Effect of leaf age on the flight response of a parasitic wasp, Cotesia kariyai, to a plant-herbivore complex was studied in a wind tunnel. Both young and old leaves infested with host larvae (common armyworms: Mythimna separata) attracted more wasps than their respective uninfested leaves. Preference of the wasps to uninfested young leaves vs. uninfested old leaves was not significantly different in choice experiments. However, when young infested leaves were compared against old infested leaves in choice experiments, the wasps showed a significant preference for the former. In the single stand experiments, % landing response to young infested leaves was not significantly different from the old infested leaves. The fact that attractiveness of infested corn leaves to wasps differs according to leaf age suggests differential allocation of induced indirect defense in the corn plant. Mythimna separata (Noctuidae) : Host Cotesia kariyai (Braconidae) : Parasite Nutrition; Diet; Behaviour; Orientation; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts Cotesia kariyai; Taxis; Lepidopteran hosts; Leaf age effect on flight response to host-plant complex; Mythimna separata Mythimna separata; Food plants; Zea mays; Hymenopteran parasites; Leaf age effect on parasite flight response to host-plant complex; Cotesia kariyai none