THE INFLUENCE OF PLANT-SPECIES ON ATTRACTION AND HOST ACCEPTANCE IN COTESIA-GLOMERATA (HYMENOPTERA, BRACONIDAE)

Females of the larval parasitoid Cotesia glomerata (L.) use plant-asso ciated cues to locate their lepidopteran host, Pieris rapae L. In this study we investigated the influence of four-host plant species, Brass ica oleracea var. acephala ('Vates' kale), Tropaeolum majus (nasturtiu m), Lunaria annua (honesty), and Cleome spinosa (spider flower), on tw o components of the host selection process in C. glomerata, namely, at traction and host acceptance. Choice tests in a flight tunnel showed t hat parasitoids were attracted to some host plant species more than to others in the absence of host larvae. B. oleracea was the most attrac tive plant species, followed by L. annua, T. majus, and C. spinosa. In previous studies it was shown that B. oleracea carries highly suitabl e hosts for C. glomerata and that, in the field, parasitization rates on this plant were the highest. When host larvae were reared on the fo ur host plant species and then transferred to a common substrate (B. o leracea var. capitata, cabbage), plant species that had sewed as diet for the hosts did not have a significant effect on acceptance for para sitization. Thus, parasitoids were attracted to host plant species dif ferentially, but they did not discriminate among host larvae based on the dietary history of their hosts. For C. glomerata, it appears that phytochemistry mediates host selection more by influencing parasitoid attraction than it does by affecting host acceptance.