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 olfactometer with naive females of Lariophagus distinguendus Forster (Pteromalidae), a parasitoid of beetle larvae endophytic in seeds. The following seed-host complexes were tested: Sitophilus granarius in rice grains, Rhyzopertha dominica in wheat grains, and Callosobruchus maculatus in cowpeas. For comparison the non-host Sitotroga cerealella, a moth endophytic in wheat grains, was used. Healthy seeds from rice, wheat, and cowpea all had an arresting effect on L. distinguendus. Infested seeds from the complexes rice-S. granarius and wheat-R. dominica were significantly preferred over healthy seeds, but not from the complexes cowpea-C. maculatus and wheat-S. cerealella. Faeces from all beetle hosts, but not from the moth S. cerealella, had an arresting effect. These results indicate that L. distinguendus females innately react to volatile cues from different hosts and host plants. This is discussed with respect to current hypotheses on the use of chemical cues by generalist parasitoids.