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

posited in or near the hole, and adjusted into position
with the mouthparts. A mixture of saliva and finely masticated
substrate is applied to the surface of the egg case,
and the remaining gaps are filled with dry material. The
whole operation can last more than an hour (McKittrick
et al. 1961; McKittrick, 1964). Females can be quite selective
in their choice of building material. Rau (1943) noted
that Blatta orientalis chooses large grains of sand and discards
the small ones. In P. americana the egg case may be
plastered with cockroach excrement dissolved in saliva
(Rau, 1943). It should be noted in this regard that, like
termites, cockroaches produce a heterogeneous mix of
excretory products (Nalepa et al., 2001a). These may be
distinguished in some species by the behavior of the
excretor, the reaction of conspecifics in the vicinity, and
the nature of the fecal material. Cockroaches that are domestic
pests are well known for producing both solid fecal
pellets and smears attached to the substrate. Both
Lawson (1965) and Deleporte (1988) describe distinct
and systematic defecation behaviors in P. americana that
are reminiscent of termites during nest building. These
include backing up prior to defecation, then dragging the
tip of the abdomen on the substrate while depositing a fecal
droplet.
Some cockroach species actively modify their living environment.
Arenivaga apacha dwell in the burrows of
kangaroo rats, within which they construct small living
spaces lined with the nest material of their host (Chapter
3). The soil associated with these spaces is of unusually
fine texture because the cockroaches work the soil with
their mouthparts, reducing gravel-sized lumps to fine
sand and silt-textured soil (Cohen and Cohen, 1976). Eublaberus
posticus shapes the soft mass of malleable bat
guano along the base of cave walls into irregular horizontal
galleries (Fig. 9.3). These are subsequently consolidated
by calcium carbonate from seepage water (Darlington,
1970). It is unclear whether the cockroaches
actively build these structures or whether the hollows are
epiphenomena, by-products of the insects’ tendency to
push themselves under edges and into small irregularities
(Darlington, pers. comm. to CAN). The observation by
Deleporte (1985) that various developmental stages of P.
americana dig resting sites in clay walls suggests the former.
Cockroaches in the Cryptocercidae in many ways exhibit
nest construction and maintenance behavior comparable
to that of dampwood termites (Termopsidae).
When initiating a nest, adult Cryptocercus actively excavate
galleries; their tunnels are not merely the side effects
of feeding activities. They eject frass from the nest, plug
holes and gaps (Fig 9.4A), build pillars and walls to partition
galleries, and erect barriers when their galleries approach
those of families adjacent in the log (Nalepa, 1984,
Fig. 9.3 Shelters fashioned from wet guano along the base of
cave walls by Eublaberus posticus, Tamana main cave, Trinidad;
note cockroaches in crevices. The insects may actively construct
these structures, or they may result from the cockroach
tendency to wedge into crevices. From Darlington (1970);
photo and information courtesy of J.P.E.C. Darlington.
Fig. 9.4 Constructions of Cryptocercus punctulatus. (A) Detail
of material used to plug holes and seal gaps; here it was sealing
the interface between a gallery opening and the loose bark that
covered it. Both fecal pellets (arrow) and small slivers of wood
are present. (B) Sanitary behavior: fecal paste walling off the
body of a dead adult (arrow) in a side chamber. An adult male
was the only live insect present in the gallery system. Photos by
C. A. Nalepa.
154 COCKROACHES