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

are therefore best classified on the basis of female behavior.
However, it is difficult to determine how many mating
partners a female has in the wild, and, as might be expected
for insects that are mostly cryptic and nocturnal,
field studies of mating behavior are rare.
One Male, One Copulation
Females of at least two cockroach species are reported to
be monandrous in the strictest sense of the word. Once
mated, Neopolyphaga miniscula (Jayakumar et al., 2002)
and Therea petiveriana (Livingstone and Ramani, 1978)
females remain refractory to subsequent insemination
for the rest of their lives; the latter repel suitors by kicking
with their hind legs.
One Male, Multiple Copulations
Wood-feeding cockroaches in the genus Cryptocercus
may be described as socially monogamous; males and females
establish long-term pair bonds and live in family
groups. Genetic monogamy is yet to be determined, but
opportunities for extra-pair copulations are probably
few. When paired with a female, males fight to exclude
other males from tunnels (Ritter, 1964), and adults of
both sexes in families defend against intruders (Seelinger
and Seelinger, 1983). In the two copulations observed in
C. punctulatus, one lasted for 34 min and the other for
42 min (Nalepa, 1988a); sneaky extra-pair copulations
therefore seem unlikely. The best opportunity for cheating,
if it occurs, would be after adult emergence but prior
to establishment of a pair bond. Adult males and adult females
each can be found alone in galleries, particularly
during spring and early summer field collections (Nalepa,
1984).
Typically, males and females pair up during summer,
overwinter together, and produce their sole set of offspring
the following summer. Although sperm from a
single copulation are presumably sufficient to fertilize
these eggs (average of 73), pairs mate repeatedly over the
course of their association. There is evidence of sexual activity
the year before reproduction, immediately prior to
oviposition, during the oviposition period, after the hatch
of their oothecae, and 1 yr after the hatch of their single
brood (Nalepa, 1988a). Prior to oviposition, repeated
copulation may function as paternity assurance or perhaps
nutrient transfer, but mating after the eggs are laid
is more difficult to explain. Rodríguez-Gironés and Enquist
(2001) note that mating frequency is particularly
high in species where males associate with females and
assist them in parental duties. Superfluous copulations
evolve in these pairs because females attempt to sequester
male assistance and males are deprived of cues about female
fertility. It would be of interest to determine if this
pattern of repeated mating behavior occurs in other socially
monogamous, wood-feeding cockroaches like Salganea;
these also live in family groups with long-term
parental care (Matsumoto, 1987; Maekawa et al., 2005).
Multiple Males, One Copulation
per Reproductive Cycle
In most studied cockroaches female receptivity is cyclic.
It declines sharply after copulation and is not restored until
after partition. In some species it takes several reproductive
cycles before another mating partner is accepted,
in others receptivity is restored following each reproductive
event. Females, then, may be described as monandrous
within each period that they are accepting mates,
but polyandrous over the course of their reproductive life.
Because they store sperm, it is only during the formation
of the first clutch of eggs that their partners are under little
threat from sperm competition. The pattern of cyclic
receptivity occurs in both oviparous and live-bearing
cockroaches. Both Blattella germanica (Cochran, 1979b)
and B. asahinai (Koehler and Patternson, 1987) may copulate
repeatedly, although a single mating usually provides
sufficient sperm to last for the reproductive life of
the female. Periplaneta americana females alternate copulation
with oothecal production, and may mate as soon
as 3–4 hr after depositing an egg case (Gupta, 1947). A
pair of Ellipsidion humerale ( affine) were observed
copulating four times within a month, alternating with
oothecal production (Pope, 1953). Similarly, blaberid females
ordinarily mate just once prior to their first oviposition.
After eclosion of the nymphs, they may then enter
another cycle of receptivity, mating, oviposition, and egg
incubation (Engelmann, 1960; Roth, 1962; Roth and
Barth, 1967; Grillou, 1973). Once mated, female Eublaberus
posticus are fertile for life, and remating does
not improve reproductive performance (Roth, 1968c);
nonetheless, remating has been observed (Darlington,
1970).
Multiple Males, Multiple Copulations
per Reproductive Cycle
Reports of multiple mating by a female within a single reproductive
cycle exist, but they are the exception rather
than the rule among examined species. In his study of
more than 200 female B. germanica, Cochran (1979b)
recorded just a single instance of a female mating twice
prior to her first egg case. In their extensive studies of the
same species, Roth and Willis (1952a) noted one pair that
copulated twice within a 24-hr period. Hafez and Afifi
(1956) report that in Supella longipalpa “copulation may
90 COCKROACHES