Role of diet in host selection ofHeliothis virescens by parasitoidCampoletis sonorensis (Hymenoptera: Ichneumonidae).

Gas chromatographic analysis revealed that chemicals attractive toCampoletis sonorensis (Cameron), previously identified in cotton, were not present in wheat germ diet-rearedHeliothis virescens (F.) larvae. Diet-reared larvae fed cotton obtained the chemicals from cotton, with the consequence of enhanced kairomonal activity of the larvae and their frass toC. sonorensis. Parasitoids, presented a choice between cotton, cotton plus hosts, hosts alone, and control in an olfactometer, responded non-randomly, with the greatest number of responses to cotton plus hosts, and three times as many responses to cotton alone as to larvae alone. The role of the plant in the parasitoid-host relationship is discussed.