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 monan-drous 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 Eu-blaberus posticus are fertile for life, and remating does not improve reproductive performance (Roth, 1968c); nonetheless, remating has been observed (Darlington, 1970).

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