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

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