Mating strategy and chemical communication: how do females of the monogamous digger wasp Stizus continuus become unattractive to males after the copula?
Observations on the mating behaviour of the digger wasp Stizus continuus show that males are able to discriminate between emerging (virgin) and nesting (mated) females, as evidenced by the fact that they try to copulate only with the former, almost ignoring the latter. In this species, in fact, females mate only once and are receptive upon the emergence.
In insects, the most common communication channel used in the attraction and sexual recognition seems to be chemical signals, conveyed by sex-pheromones. Females of S. continuus might either actively signal their receptivity upon the emergence through attractants or use repellents after mating in order to become unattractive to males. Alternatively, males might deposit antiaphrodisiacs on their mates, making them unattractive to further mating attempts by rivals, assuring their own paternity.
Since there is increasing evidence that sexual pheromones in Hymenoptera are present on the surface of the cuticle, I focused on the characterization of males’ and females’ cuticular hydrocarbons (CHC) to demonstrate the presence of chemical communication between the sexes and to elucidate the possible roles of such substances in determining attraction and other interactions between sexes.
For this purpose, I combined chemical analysis and field tests: I first extracted and analyzed through GC-MS the chemical profiles of males, virgin and mated females, comparing the obtained chromatograms through multivariate statistical analysis; then I experimentally removed or altered the CHC blend, testing its effect in behavioural assays.
|
