Vol. 3: Insects

Order: Plecoptera

Species accounts

Common needlefly

Zealeuctra claasseni

FAMILY

Leuctridae

TAXONOMY

Zealeuctra claasseni (Frison), 1929, Herod, Illinois, United States.

PHYSICAL CHARACTERISTICS

Adults and larvae with typical elongate body of the family Leuctridae; males have a single cercal segment. Larvae are gill-less.

DISTRIBUTION

Midwestern United States.

HABITAT

Small, often intermittent streams.

BEHAVIOR

Nothing is known.

FEEDING ECOLOGY AND DIET

CONSERVATION STATUS

Not threatened. A hardy stonefly, able to survive for several drought years as diapausing eggs in intermittent streams.

SIGNIFICANCE TO HUMANS

None known.

Giant salmonfly

Pteronarcys californica

FAMILY

Pteronarcyidae

TAXONOMY

Pteronarcys californica Newport, 1848, California, United States.

PHYSICAL CHARACTERISTICS

Large (1.18–1.97 in [30–50 mm]), dark brown stoneflies. Larvae have profuse, filamentous thoracic and abdominal gills, retained as stubs in adults.

Herbivore-detritivore.	DISTRIBUTION
REPRODUCTIVE BIOLOGY	Widespread in western North America.

A winter-emerging species (November–February). Males call females on leaf mats and plants with a drumming signal of about 20 beats, and females answer with a similar signal. Drumming and mating occur within a day after emergence, and oviposition follows the same day or a day later.

Hesperoperla pacifica

Zealeuctra claasseni

Pteronarcys californica

HABITAT

Cobble substrates of large streams and rivers.

BEHAVIOR

Adults aggregate on riparian vegetation for drumming and mating.

FEEDING ECOLOGY AND DIET

Major shredders of decomposing leaves in streams.

REPRODUCTIVE BIOLOGY

Males call females on debris and plant substrates with heavy 6- beat signals, and females answer with similar signals. Springemerging species. Larvae require two to three years for development.

CONSERVATION STATUS

Not threatened.

SIGNIFICANCE TO HUMANS

Important stream food web components and major trout food. Very important to fly fishermen, who create artificial fly lure that resembles both adults and larvae.

Golden stone

Hesperoperla pacifica

FAMILY

Perlidae

TAXONOMY

Hesperoperla pacifica (Banks), 1900, Olympia, Washington, United States.

Grzimek’s Animal Life Encyclopedia

145

Order: Plecoptera

PHYSICAL CHARACTERISTICS

Yellow-orange colored stoneflies, 0.71–1.18 in (18–30 mm) body length. Larvae have branched, filamentous gills arising from the ventral thorax and tenth abdominal segment, retained as stubs in adults.

DISTRIBUTION

Widespread in western North America.

HABITAT

Coarse gravel and cobble substrates of small and large streams and rivers.

BEHAVIOR

Adults aggregate on streamside rocks, debris, and vegetation for drumming and mating.

Vol. 3: Insects

FEEDING ECOLOGY AND DIET

An insectivorous predator that feeds mainly on bloodworm (Chironomidae) larvae and mayfly and caddisfly larvae.

REPRODUCTIVE BIOLOGY

Males call females with monophasic, 12-beat drumming signals, females answer with 16-beat signals, then males reply with 22-beat signals. A spring-emerging species. Hatchling larvae require more than one year for development.

CONSERVATION STATUS

Not threatened.

SIGNIFICANCE TO HUMANS

An important trout food insect. Fly fishermen model their lure after it.

Resources

Books

Resh, V. H., and D. M. Rosenberg. The Ecology of Aquatic Insects. New York: Praeger Publishers, 1984.

Sinitschenkova, N. D. “Paleontology of Stoneflies.” In

Ephemeroptera and Plecoptera, edited by Peter Landolt and Michel Sartori. Fribourg, Switzerland: Mauron and Tinguely; Lachat SA, 1995.

