Female-derived sex pheromone mediates courtship behaviour in the parasitoid Lariophagus distinguendus

Courtship behaviour of the polyphagous ectoparasitoid Lariophagus distingue ndus Forst. (Hymenoptera, Pteromalidae) was studied. The initial behavioura l element of the courtship sequence is a characteristic wing fanning shown by the males at encounters with females. Wing fanning and arrestment of the males was elicited by paper discs treated with dichloromethane extracts fr om virgin females showing the existence of a female-derived sex pheromone. The pheromone is only active at a distance between 0-5 mm suggesting low vo latility of the active compound(s). Females mate only once, and the pheromo ne is still perceived by males at least 5 days after female mating. Males e xposed to dissected female heads, thoraces and abdomens, showed wing fannin g towards all segments. However, extracts from female abdomens were signifi cantly more active than those from heads or thoraces suggesting the pheromo ne source to be located in the abdomen.