TEMPORAL MANIPULATION OF EJACULATE COMPONENTS BY NEWLY FERTILIZED DROSOPHILA-MELANOGASTER FEMALES

Observations of newly mated Drosophila melanogaster females suggest th at females control the times at which components of the ejaculate caus e behavioural and physiological changes characteristic of fertilized f emales. Females that were assayed immediately after they mated elicite d as much courtship as they did when they were virgins, but were unrec eptive to copulation. Within a few minutes of when they disengaged fro m copulation, most females performed ovipositor extrusion, which has b een classified as a rejection behaviour, in response to courting males or males that had previously performed courtship. Most females that w ere assayed immediately after mating had already ovulated. The females , however, do not begin to lay eggs until 4-6 h after mating,at which time they elicit very little courtship (Scott & Richmond 1985, Anim. B ehav., 33, 817-824). Our observations suggest that neither ovipositor extrusion nor male-synthesized pheromones that are transferred to fema les' cuticles during copulation inhibit males' courtship of newly fert ilized females. Thus, males cannot determine that newly fertilized fem ales are unreceptive to copulation. These observations a.lso indicate that the failure of newly fertilized females to mate with males is not a consequence of the females' inability to elicit vigorous courtship. (C) 1998 The Association for the Study of Animal Behaviour.