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

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