Stark, B. P., S. W. Szczytko, and C. R. Nelson. American Stoneflies: A Photographic Guide to the Plecoptera. Columbus, OH: Caddis Press, 1998.

Stewart, K. W. “Vibrational Communication (Drumming) and Mate-searching Behavior of Stoneflies (Plecoptera); Evolutionary Considerations.” In Trends in Research in Ephemeroptera and Plecoptera, edited by Eduardo Dominguez. New York: Kluwer Academic/Plenum Publishers, 2001.

Stewart, K. W., and P. P. Harper. “Plecoptera.” In An Introduction to the Aquatic Insects of North America, 3rd ed., edited by R. W. Merritt and K. W. Cummins. Dubuque, IA: Kendall/Hunt Publishing, 1996.

Stewart, K. W., and B. P. Stark. Nymphs of North American Stonefly Genera (Plecoptera), 2nd ed. Columbus, OH: Caddis Press, 2002.

Periodicals

Shepard, W. D., and K. W. Stewart. “Comparative Study of Nymphal Gills in North American Stonefly (Plecoptera) Genera and a New, Proposed Paradigm of Plecoptera Gill Evolution.” Miscellaneous Publications Entomological Society of America 55 (1983): 1–57.

Stewart, K. W. “Theoretical Considerations of Mate-finding and Other Adult Behaviors of Plecoptera.” Aquatic Insects 16 (1993): 95–104.

—. “Vibrational Communication in Insects: Epidomy in the Language of Stoneflies.” American Entomologist 43 (1997): 81–91.

Zwick, P. “Phylogenetic System and Zoogeography of the Plecoptera.” Annual Review of Entomology 45 (2000): 709–746.

Kenneth W. Stewart, PhD

146	Grzimek’s Animal Life Encyclopedia

●

Blattodea

(Cockroaches)

Class Insecta

Order Blattodea

Number of families ca. 7

Photo: A German roach (Blattella germanica) resting on a leaf in Florida, USA. (Photo by Bob Gossington. Bruce Coleman, Inc. Reproduced by permission.)

Evolution and systematics

Fossil cockroaches or cockroach-like species are so numerous in the coal seams of the Upper Carboniferous (350 million to 400 million years ago [mya]) that the period is known as the “Age of Cockroaches.” Only about 5% of fossil cockroaches represent entire insects; 90% consist of wings or wing fragments, with the remaining 5% consisting of other body parts. For the most part, these fossils appear to be very similar to the forms living today. However, the females of many fossils from the Carboniferous and Permian deposits (270 to 225 mya) of Europe, Asia, and North America, as well as from the Triassic (225 to 180 mya) and Jurassic deposits (135 to 100 mya) of Russia, had long, external ovipositor valves. This indicates that they probably laid single eggs in soil or soft plant tissue, rather than a number of eggs in an ootheca, which is characteristic of today’s forms. During the Jurassic period the ovipositor valves decreased in length and gradually evolved into those found in all present-day species.

The oldest fossil genus in the Blattellidae (one of the largest families), Pinablattella, dates to the Cretaceous (135 mya) of Siberia. The coexistence of fossil cockroaches and fossil plants in the same geological stratum suggests that there was a close association between them during this early period, and it is speculated that the cockroaches fed on these plants. Cockroaches are related closely to termites and mantids, with which they often have been grouped in the order Dictyoptera. This chapter treats cockroaches as comprising the order Blattodea, which does not include termites and mantids. Cockroaches can be divided into two large superfamilies, the Blattoidea and the Blaberoidea. These two groups evolved from oviparous ances-

tors; the Blattoidea remained oviparous, and the Blaberoidea eventually evolved ovoviviparity and viviparity.

Physical characteristics

The chewing mouthparts are directed downward. The antennae consist of numerous segmented annuli and usually are longer than the body. Compound eyes typically are present, but they may be reduced in size or absent, especially in cavernicolous (cave-dwelling) species. The pronotum is large and often shieldlike and covers the head. When present, the forewings typically are modified into hardened tegmina, which may be abbreviated or absent; hind wings may be reduced in size or absent, if present, they are membranous, with well-developed veins. Legs are adapted for running or sometimes digging. The coxae are adpressed against the body. The tarsi have five segments, often with pulvilli, which may be reduced, or absent. Tarsal claws almost always are present, with or without an arolium between them.

