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

Fig. 8.7 Nymphs of Cryptocercus punctulatus cooperatively feeding on a sliver of wood. Photo by
C.A. Nalepa.
wagging, or to scrape it off by dragging it along the side
of the gallery (CAN, unpubl. obs.).
It should be noted that in Cryptocercus there are cooperative
as well as competitive behaviors among nymphs
when procuring food. Wood is not only nutritionally
poor and difficult to digest, but physically unyielding.
Like young nymphs in aggregations, early developmental
stages of Cryptocercus may need the presence of conspecifics
to help acquire meals when they begin including
wood in their diet. Nymphs have been observed feeding
cooperatively on wood slivers pulled free by both siblings
(Fig. 8.7) and adults (Nalepa, 1994; Park and Choe,
2003a).
Cost of Parental Care
Most cockroaches that exhibit parental care are subject to
risks associated with brood defense and invest time in
taking care of offspring. Other costs vary with the form
and intensity of parental care. Brooding, for example, is a
small investment on the part of the female in relation to
potential returns (Eickwort, 1981). In females that carry
offspring on their bodies, the burden may hinder locomotion
and thus the ability to escape from predators. Energy
expended on nest construction can detract from a
parent’s capacity for subsequent reproduction in those
species where parental care occurs in excavated burrows.
Insects that utilize nests may also invest time and energy
in provisioning and hygienic activities (Tallamy and
Wood, 1986). Feeding offspring on bodily secretions may
drain stored reserves otherwise devoted to subsequent
bouts of oogenesis. The metabolic expenditure may be
particularly high in wood-feeding species, whose diet is
typically low in nitrogenous materials. The high cost of
parental care in Cryptocercus may account for their functional
semelparity (Nalepa, 1988b), and has been proposed
as a key precondition allowing for the evolution of
eusociality in an ancestor they share with termites (Chapter
9). It is of interest then, that, another wood-feeding
cockroach (Salganea matsumotoi) that lives in biparental
groups and is thought to exhibit extensive parental care
appears to have more than one reproductive episode
(field data) (Maekawa et al., 2005).
In insects that do not nest in their food source, providing
care to young may conflict with feeding opportunities,
particularly in species whose diet consists of dispersed
or ephemeral items that require foraging over
substantial distances. One solution to is to carry one
brood while gathering nutrients for subsequent brood
development (Tallamy, 1994). To test this hypothesis, it is
necessary to determine (1) if females feed while externally
carrying nymphs, and (2) if females carrying nymphs are
concurrently developing their next set of eggs, incubating
eggs in the brood sac, or building reserves for the next
brood. We found relevant information on two species. A
Pseudophoraspis nebulosa female caught in the field with
numerous neonates clinging to the undersurface of her
abdomen was dissected, and her brood sac was empty
(Shelford, 1906a). In Tho. porcellana, newly hatched
nymphs remain in association with their mother for 45
days. After partition another ootheca is formed in 15 to
20 days, and gestation takes 45–52 days. There is therefore
a period of time when the female is both internally
incubating an ootheca in her brood sac and externally
carrying nymphs on her back. However, these are sluggish
insects that remain stationary in the leaves on which they
148 COCKROACHES