In the nick of time: males of the parasitoid wasp Pimpla disparis respond to semiochemicals from emerging mates.

Males of the parasitoid wasp Pimpla disparis Viereck (Hymenoptera: Ichneumonidae) aggregate on parasitized gypsy moth, Lymantria dispar, host pupae when the emergence of a prospective mate is imminent or under way. We tested the hypotheses that the developing parasitoid ("DePa") inside the host pupal case produces a pheromone that attracts and arrests mate-seeking males, and that the pheromone is most effective during the emergence of the parasitoid from the host. Results obtained in two-choice laboratory experiments, with 4-7-d-old virgin males, indicate that (1) DePa-derived semiochemicals arrest males, (2) the opening of a host pupal case strongly arrests males, and (3) the arrestment cue emanates from oral fluid secreted by both female and male parasitoids while they chew their way out of a host pupal case. This phenomenon implies that emerging females, which are haplodiploid and can reproduce without mating, do not engage in active pheromone signaling to attract males, and that mate-seeking males co-opt chemicals involved in eclosion as a mate-finding cue, taking a 50% chance that the prospective mate is a female.

Evidence for four-component close-range sex pheromone in the parasitic wasp Glyptapanteles flavicoxis.

Females of the parasitic wasp Glyptapanteles flavicoxis (Hymenoptera: Braconidae) deposit a close-range sex pheromone from their abdominal tip that attracts conspecific males and elicits wing-fanning behavior. In this study, we isolated the pheromone components and determined their role in the males' behavior. In coupled gas chromatographic-electroantennographic detection (GC-EAD) analyses of the females' body extract, four components (below GC detection) elicited strong responses from male antennae. Monitored by GC-EAD, the components were separated by flash silica gel and high-performance liquid chromatography. Y-tube olfactometer experiments with one or more components revealed that all are necessary to elicit short-range attraction and wing-fanning responses by males. These components remained below detection threshold of the mass spectrometer (approximately 10 pg) even when 4500 female equivalents were analyzed in a single injection, which attests to the potency of the pheromone and the insects' sensitivity to it.