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

clinging nymphs inside, rendering both the female and
the nymphs she surrounds relatively impervious to attacks
by ants (Fig. 1.11B). At least nine nymphs may be
enclosed when the female assumes the defensive position.
Other genera with the ability to conglobulate (e.g.,
Pseudoglomeris) may also exhibit this type of parental
care. A similar defensive behavior occurs in species where
the female “cups” her underside against a hard substrate
(Fig. 8.6). In Trichoblatta sericea, well-developed pulvilli
and claws of first-instar nymphs allow them to cling to the
underside of the female for the first 2 to 3 days after hatching.
The female secretes a milky fluid from her ventral
side, which probably serves as food for the nymphs.
Neonates isolated from their mother did not survive past
the second instar (Reuben, 1988).
Parental Care in a Nest or Burrow
Nests and burrows typically reduce the biological hazards
of the external environment and reinforce social behavior
(Hansell, 1993). The structures offer protection from
natural enemies and act as a buffer against temperature
and moisture fluctuations. In subsocial cockroaches
found in nests, one or both parents also actively defend
the galleries against predators and conspecific intruders.
Because these cockroaches nest in or near their food
source (wood, leaf litter), parents can forage without leaving
or carrying their offspring. Australian soil-burrowing
cockroaches nest only where their food source is ample
and forage close to the entrance (Macropanesthia), and
so are absent from their family for only brief periods of
time (Rugg and Rose, 1991; Matsumoto, 1992). Females
Fig. 8.6 Maternal care in an unidentified apterous cockroach
collected in Namibia, ventral view. The female was clinging to
a rock, with the elongated edges of the tergites serving to raise
her venter above the substrate and form a brood covering
“cup.” The presence of ants (upper-right quadrant) in this field
photo suggests that the behavior functions to defend young
nymphs, although it is possible the female also supplies them
with nutriment. Photo and information courtesy of Edward S.
Ross.
with young are quite aggressive (D. Rugg, pers. comm. to
CAN).
Biparental care in a nest arose at least twice among
wood-feeding cockroaches: in the ovoviviparous Panesthiinae
and in the oviparous Cryptocercidae. These insects
typically nest in damp, rotted logs, utilizing the
wood itself as a food source; consequently, the young are
never left untended. A wood-based diet may warrant the
cooperation of both parents; wood-feeding has favored
paternal investment not only in cryptocercids and some
panesthiines, but also in passalid and scolytid beetles
(Tallamy and Wood, 1986; Tallamy, 1994).
Cryptocercus is the only known oviparous cockroach
with well-developed parental care, and is discussed in
Chapter 9 in the context of its sister group relationship to
termites. A recent study found that adult presence has a
significant effect on offspring growth in families of C.
kyebangensis (Park and Choe, 2003a), but the relative influence
of parental care and group effects are yet to be determined.
In gregarious Periplaneta, for example, single
nymphs raised with adults grow and develop as rapidly as
grouped nymphs (Wharton et al., 1968). All studied
species in the wood-feeding blaberid genus Salganea live
in biparental families (Matsumoto, 1987; Maekawa et al.,
1999b, 2005). In Sal. taiwanensis, nymphs cling to the
mouthparts of their parents and take liquids via stomodeal
feeding (Fig. 8.3B). Removal of neonates from
parental care results in high mortality; removed nymphs
that live have a significantly longer duration of the first
instar (T. Matsumoto and Y. Obata, pers. comm. to CAN).
Two different social structures have been reported
for Australian wood-feeding panesthiines: both family
groups and aggregations. Shaw (1925) reported that both
Panesthia australis and Pane. cribrata ( laevicollis) live in
family groups consisting of a pair of adults and nymphs
in various stages of development. Matsumoto (1988)
more recently studied Pane. australis, and found that of
29 social groups collected, the majority were families: 14
consisted of a female with nymphs, two were a male with
nymphs, and two were an adult pair with nymphs.
Groups never contained more than a single adult of either
sex or an adult pair together with nymphs. The age of
nymphs in the group ranged widely, however, so it is possible
that the nymphs in these groups were aggregated individuals
rather than a sibling group (T. Matsumoto, pers.
comm. to CAN). The field studies of H. A. Rose (pers.
comm. to CAN) indicate that neither Pane. australis nor
any of the other wood-feeding Australian panesthiines
are subsocial. Rugg and Rose (1984b) and O’Neill et al.
(1987) found that while adult pairs with nymphs could be
found in Pane. cribrata (12% of groups), the most commonly
encountered groups (29%) were harems, consisting
of a number of adult females, together with a single
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