Volatile cues from different host complexes used for host location by the generalist parasitoid Lariophagus distinguendus (Hymenoptera : Pteromalidae)

The ability of a generalist parasitoid to locate different non-related host species by volatile cues was examined in a static four chamber olfactomete r with naive females of Lariophagus distinguendus Forster (Pteromalidae), a parasitoid of beetle larvae endophytic in seeds. The following seed-host c omplexes were tested: Sitophilus granarius in rice grains, Rhyzopertha domi nica in wheat grains, and Callosobruchus maculatus in cowpeas. For comparis on the non-host Sitotroga cerealella, a moth endophytic in wheat grains, wa s used. Healthy seeds from rice, wheat, and cowpea all had an arresting eff ect on L. distinguendus. Infested seeds from the complexes rice-S. granariu s and wheat-R. dominica were significantly preferred over healthy seeds, bu t not from the complexes cowpea-C. maculatus and wheat-S. cerealella. Faece s from all beetle hosts, but not from the moth S. cerealella, had an arrest ing effect. These results indicate that L. distinguendus females innately r eact to volatile cues from different hosts and host plants. This is discuss ed with respect to current hypotheses on the use of chemical cues by genera list parasitoids.