POSTCOPULATORY MALE-BEHAVIOR, SPERM PRECEDENCE AND MULTIPLE MATING INA SOLITARY PARASITOID WASP

Female Aphytis melinus (Hymenoptera: Aphelinidae), previously thought to be unreceptive after their first mating, mated multiply in the held at an incidence of at least 3.2-6.7%. In spring the adult sex ratio w as female biased while in autumn it was male biased. Following copulat ion, male A. melinus guard females for an average of 149 s during whic h they display behaviour identical to that seen prior to copulation. B ehavioural experiments using genetically marked pairs of males were se t up to test several hypotheses concerning the adaptive significance o f guarding and postinsemination displays. The behaviour seen during gu arding probably keeps the female quiescent but does not influence the fate of second-male sperm. Second males that did not guard achieved eq ual paternity to those that did. Guarding and its associated post-copu latory behaviour helped 'switch off' female receptivity. The percentag e of second males that managed to achieve intromission, if attempting to mate with a previously guarded female, dropped from 97 to 70%. Furt hermore, males courting a previously guarded female scored significant ly more contacts, unsuccessful mounts, time to achieve the successful mount, wingbeats, and time in the successful pre-coital mount. Last-ma le sperm precedence did not occur. Second males shed 30.5% of the prog eny if the guarding male was immediately dislodged and 14.2% of the pr ogeny if the first male was allowed to complete guarding. Thus by dela ying rival male courtship through guarding, first male A, melinus decr eased the chance that the female would mate again. Guarding also reduc ed the proportion of progeny sired by a second mating male.