23, 91, 93, 157 

Prosoplecta, 4, 5, 24 

protandry, 8 

protein, 63–66, 72–73, 79, 

81–83, 100, 111, 126–28, 

130, 138–39, 146, 156; in 

maternal secretions, 116, 

120, 129; microbial, 64, 81, 

82, 158; in tergal secretions, 

98, 129 

protozoa, 70, 76, 79, 87, 166, 

172; ciliates, 77, 168; flagellates, 

77, 82, 151, 158–60, 

163. See also hindgut 

microbiota; Nyctotherus 

Pseudoanaplectinia, 7, 28, 50, 

51, 119, 125 

Pseudobalta, 119, 125, 130 

Pseudoderopeltis, 46 

Pseudoglomeris, 11, 33, 145 

Pseudomops, 111–13 

Pseudophoraspis, 146, 148 

Pseudophyllodromiinae, xii, 

84, 99, 101, 103, 111–12, 

119, 124–25 

Punctulonicus, 30 

Pycnoscelinae, 94 

Pycnoscelus, 8, 26, 38, 46, 49, 

67, 94, 110, 123, 128, 130, 

140; in caves, 52–53, 74– 

75; copulation, 92; digging, 

49; parthenogenesis, 121– 

22; as prey, 171 

rafting, 27, 28 

refugia, 42, 46, 55 

reproductive mode, 116–17; 

evolution of, 123–29. See 

also oviparity; ovoviviparity; 

viviparity 

respiration, 13, 54, 55, 137, 

142, 157, 172; in gut bacteria, 

159; of methane, 171; 

while running, 21; under 

water, 57–58. See also 

oxygen 

Rhabdoblatta, 57, 169 

Rhyparobia maderae, 51, 57, 

72, 110, 119, 121, 140, 146; 

activity cycles, 40, 41; aggregation, 

133, 153; 

courtship, 93, 106; flight, 

26; foraging, 64, 65; spermathecae, 


108–9; starvation, 

67, 122; tergal gland, 

98, 129 

Rhyparobia (genus and other 

species), 6, 128, 130 

Riatia, 58, 84 

robots, 19, 137 

Robshelfordia, 2, 47 

Rothisilpha, 30 

Salganea, 5, 7, 31–32, 36, 48, 

90, 153; parental care, 

145–48, 158 

sampling, 74, 169, 175; in 

canopy, 58–59; light traps, 

27, 37, 42, 43, 46, 59, 174; 

in pitcher plants, 68; pitfall 

traps, 15, 169, 173; windowpane 

traps, 42 

sanitary behavior, 49, 87, 148, 

152, 154–55, 161, 172. See 

also grooming 

Scabina, 28 

Schizopilia, 133 

Schultesia, 5, 32, 51, 132, 133 

seasonality, 9, 33, 34, 35, 39, 

42–44, 46, 54, 59, 62, 63, 68, 

69, 70, 74, 77, 137, 166, 169 

self organization, 137, 163–64 

semelparity, 148, 162, 164 

sensory trap, 98 

sewers, 26, 33, 42, 45, 52–53, 

76, 78 

sexual dimorphism, 2–3, 7– 

9, 25, 30, 32, 33, 35; and 

starvation resistance, 66 

sexual receptivity, 106–10; 

cyclic, 90; female loss of, 

107–10; male control of, 

100, 105, 108–9; and reproductive 

mode, 110 

Shelfordina, 68, 82 

Simandoa, 46, 75 

size, 6–10, 25, 35, 128, 141, 

167, 172; of eggs, 123; of 

neonates, 120–21; and reproduction, 

123 

Sliferia, 119, 124–26, 129–30 

soil burrowing cockroaches. 

See Geoscapheini 

soil, 165–66; geophagy, 75; 

suspended, 60, 165, 169; 

type, 49 

solitary cockroaches, 132 

Spelaeoblatta, 14, 16, 52 

sperm, 89, 90–91, 98, 100, 

110; choice by females, 86, 

101, 104–5, 111–14; competition, 

90, 95–96, 101; 

influence on reproduction, 

121–22; male-female conflict 

over use, 114–15; manipulation 

by males, 103, 

104, 114–15; morphology, 

94–95; and receptivity, 

107–8; transfer from spermatophore, 

94 

spermathecae, 91, 94–96, 

103–5, 107–8, 110–15; 

