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 Pan-chlora 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 bigut-tata 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. Platyzoste-ria 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 Muellerian 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." Vrsansky (2003) described beautifully preserved fossils of small, beetle-like cockroaches that were day active in Mesozoic forests (140 mya). Extant species of Prosoplecta (Pseudo-phyllodromiinae) (Fig. 1.3) have markedly convex oval or

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).

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 Ana-plextinae 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 Blat-taria.

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, Sal-ganea, 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 desert-burrowing Arenivaga, as well as the soil- and wood-burrowing 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 Mega-loblatta 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.

Fig. 1.5 One of the largest and one of the smallest known cockroaches. Left, adult female of Mega-loblatta 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 stern-ites 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).

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