DIURNAL FLIGHT ACTIVITY OF DIADEGMA INSULARE (HYMENOPTERA, ICHNEUMONIDAE), A PARASITOID OF THE DIAMONDBACK-MOTH (LEPIDOPTERA, PLUTELLIDAE),IN THE FIELD

We studied the diurnal night activity of Diadegma insulare (Cresson) a t the Collins Road Entomology Research Farm Michigan State University during the summers of 1992 and 1993. Foraging activity was measured us ing sticky traps placed within the broccoli canopy and by direct visua l observation. might activity of D. insulare males was positively corr elated with light intensity, whereas activity of females was positivel y correlated with light intensity, temperature, and wind speed. Relati ve humidity, percentage cloud cover, and time of day did not influence D. insulare catch. There was no significant difference between male a nd female catch. The patterns of males' and females' flight activity t hroughout the day were significantly different front a uniform distrib ution except on ii and 22 August 1993 for males and 14 August for fema les. Activity generally began between 0800 and 1000 hours, peaked betw een 1100 to 1300 hours, and stopped by 2100 hours. There was no signif icant correlation between the numbers of males and females caught on t he same trap ap, suggesting that an increase in numbers of females doe s not attract more males. Males were caught more Frequently than femal es in September of both years, suggesting that males were more abundan t or active at the end of the season. The total numbers caught (both s exes) at different times of the day in sticky traps were generally pro portional to the numbers of parasitoid visually observed. The numbers of D. insulare caught were positively correlated with the numbers of d iamondback moth larvae per plant. This information could be useful for developing a model that can predict the peak diurnal activity of D. i nsulare in the field which would help with decisions on whether pestic ides should be sprayed.