Sizes vary widely, the smallest being about 0.8 in (2 mm) long, the size of a mosquito (e.g., Nocticola species). The largest species generally are in the Blaberidae; the wingless Macropanesthia rhinoceros (Panesthiinae) probably is the bulkiest cockroach known, and it may reach 2.6 in (65 mm) in length and weigh 0.53–1.1 oz (15–30 g) or more. Another wingless blaberid, Gromphadorhina portentosa, may reach a length of 3.1 in (80 mm). Some fully winged neotropical blaberids may have a body length of 3 in (75 mm) (Archimandrita tessellata) or 3.1 in (80 mm) (Blaberus giganteus).

Numerous species are uniformly dark (black, brown, or reddish brown), but many are distinctively marked. A large

Grzimek’s Animal Life Encyclopedia

147

Order: Blattodea

An oriental cockroach (Blatta orientalis) cleaning its antennae. (Photo by Adrian Davies. Bruce Coleman, Inc. Reproduced by permission.)

number (especially Panesthiinae) are aposematic (brightly colored as a warning signal to predators), with white or yellow markings that warn potential predators that they are poisonous or dangerous. While many species do indeed secrete distasteful chemical compounds for defense, others may only mimic this adaptation with their coloration.

Distribution

Cockroaches are worldwide in distribution, although some genera are endemic to certain countries. The greatest number of species occurs in the tropics. Some pest species, if not controlled, may build up huge populations in homes, businesses, and other buildings and in sewers.

Habitat

Feral cockroaches inhabit almost every conceivable habitat, with the exception of extremely cold regions, although Eupolyphaga everestinia (Polyphagidae) was collected on Mount Everest at 18,500 ft (5,639 m); pest species (e.g., the German cockroach) can survive indoors in extreme cold. Cockroaches are found in caves, mines, animal burrows, bird nests, ant and termite nests, deserts, and water (subaquatic). Most cockroaches live outdoors and, during the day, usually are found near the ground and hiding under bark, dead leaves, soil, logs, or stones. Numerous species have adapted to human beings and live in man-made structures (homes, restaurants, food stores, hospitals, and sewers) where temperatures and levels of humidity are relatively stable and the cockroaches are protected from adverse climatic conditions.

Many species are found in association with plants, but the significance of the relationships is obscure. Undoubtedly,

Vol. 3: Insects

most of the associations are accidental, but some damage plants. Not all cockroach/plant associations are harmful. There are some tropical species that live in the canopy and are involved in pollinating certain plants. Numerous species in at least six ovoviviparous genera (Blaberidae: Epilamprinae), are amphibious or semiaquatic. They usually live on land at the edges of streams or pools, but they may spend brief periods of time in the water. About 25 genera and about 62 species of cockroaches have been found in bromeliads, where water collects in the leaf bases. Many of these species are not restricted to this habitat, but some may be truly bromeliadicolous.

In the United States, desert species of Arenivaga (Polyphagidae) migrate vertically on plants during the day and avoid the heat of spring, summer, and autumn. Between November and March nocturnal temperatures are lower, and the insects burrow into the sand among roots of shrubs. During the winter, soon after darkness, they become active during peaks of nighttime surface temperatures.

Behavior

There are three types of social behavior and communication: gregarious (aggregation), subsocial (adults care for larvae), and solitary; communication (especially during courtship behavior) is accomplished with pheromones. Vision apparently plays little or no significant role in sexual recognition, courtship, and copulation, in spite of the fact that many species have large, well-developed, pigmented eyes.

