The Diapriidae

gaster with only 4 clearly defined segments posterior to the large tergite; petiole at apex beneath without suck a pencil of hairs; flagellum 1 without trace of a basal modification amd evenly hairy all round. (radial cell completely closed)

gaster with 6 clearly segments posterior to the large tergite; petiole beneath without such a pencil of hairs; flagellum with at least a straight-edged basal modification from which, in profile, no hairs arise