none Chilo infuscatellus; Chilo partellus; FOOD-PLANTS; Maize & sugarcane; Plant preference of hymenopteran parasite; HYMENOPTERAN-PARASITES; Cotesia flavipes; Plant preference studies Cotesia flavipes; LEPIDOPTERAN-HOSTS; Chilo infuscatellus & C partellus; Plant preference studies Cotesia flavipes is an important parasitoid of graminaceous stalk borers in South East Asia. It has been successfully introduced in a number of countries. In Pakistan it became established on maize borer, Chilo partellus following its introduction from Japan in 1972 but seldom attacked sugarcane borers. Different strains of this species have preference for different hosts and host plants. In the laboratory its host plant preference changed from sugarcane to maize when reared on sugarcane borers Chilo infuscatellus fed on sugarcane for 5 successive generations. The preference changed from sugarcane to maize in five generations again when the sugarcane adapted strain was reared on C. partellus fed on maize.