There are many records of predation on cockroaches. Among the arthropods, ants and spiders are the most important predators in the tropics. Cockroach remains have been found in the stomachs of fish, salamanders, toads, frogs, turtles, geckos, and lizards. Several species of birds eat these insects, and a Peruvian wren (“cucarachero”) apparently specializes in cockroaches. Among mammalian predators on cockroaches are opossums, porcupines, monkeys, rodents, and cats.

Cockroaches are subject to parasites, for example, viruses, bacteria, protozoa, fungi, and helminths. Among the parasite arthropods are wasps, flies, and beetles. One whole wasp family, the Evaniidae, favors only cockroach eggs. Larvae and adult cockroaches are eaten by species in three families of Hymenoptera, two of Diptera, and one of beetles. Species of Ampulex and Dolichurus (Hymenoptera: Ampulicidae) provision their nests only with cockroaches.

Many species burrow into the substrate when disturbed or during periods of inactivity. Some conceal themselves in folded dead leaves, in caves they burrow into guano, or in crevices. Some species run rapidly or fly or become immobile at the approach of an attacker. Cockroaches have mechanoreceptors, especially on their cerci, that respond to the slight acceleration of air that signals the approach of a predator. Some species that become immobile when attacked by ants cling so tightly to the substrate that their vulnerable undersurfaces cannot be harmed. Many species have defensive glands that produce a variety of irritating chemicals, the most common being trans-2-hexenal, which is sprayed forcibly on

148	Grzimek’s Animal Life Encyclopedia

Vol. 3: Insects

the attacker. Many immature cockroaches and some adults secrete a sticky proteinaceous substance on their terminal abdominal segments and cerci that gums up ant or beetle attackers.

Some tropical cockroaches have warning coloration that involves mimicry, and they resemble lampyrid beetles (fireflies), coccinellid beetles, or wasps. Virtually nothing is known about the relationships of the mimic (the cockroach) and model; in fact, in many instances the models are unknown.

Cockroaches produce sound in many ways, but two methods, namely, stridulation and expulsion of air through the second abdominal spiracles, have evolved in ovoviviparous Blaberidae: Oxyhaloinae. The stridulating structures consist of parallel striae (thickenings) on the ventral lateroposterior nargins of the pronotum and on the dorsoproximal regions of the costal veins of the tegmina. When disturbed, the insect rubs the pronotum sideways against the modified region of the costal veins.

Under normal periods of light and dark, many pest species are nocturnal and increase their activity just as it begins to get dark; activity ceases after five or six hours, and they remain quiet throughout the following day. Some feral Australian Polyzosteriinae that live exposed are diurnal and are active during the day. Domestic cockroaches may aggregate in large numbers during the day and at night move out and migrate to obtain food and water.

Feeding ecology and diet

Cockroaches seem to eat almost anything, from plants to animals. They may exhibit preferences and discriminate when given a choice. When deprived of food and water, they can live from five days (Blattella vaga) to 42 days (female Periplaneta americana). When given dry food but no water, they live for about the same period of time as insects that are starved; if they are provided with water, most live longer. Some species can live for two to three months on water alone. In bat-inhabiting caves they feed on guano, and in sewers they consume human feces. Some species live in dead trees and feed on wood.

Reproductive biology

Courtship precedes mating and is controlled by pheromones. Some females assume a calling position by raising the wings, expose intertergal membranes, expand their genital chambers, and release a pheromone to attract the male. In many species the newly emerged females, while still white and teneral, attract and mate with older males (e.g., Diploptera punctata).

Some species show little courtship behavior. The female does not mount the male, nor does she feed on or palpate his tergites; he either mounts or backs into her and makes the connection. Many cockroaches have stridulating organs, but in most species their role in courtship, if any, has not been determined. In some wingless species (e.g., Gromphadorhina and Macropanesthia) males hiss during courtship and simply

Order: Blattodea

The death’s head cockroach (Blaberus giganteus) lives in the Amazon rainforest in Peru. (Photo by George D. Dodge. Bruce Coleman, Inc. Reproduced by permission.)

back into and seize the female genitalia, and the pair remains joined, with their heads facing opposite directions. In all species, while the two are joined, the male forms and transfers a spermatophore to the female’s bursa copulatrix.

