Plutella xylostella; HYMENOPTERAN-PARASITES; Diadegma insulare; Parasitoid diurnal flight activity; POPULATION-DENSITY; Hymenopteran parasitoid diurnal flight activity relations; WASHINGTON-; East Lansing; Hymenopteran parasitoid diurnal flight activity, influences Diadegma insulare; DIURNAL-ACTIVITY; Flight activity; LEPIDOPTERAN-HOSTS; Plutella xylostella; Parasitoid diurnal flight activity, Washington; CLIMATE-AND-WEATHER; Diurnal flight activity relations; MICHIGAN-; East Lansing; Diurnal flight activity, influences, parasitoid of Lepidoptera We studied the diurnal flight activity of Diadegma insulare (Cresson) at the Collins Road Entomology Research Farm Michigan State University during the summers of 1992 and 1993. Foraging activity was measured using sticky traps placed within the broccoli canopy and by direct visual observation. Flight activity of D. insulare males was positively correlated with light intensity, whereas activity of females was positively correlated with light intensity, temperature, and wind speed. Relative humidity, percentage cloud cover, and time of day did not influence D. insulare catch. There was no significant difference between male and female catch. The patterns of males' and females' flight activity throughout the day were significantly different from a uniform distribution except on 14 and 22 August 1993 for males and 14 August for females. Activity generally began between 0800 and 1000 hours, peaked between 1100 to 1300 hours, and stopped by 2100 hours. There was no significant correlation between the numbers of males and females caught on the same trap, suggesting that an increase in numbers of females does not attract more males. Males were caught more frequently than females in September of both years, suggesting that males were more abundant or active at the end of the season. The total numbers caught (both sexes) at different times of the day in sticky traps were generally proportional to the numbers of parasitoid visually observed. The numbers of D. insulare caught were positively correlated with the numbers of diamondback moth larvae per plant. This information could be useful for developing a model that can predict the peak diurnal activity of D. insulare in the field which would help. with decisions on whether pesticides should be sprayed. none