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. fumi-gata) (Roth, 1962,1964b; Grillou, 1973). The suppression of receptivity appears to be the direct result of sensory stimulation via mechanoreceptors that are abundant within the brood sac (Brousse-Gaury, 1971a, 1971b; Roth, 1973b; Greenberg and Stay, 1974). Internal gestation of eggs, then, leads to potentially large differences between oviparous and ovoviviparous species in the sexual availability of females (Wendelken and Barth, 1987). Live-bearing females are removed from the mating pool for extended periods of time; gestation lasts 35 -50 days in N. cinerea (Roth, 1964a), 51 days in R. maderae (Roth, 1964b), and 55-65 days in Blab. craniifer (Grillou, 1973). Blattella germanica, a species that externally carries the ootheca for about 21 days before the young hatch (Roth and Stay, 1962c), is intermediate. Oviparous females that drop their oothecae shortly after their formation lack the lengthy gestation periods of ovoviviparous cockroaches (Chapter 7) and so have relatively high rates of "recidivist receptivity" (Wendelken and Barth, 1987). Potentially, then, these females mate more frequently and presumably with a greater number of males.

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