Kairomonal response of the parasitoid, Bracon hebetor Say, to the male-produced sex pheromone of its host, the greater Waxmoth, Galleria mellonella (L.).

Bracon hebetor is a larval ectoparasitoid that utilizes several pests belonging to the family Pyralidae (Lepidoptera) as hosts. In the present study, we analyzed the kairomonal response of this wasp to the male-produced sex pheromone of a host, the greater wax moth Galleria mellonella, an economically important pest of honeybees, Apis mellifera. Coupled gas chromatography-electroantennographic detection (GC-EAD) revealed three compounds in headspace collections from male G. mellonella that elicited responses from B. hebetor antennae: decanal and the previously identified sex pheromone components, nonanal and undecanal. Y-tube olfactometer tests that used naïve, mated wasps showed that females, but not males, were highly attracted to (a) male G. mellonella headspace samples, (b) two synthetic blends of nonanal and undecanal (in ratios matching that found in male moth samples), and (c) the two aldehydes tested individually. Further, female wasps did not discriminate between a blend of aldehydes and male G. mellonella headspace. In dose-response trials that used octanal, nonanal, decanal, and undecanal, no difference in EAG responses of the two sexes was observed, except for undecanal at the second highest dose, for which female antennae showed significantly larger responses than did male antennae. When the two binary blends were tested at different doses, female wasps were significantly attracted to the two highest doses (1 microg and 10 microg), but not to the lowest dose (100 ng). Our results show that females of this economically important parasitoid utilize the male-produced sex pheromone of a host as an indirect cue to guide them to potential oviposition sites.