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

Fig. 6.14 (A) Sagittal section of the female genitalia of Gromphadorhina portentosa (Blaberidae).
(B) Diagrammatic sagittal section of blaberid female genitalia with ootheca in brood sac. From
McKittrick (1964).
2003). If multiple matings do increase female fitness, it
follows that the control of female sexual receptivity is a
source of conflict between the sexes, and females are expected
to evolve resistance to the stimuli males use to induce
receptivity loss (Arnqvist and Nilsson, 2000). That
does not appear to be the case in N. cinerea. Copulation
is known to confer numerous fitness benefits on female
cockroaches (discussed below), but within the framework
of cyclic receptivity typical of N. cinerea there is currently
no evidence that more than one mate within the first
reproductive cycle is advantageous. Moreover, morphological
and experimental evidence suggests that spermatophore
placement and therefore loss of receptivity in
N. cinerea is likely under female control, suggesting that
there is no conflict of reproductive interest between the
sexes on this issue. Not only do females have morphological
features specialized for proper spermatophore placement
and retention, these features are regulated by her
nervous system. Receptivity in N. cinerea is suppressed
only if the spermatophore is firmly placed and properly
positioned (Roth, 1964b). While in some blaberids a large
amount of glue-like secretion cements the spermatophore
into place, in Nauphoeta and several related genera
the bursa is largely responsible for spermatophore retention
(Graves, 1969). The bursa is deep, is extensively
membranous, and almost completely wraps around the
correspondingly elongated spermatophore. If the nerve
cords are severed prior to mating in female R. maderae,
another species with a deep, membranous bursa, 70% of
males were not able to insert the spermatophore properly.
They were placed elsewhere in the genital atrium or
dropped by the male without being transferred. In many
cases the male had pierced the wall of the brood sac and
the spermatophore was in the female’s body cavity. “It
seems the female takes an active role in the proper positioning
of the spermatophore in the bursa copulatrix, and
an intact nerve cord is needed for proper muscular movements
of the female genitalia” (Roth and Stay, 1962a).
Loss of Receptivity during Gestation
Pregnant blaberid females typically do not respond to
courting males. The physical presence of an ootheca in
the brood sac inhibits mating behavior, and its removal
leads to the return of receptivity (N. cinerea, Byr. fumigata)
(Roth, 1962, 1964b; Grillou, 1973). The suppression
of receptivity appears to be the direct result of sensory
MATING STRATEGIES 109