Institut für Biologie I (Zoologie), Universität Freiburg, Hauptstr. 1, 79104 Freiburg, Germany.
The male sexual response of A. curtula, i.e. the grasping with the tongs-like parameres of the genitalia towards the female's body, is released by a female sex pheromone, alkenes from the cuticle (e.g. (Z7)-tricosene). After establishing contact with these sensilla-rich claspers, the coupling of genitalia is accomplished. The grasping response rate is only slightly reduced in first encounters with recently copulated females. However, after touching the abdominal tip of such a female, males break off further contact and they do not respond to her in subsequent encounters. These effects are also observed with females which have been freshly killed by freezing, but elicit identical behavioral responses, including copulation. Thus, alteration of the chemical information by the female is unlikely; anti-aphrodisiacs are apparently transferred by the male. The cuticular hydrocarbons of A. curtula males comprise significantly larger amounts of 5-methylheneicosane and 5-methyltricosane than virgin females. Hydrocarbons were locally adsorbed from the female's abdominal tip before and after copulation by contact with a 100 µ PMDS coated needle of a solid phase microextration syringe and subsequently analysed by GC/MS. A significant increase of 5-methylalkanes was observed during copulation. Their source may be the male's cuticle during coupling, the spermatophore or the aedeagal gland.