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

include Blaberus spp., which readily bury themselves
in dirt or loose guano (Blatchley, 1920; Crawford and
Cloudsley-Thompson, 1971), and Pycnoscelus spp., found
in a wide variety of habitats as long as they can locate appropriate
substrate for burrowing (Roth, 1998b; Boyer
and Rivault, 2003). All stages of Pyc. surinamensis tunnel
in loose soil, and are also reported from rodent burrows
(Atkinson et al., 1991). The sand-swimming desert cockroaches
fall into this category, as well as species such as Ergaula
capensis, where females and nymphs burrow into
well-rotted coconut stumps (Princis and Kevan, 1955), as
well as the dry dust at the bottom of tree cavities (Grandcolas,
1997b). Blattella asahinai is known to burrow into
leaf litter and loose soil; they are sometimes pulled up
along with turnips in home gardens (Koehler and Patterson,
1987). Individuals of Heterogamodes sp. are known
to bury themselves in sand or earth (Kevan, 1962). Several
Australian species (Calolampra spp., Molytria vegranda)
seem to spend the daylight hours underground,
emerging to feed after dark (Rentz, 1996; D. Rentz, in
Roth, 1999b). When collected during their active period
or in light traps they usually sport sand grains on their
bodies. In caves, Eu. posticus nymphs burrow in the surface
of loose guano. They may be completely concealed,
or may rest with their heads on the surface with their antennae
extended up into the air. If the guano is compacted,
the cockroaches remain on its surface and are attracted
to irregularities such as the edge of a wall, a rock,
or a footprint (Darlington, 1970). The recently described
species Simandoa conserfariam congregates in groups of
20 to 50 individuals of all ages deep within the guano of
fruit bats; none have been observed on the surface (Roth
and Naskrecki, 2003).
Crevice Fauna
The cockroaches considered crevice fauna are those that
insert themselves into preexisting small voids in generally
unyielding substrates. These include species found under
bark, in bark fissures, in the bases of palm fronds and
grass tussocks, in hanging dead leaves, empty cocoons,
and hollow twigs, under logs and rocks, in piles of stones,
rock crevices, and the excavated galleries of other insects.
An example of the latter is the Malaysian cockroach Margattea
kovaci, which lives in bamboo internodes accessed
via holes excavated by boring Coleoptera and Lepidoptera
(D. Kovach, pers. comm. to LMR). Burrowing
and crevice-dwelling cockroaches can be categorically
difficult to separate, particularly species that shelter under
rotting logs, in rolled leaves, or in the litter wedged
into the base of bunch grasses, spinifex, or the leaf axils of
many plants. The spaces under rocks and stones are a particularly
important microhabitat for cockroaches in unforested
areas. Species of the genera Deropeltis and Pseudoderopeltis,
for example, are abundant under the boulders
“bestrewing the Masai steppe country” (Shelford,
1910b). Rock-soil interfaces may also act as corridors between
habitats, serving as oases for cockroaches moving
between caves, or between patches of forest (Lawrence,
1953). Some cockroach species are morphologically specialized
to inhabit the wafer-thin crevices under bark or
rocks (Fig. 1.10). The incredibly flattened bodies of tropical
Australian Mediastinia spp. allow them to slip into the
unfolding leaves of gingers, lilies, and similar plants during
the day. At night they move to new quarters as the
leaves of their previous shelters unfold (D. Rentz, pers.
comm. to CAN).
In Solid Substrate
Cockroaches that excavate permanent burrows in solid
materials such as wood or compacted soil are more specialized
than those that use loose substrate or crevices.
They typically exhibit a suite of ecological and behavioral
features associated with their fossorial existence, and external
morphology tends to converge. There are two major
groups that fall into this category, the Cryptocercidae
and the Panesthiinae, the latter of which includes the soilburrowing
cockroaches. There are other species whose
morphology suggests they are strong burrowers, but little
has been published on their field biology. The hissing
cockroaches, including Gromphadorhina portentosa, have
the general demeanor of burrowers. In a recently published
book on the natural history of Madagascar, however,
the only mention of these cockroaches is as prey for
some vertebrates and as hosts for mites (Goodman and
Benstead, 2003).
Burrows in solid substrates offer mechanical protection,
as well as shelter from some classes of parasites and
predators. The fact that dispersal in both the Cryptocercidae
and Geoscapheini occurs following rainfall when
excavation is likely to be more efficient (Rugg and Rose,
1991; Nalepa, 2005) suggests that burrow creation is energetically
costly. Pathogens may accumulate in tunnels,
and occupants may not be able to escape if a predator enters
the excavated space. It is unknown if burrowing cockroaches
have strategies for dealing with flooded burrows,
or with the often peculiar O 2
to CO 2
ratios that may occur.
In Wood
Dead wood is a tremendously diverse resource that varies
with plant taxon, size (branch to bole), location (forest
floor to suspended in canopy), degree and type of rot, orientation
(standing versus prone), presence of other invertebrates,
and other factors. Cockroach species from
46 COCKROACHES