The eggs of almost all cockroaches are enclosed in a tan proteinaceous capsule called an “ootheca,” which may have as few as four or five eggs or as many as 243. When the ovaries mature, the eggs are extruded through a blob of soft, rubbery, colleterial gland secretion, and, with the help of the ovipositor valves, are lined up vertically and alternately on one side and then the other; when completed, there are two rows of eggs covered by a capsule. The eggs are extruded with the micropylar ends (the region where sperm enter the egg) and oothecal keel (the area that contains the air chambers for egg respiration) upward. The position in which the ootheca is carried at the time it is deposited (i.e., whether or not it is rotated 90°) is significant taxonomically and played an important role in the evolution of blaberid and blattellid ovoviviparity.

There are four types of reproduction: oviparity, false ovoviviparity, true ovoviviparity, and viviparity. In oviparity (all families except Blaberidae), the ootheca is dropped shortly after it is completed and while it still is in the vertical position (all Blattidae and Blattellidae: Pseudophyllodromiinae) or after it is rotated 90° to the right or left (Blattellidae, Nyctiborinae, and Ectobiinae). After the female deposits the ootheca, she leaves and has nothing more to do with the eggs. Initially, these eggs have enough yolk to complete development, but water is obtained from the substrate.

In false ovoviviparity (almost all Blaberidae and four genera of Blattellidae), the ootheca, after it is formed, is retracted into a uterus or brood sac, where it remains during gestation (e.g., Nauphoeta cinerea). The oothecal membrane is greatly reduced in the Blaberidae and less so in the Blattellidae. When first laid, the eggs have enough yolk to complete development and obtain water from the mother during gestation.

Grzimek’s Animal Life Encyclopedia

149

Order: Blattodea

An American cockroach (Periplaneta americana) female with egg case. (Photo by Kim Taylor. Bruce Coleman, Inc. Reproduced by permission.)

True ovoviviparity (only the blaberid Geoscapheinae, specifically, four Australian genera: Geoscapheus, Macropanesthia, Neogeoscapheus, and Parapanesthia) differs from false ovoviviparity in that an ootheca is not formed. The eggs pass directly from the oviduct into the uterus or atrium, where they lie in a jumbled mass until parturition. The eggs have enough yolk initially to complete development but obtain water from the mother as needed.

With viviparity (only one species, that is, Diploptera punctata, Blaberidae: Diplopterinae), the very small ootheca is rotated and retracted into the uterus. It has only about a dozen very small eggs enclosed in an incomplete membrane; the larvae are quite large when born. At first, the eggs lack sufficient yolk and water to complete development, but during gestation the embryos drink water and dissolved proteins and carbohydrates synthesized and transported by the mother’s uterus.

Many species that live underground or in dead trees burrow into soil or wood and form a chamber where the insects live and emerge to feed or carry down food (e.g., dead leaves) to the chamber. All the species of Cryptocercus (Cryptocercidae) live in and feed on decaying wood; the cockroaches have special protozoa that digest cellulose. Another group of cockroaches, the Panesthiinae, also eat wood, but their cellulose is digested by bacteria.

The panesthiine cockroaches Geoscapheus robustus and Macropanesthia rhinoceros burrow in sandy areas in Queensland, especially where the cypress pine grows. The adults make a nest of grass, roots, and dead leaves about 2 ft (0.6 m) below the surface and probably play an important role in litter turnover.

Vol. 3: Insects

In most cockroaches that carry the ootheca externally, the female deposits it soon after its formation; some females dig a hole and cover it with debris or conceal it in some other way. They then leave and have nothing more to do with the eggs. Those species that carry the ootheca externally during gestation probably provide some protection from parasites or predators. The Blaberidae protect their eggs by retracting them into a brood sac. Additional protection is afforded after the ovoviviparous species give birth and the newborn larvae aggregate, usually for relatively short times, under the female until the cuticle hardens. This is true of Byrsotria fumigata, Gromphadorhina portentosa, and Rhyparobia maderae. In Phlebonotus, Thorax, and Phoraspis, the female’s tegmina are large and arched; the wings may be reduced and the abdominal tergites depressed, forming a chamber in which the larvae hide, covered by the tegmina.

