Microplitis demolitor Wilkinson was collected in Queensland, Australia, and imported into the United States, where laboratory studies were conducted to determine its life history, host range, and other aspects of its biology. In all but 3 of 10 lepidopterous hosts tested, oviposition was attempted by M. demolitor , although only Heliothis zea (Boddie), H. virescens (F.), and Pseudoplusia includens (Walker) were suitable hosts for parasitoid development. A low number of parasitoids successfully developed from Trichoplusia ni (Huebner). Parasitoid developement time from egg to pupation was ca. 8 days, and from pupation to adult emergence was 5 days at 27 degree C. Longevity of M. demolitor males and females was ca. 8 days.