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

1987). In 12% of copulations of D. punctata observed by
Wyttenbach and Eisner (2001), the teneral female pushed
at the male with her hind legs until he disengaged; in each
case the female subsequently accepted a second male. Females
of N. cinerea require a longer period of courtship
prior to copulation if they can detect the chemical traces
of former female consorts on a male (Harris and Moore,
2005)—the cockroach equivalent of lipstick on his collar.
After genitalic engagement, they can apparently determine
if a male is depleted of sperm or seminal products
because of those recent matings. After the first copulation
“males are less adept at grasping the female,” and pairs often
remained joined for only a few seconds or minutes;
no spermatophore is transferred. The female pushes the
male with her hind legs, forcing him to release her (Roth,
1964b). Further evidence of female control of copulation
in N. cinerea comes from transection experiments. When
female genitalia were denervated males could not grasp
the female properly and they stayed connected for only a
few seconds (Roth, 1962).
Copulatory Success
Several studies report that male B. germanica have an
abysmal record of successfully courting and copulating
with females provided to them. Curtis et al. (2000) exposed
each of 9 virgin males to serial batches of 2–10 virgin
females throughout their lifetime (total of 341 females).
Only 27 females were successfully inseminated.
One-third of the males sired no offspring, and a further
third inseminated just a single female. In a study of 55 virgin
pairs by Nojima et al. (1999b), 84% of males courted
females, 65% of the females responded by tergal feeding,
but only 37% made the transition to copulation. Roth
and Willis (1952a) did a detailed analysis of courtship and
copulation in 10 pairs of German cockroaches (Table
6.2). Males courted rather vigorously in most cases; male
8, for example, courted the female 48 times in 30 min.
Four females (pairs 3, 4, 5, 10) were nearly or completely
unresponsive to male courtship, and 5 females responded
by tergal feeding but refused to mate (pairs 2, 6–9). Just
one of the 10 observed pairs successfully copulated. This
puzzling lack of copulatory success has been noted in at
least 2 other cockroach species. O’Neill et al. (1987) reported
that in the majority of observed courtships, females
of Pane. cribrata (Blaberidae) were not receptive.
Males of P. americana (Blattidae) are rarely readily acceptable
to the female (Gupta, 1947); only one in 20 attempted
matings appeared successful in Rau’s (1940)
study of the species.
Female Loss of Receptivity
Although female sexual receptivity is inhibited as a result
of mating in all cockroach species studied (Barth, 1968a),
the fine points of its physiological control are far from
straightforward. Not only do details of regulation differ
among species, but the various components of mating behavior
are controlled in distinct ways within a species
(Roth and Barth, 1964). “It is essential to be wary of generalization”
(Grillou, 1973). Mechanical cues are of primary
importance in examined cockroaches, but chemical
influences cannot always be ruled out (Engelmann,
1970). Interaction with male genitalia, the presence of the
spermatophore in the female genital tract, and sperm or
seminal fluid in the spermathecae have all been reported
as mechanical cues influential in the initial or sustained
loss of receptivity in cockroaches following mating (Roth
and Stay, 1961; Roth, 1964b; Stay and Gelperin, 1966;
Smith and Schal, 1990; Liang and Schal, 1994). The phenomenon
is best studied in three cockroach species, the
blattellids B. germanica and Su. longipalpa, and the blaberid
N. cinerea. In the blattellids, one aspect of female receptivity,
calling, is turned off by two successive mechanical
cues provided by males during copulation. First, the
insertion of a spermatophore results in the immediate
cessation of calling. The behavior can be suppressed in
experimental females by a spermatophore in the genital
tract, by the insertion of a fake spermatophore, and by
copulation with vasectomized males. The spermatophore
effect, however, is transient. The presence of sperm or
seminal fluids in the spermathecae is the stimulus that
maintains the suppression of calling behavior in the first
as well as the second ovarian cycles. The ventral nerve
cord plays a crucial role in the transmission of the inhibitory
signals (Smith and Schal, 1990; Liang and Schal,
1994). Signals transferred via the nerve cord also decrease
locomotor activity in females (Lin and Lee, 1998).
The suppression of receptivity in N. cinerea following
mating requires a single cue: mechanical stimulation
caused by the insertion of the spermatophore into the
bursa copulatrix (Roth, 1962, 1964b). The insertion of
glass beads into the bursa results in the same loss of receptivity,
manifested as a lack of a feeding response to
male tergal displays. Spermatophore removal experiments
indicate that female receptivity is lost immediately after
the male reproductive product is firmly inserted into the
bursa but prior to the migration of sperm into the spermatheca.
Cutting the nerve cord above the last abdominal
ganglion in N. cinerea renders the female “permanently”
receptive. However, it is curious that the ventral
nerve cord in most females must remain intact for two
days for female receptivity to be inhibited. Vidlička and
Huckova’s (1993) finding that female N. cinerea become
unresponsive to male sex pheromone about 2 days after
mating is consistent with the results of these transection
studies. Roth (1970b) suggests the possibility that mating
stimuli are transmitted rapidly to the last abdominal gan-
MATING STRATEGIES 107