Multiple mating and its effects in the lightbrown apple moth, Epiphyas postvittana (Walker)

Abstract

Multiple mating and some of its effects were investigated in the tortricid moth, Epiphyas postvittana, a species in which females are generally monandrous. Males were capable of mating a relatively large number of times (mean of 6.6 matings throughout their lifetime). Although less common, multiple mating of females occurred and was related to the male that the female mated with initially. A small proportion (approximately one fifth) of females that mated with a virgin male, remated; this was not related to the size of the spermatophore from the first mating. Females that mated with a previously mated male were more likely to remate with an increase in the number of previous matings of the male. These data suggest that remating of a female occurs as a result of a deficiency of a substance in the male, either naturally, in the case of some virgin males, or through serial depletion in multiply mated males, that triggers a refractory behaviour in females. The mating status of males affected both pheromone titre of, and number of fertile eggs laid by females they mated with; copulation with a multiply mated male generally resulted in a lesser pheromonostatic effect and fewer fertile eggs laid by a female, compared to when a female mated with a virgin male. Moreover, with an increase in number of previous matings of the male, there was an increase in the proportion of infertile matings (i.e. matings after which the female did not lay any fertile eggs). Age of the male at first mating did not affect pheromone production, proportion of rematings, or number of eggs laid by females that the males mated with. Age of the female at mating also did not affect the proportion of females that remated, but it did affect the number of eggs laid after mating, with females laying fewer fertile eggs and having a higher incidence of infertility when mated at an older age. The three behavioural/physiological changes, laying of fertile eggs, pheromonostasis, induction of refractory behaviour, in mated females (relative to virgin females) appear to be elicited by three different substances transferred from the male during copulation.