During studies of the parasite complex of the diamondback moth, Plutella maculipennis Curt., at Ottawa, Ontario, July to October, 1952, and April, 1953, 1,234 host cocoons were collected from a heavily infested field of Penn State Ballhead cabbage. On October 31, eight adults (2 ♂ and 6 ♀) of Tetrastichus sokolowskii Kurdj., emerged from a single cocoon collected 16 days previously and held under laboratory conditions in a gelatin capsule. On May 10, nine adults (1 ♂ and 8 ♀) and on May 15, eight adults (1 ♂ and 7 ♀) of the same species emerged from two overwintered cocoons collected 14 and 16 days previously. In each case, the lack of parasitic remnants indicated that they were primary parasites.