Conservation status

The greatest threat to feral cockroaches is the destruction of habitats, particularly in the tropics. Those species that are restricted to a particular niche are especially vulnerable. At least one cockroach, Ectobius duskei, the Russian steppe cockroach, has been eliminated as a result of the cultivation of wheat in virgin steppes. Other than conservationists and students of biodiversity, few people probably would object if a cockroach, especially a pest species, were eliminated. Today, support is given for the search for medically and economically important substances that are derived from animals and plants, and it is conceivable that some compounds they produce will be found to be of practical value. No species is listed by the IUCN.

Significance to humans

The biology of domesticated species that are pests of humans has been investigated thoroughly, often with the aim of controlling or eradicating them, which is virtually impossible. Some of these species are used in biology classes or in commercial or government laboratories to study physiological problems. University researchers are developing “robotic” cockroaches, using the large, wingless Gromphadorhina portentosa. Engineers and neurologists have developed a wrist- watch-sized sensory and video package to control, start, and steer the “Biobot” cockroach. One of the aims for these robots is to make possible remote measurements of environmental conditions where humans cannot easily or safely go (e.g., bombed buildings).

Cockroaches have been used as food by humans and are said to taste like shrimp. The Aborigines of Australia and the Lao Hill tribe of Thailand collect and eat raw cockroaches. The Laos in Korat eat cockroaches, and the children collect the oothecae for frying. In southern China and in Chinatown in New York City, dried specimens of Opisthoplatia orientalis are sold for medicinal purposes. Large nondomiciliary cockroaches are cultured or grown readily, and many have been maintained as pets. Probably one of the most popular is the slow-moving Madagascan hissing cockroach, Gromphadorhina portentosa.

150	Grzimek’s Animal Life Encyclopedia

Vol. 3: Insects

The fact that domesticated cockroaches live in homes, sewers, privies, and hospitals and feed on human foods and feces and cadavers makes it possible for them to be vectors of a variety of human diseases by carrying infectious organisms internally and externally. They have been known to harbor viruses, bacteria, fungi, protozoa, and helminths. At least 18 bacteria that cause human diseases have been found naturally in domesticated pest species, notably the American and German cockroaches. Blattella germanica collected from hospitals and residential areas have been found to carry various species of five genera of fungi of medical importance. The evidence for cockroaches’ transmitting human disease organisms is essentially circumstantial, but they have the potential to transmit pathogens indirectly when

Order: Blattodea

foods or utensils used to prepare foods are contaminated. Although their importance as vectors of disease is circumstantial, there is no doubt that some people are allergic to cockroaches, and hypersensitive individuals may experience asthma when they are exposed to cockroach allergens. Allergies are common among laboratory workers who study cockroaches. The culprits are commonly the German, American, and Oriental cockroaches, but other species (e.g., G. portentosa) also have been implicated. Many species of cockroaches produce defensive secretions that may cause burning sensations, vertigo, or nausea. Normal cockroach integumental secretions cause dermatitis and conjunctival edema in entomologists who frequently study or work with these insects.

Grzimek’s Animal Life Encyclopedia

151

2

1

3

5

4

6

7

8

1. Oriental cockroach (Blatta orientalis); 2. Madeira cockroach (Rhyparobia maderae); 3. Cinereous cockroach (Nauphoeta cinerea); 4. German cockroach (Blattella germanica); 5. Asian cockroach (Blattella asahinai); 6. American cockroach (Periplaneta americana); 7. Brownbanded cockroach (Supella longipalpa); 8. Suriname cockroach (Blatta surinamensis). (Illustration by Amanda Smith)

152	Grzimek’s Animal Life Encyclopedia