Influence of pre-emergence experience on response to host and host plant odours in the larval parasitoidEupelmus vuilleti

The response to different host and plant species odours was investigated inEupelmus vuilleti (Crw). This hymenopteran is a solitary ectoparasitoid of several species of bruchids developing inside Leguminosae seeds. The locomotor behaviour of females reared onBruchidius atrolineatus (Pic) larvae developing inVigna unguiculata (Walp) seeds was analysed using a tubular olfactometer. Females showed a specific sensitivity to the semiochemicals emanating from the host and the seed species on which they had developed. Odours fromV. unguiculata seeds were attractive to the parasitoid and stimulated their locomotor activity. Odours fromVigna radiata (Wil) seeds had no effect on the locomotor behaviour. Odours fromB. atrolineatus larvae were attractive to the females whereas odours fromCallosobruchus maculatus (Fab), another bruchid species, had no effect. By isolating the females from the seed and the host at different developmental stages, we found that the specific sensitivity observed resulted from an early adult learning. This learning which occurs before the emergence from the seed while the imago is in the larval chamber of its host is dependent on contact with the seed and the host larval remains.