Ostrinia nubilalis; HYMENOPTERAN-PARASITES; Eriborus terebrans; Diurnal behaviour of parasite under seminatural conditions; MICHIGAN-; Diurnal behaviour of hymenopteran parasite under seminatural conditions Eriborus terebrans; FEEDING-BEHAVIOUR; DRINKING-; EGG-LAYING; MATING-; GROOMING-; Preening; DIURNAL-ACTIVITY; Seminatural conditions; RESTING-; LEPIDOPTERAN-HOSTS; Ostrinia nubilalis; Diurnal behaviour of parasite under seminatural conditions; MICHIGAN-; Diurnal behaviour under seminatural conditions, lepidopteran host Unmated pairs of Eriborus terebrans (Gravenhorst), a parasitoid of the European corn borer, Ostrinia nubilalis (Hubner) (Lepidoptera: Pyralidae), were confined in flight cages provisioned with food, water, and corn plants infested with O. nubilalis. Individuals were observed hourly from before sunrise until after sunset for 3 d to assess diurnal patterns of behavior. Observed behaviors were assigned to 13 categories including resting, preening, walking, flying, feeding and drinking, mating, host searching, and ovipositing. Resting and preening accounted for the majority of observations. Drinking and feeding occupied only a small proportion of the total as did host searching and ovipositing. E. terebrans followed consistent daily patterns of activity. Before sunrise, wasps were quiescent and exhibited a characteristic body and antenna posture (inactive rest). For both males and females, walking and flying peaked between 0900 and 1100 hours eastern standard time. Host search by females peaked at 0900 hours. During the afternoon, both male and female activity declined. Inactive rest reached a high at 1300 hours, decreased somewhat until 1500 or 1600 hours, then increased as all wasps returned to inactive rest by sunset. Wasps were significantly more active on hotter than on cooler afternoons. none