Males of the parasitic wasp Nasonia vitripennis (Hymenoptera: Pteromalidae) attract virgin females by releasing a sex pheromone composed of (4R,5R)- and (4R,5S)-5-hydroxy-4-decanolide (HDL). The pheromone is biosynthesized in the rectal vesicle of males. In the present study, we investigated the mechanism and behavioral context of pheromone release, and determined the range of activity and the longevity of the chemical signal. Our data show that the sex pheromone of N. vitripennis is substrate-borne and is deposited on surfaces by dabbing movements of the abdominal tip, a behavior previously described in N. vitripennis males as 'abdomen dipping'. Chemical markings deposited by a single male were highly attractive to virgin females. Chemical analyses revealed the presence of HDL in surface washings of marked areas, and HDL amounts correlated with male marking activity. Pheromone deposition occurred spontaneously without any additional cues being present, but marking intensity increased greatly after copulation or after a single contact with a virgin female. In contrast, marking intensity was not influenced by the presence of host puparia. Male pheromone deposits were perceived by females in a still-air olfactometer at distances of up to 4.5 cm and remained attractive for at least 2 h. The function of the substrate-borne sex pheromone is discussed with respect to the mating system of N. vitripennis.
