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

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
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