Abstract: Diadromus collaris is a major pupal parasitoid of PluteUa xylosteua in Hangzhou, China. This paper reports the observations of several aspects of its biology and the effect of several insecticides on its adults. At 25℃, adult females started ovipo-sition on 1-2 d after emergence and reached their oviposition peak on 3-7 d. On average, the total number of pupae parasitized by a mated female was 43.8 and the oviposition period was 11.5 d. The parasitoid had five larval instars. At 25℃, the development durations for egg and each larval instar were 1-2 d, and 5-6 d for the pupa respectively. The mean development periods from egg to adult at 15℃, 17.5℃, 20.0, 22.5℃,25.0℃, 27.5℃, 30.0℃ and 32. 5℃ were 30.6, 22.5, 17.8, 14.5, 12.1, 11.1, 10.3and 10.2 d respectively. There was no significant difference in the developmental time between male and female. The temperature threshold and the summation of effectivetemperature for the development of whole immature stage were 7.4℃ and 225.1 day degrees. A temperature range of 17℃ to 30℃ was favorable for the development, survival and reproduction of the parasitoid. The adults could be stored for 20-30 d at 15℃.Phoxim, methomyl and shachongshuang caused quick and high mortality to the adults,fenvalerate was moderately toxic, Bt, chlorfluazuron and abamectin appeared harmless to the adults.

Key words: Diadromus collaris, biology, PluteUa xylostella