multiple, 114; shape, 113– 

14 

spermathecal glands, 94, 108, 

111–13 

spermatophores, 89, 91, 93– 

94, 97, 99–101, 103, 104, 

107–12, 114, 140; ejection, 

108; nutritional value of, 

110–11 

Sphecophila, 51 

spirochetes, 77, 158, 171 

starvation, 8, 15, 64, 65–67, 

74, 78, 82, 85, 86, 99, 120, 

122, 130, 140, 147, 156, 175 

Stayella, 119, 124–25 

stridulation, 3, 93 

subgenual organ, 93, 153 

subsociality. See parental care 

Sundablatta, 47 

Supella, xii, 7, 9, 26, 38, 51, 

63, 87, 103, 121, 128, 139, 

140; copulation, 90; 

courtship, 106; feeding/ 

foraging, 64–65, 152; 

oothecae, 117–18, 135; 

receptivity, 107; size, 8; 

sperm, 94; spermathecae, 


94, 110 

swimming, 23–24, 57, 58 

symbionts. See bacteroids; 

hindgut microbiota 

Symploce, 24, 28, 44, 52, 74, 

85, 128 

taxonomy: characters used 

in, 20, 30, 70, 97, 101, 117, 

124; difficulties in, 4, 32, 

35, 36 

tergal glands. See exocrine 

glands 

termites, xii–xiii, 70, 77, 82, 

88, 105, 126, 148, 175; 

Archotermopsis, 156; Cubitermes, 

156; ecological 

impact, 169, 171–72; evolution/phylogeny, 

84, 150– 

64; Kalotermitidae, xii, 

151; Macrotermes, 50; mating, 

92; Nasutitermes, 50; 

Odontotermes, 28, 50; 

Porotermes, 156; as prey, 

63, 71; Reticulitermes, 86, 

159, 163, 169, 172; Termopsidae, 

xii, 151, 154; 

wings, 31, 157; Zootermopsis, 

155, 156. See also Mastotermes; 

Mastotermitidae 

INDEX 229

termitophiles, 7, 13–14, 28, 

52. See also nests 

Thanatophyllum, 132, 140, 142 

Therea, 45, 84, 90, 92, 117, 

123, 138, 140 

thigmotaxis, 19, 45, 135, 152 

Thorax, 26, 56, 60, 70, 129, 

143, 146, 148 

Tivia, 20, 50 

traps. See sampling 

Trichoblatta, 4, 32, 68, 128, 

145, 146 

Trogloblattella, 7, 16, 52, 53, 

74, 75 

troglomorphy, 14–16, 29, 52, 

53–54 

trophallaxis, 80, 82, 151, 158, 

160, 161, 163, 164 

Tryonicinae, xii, 30 

Tryonicus, xii, 20, 47, 113– 

14 

Typhloblatta, 52 

urates. See uric acid 

uric acid, 63, 66, 71, 80, 83– 

86, 99–101, 161; uricose 

glands, 99–101 

vibration. See communication, 

acoustic; stridulation 

vibrocrypticity, 21 

vitellogenesis. See oogenesis 

viviparity, 64, 116–17, 120– 

21, 123, 125–26, 128–30, 

141, 146; “milk” composition, 

120 

water balance, 9, 11, 12–13, 

28, 43, 54–57, 117–19, 

126, 127, 137, 141; cyclical 

drinking, 65–66; of microorganisms, 

166, 168–69 

wings and flight, 2, 4, 24–36, 

128, 157; in caves, 29; cost 

of, 28; dealation, 30–31; 

ecological correlates, 27– 

29; evolution, 31–34; 

flight-oogenesis syndrome, 

35; folding, 24; nectar as 

fuel, 68; physiology, 25– 

26, 35; reduction, 25–27, 

33–36; variation within 

taxa, 30–33 

Wolbachia, 88 

wood feeding, 46–48, 62, 70, 

166–67; and sociality, 145, 

152. See also cellulase; 

hindgut microbiota; plant 

litter 

Xestoblatta, 40, 41, 51, 52, 65, 

66, 93, 130; spermathecae, 

111–13; uricose glands, 73, 

100 

yeasts, 63, 77, 81 

Ylangella, 47 

Zetoborinae, 94 

Zonioploca, 52 

230 INDEX

Cockroache; Ecology, behavior & history - W.J. Bell

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