GENERALIST AND SPECIALIST PARASITOID STRATEGIES OF USING ODORS OF ADULT DROSOPHILID FLIES WHEN SEARCHING FOR LARVAL HOSTS

Parasitoids foraging for larvae of Diosophila flies can use odours of adults of their hosts as well as odours of the food of their host larv ae. Adult Drosophila deposit volatile aggregation pheromones into a su bstrate when mating and ovipositing. In this paper three species of pa rasitoids with different degrees of host specialization are compared i n bioassays with regard to innate responses to aggregation pheromones of adult drosophilid hosts. Specialist parasitoids are assumed to use more specific information about their hosts than generalist parasitoid s. Two phylogenetically related eucoilid parasitoids, Leptopilina boul ardi a host specialist, and L. heterotoma a generalist, were attracted to odours of adult hosts in windtunnel tests. L. heterotoma responded to odours of all species within its host range and one non-host. The specialist L. boulardi was attracted to odours of adult hosts within i ts range but also to some non-host species. Production of similar pher omonal compounds by non-host and host Drosophila species can explain t he reponses by L. heterotoma and L. boulardi to non-host species. A ph ylogenetically unrelated braconid host specialist Asobara tabida did n ot respond to any odours of adult hosts. However, when A. tabida femal es were given an oviposition experience in the presence of host pherom ones, they became attracted to aggregation pheromones of their host.