The Diapriidae

marginalis distinctly longer than its distance from the basalis (Small species, ca. 2.5mm.; radial cell either open or closed but its length when closed, or as indicated by the incomplete radialis, at most but slightly greater than the length of the marginalis; seventh and eight gastral segments not clearly separated and together forming a smooth, narrow, downcurved, almost hairless segment which is closely ensheathed by the hypopygium; large sternite never humped at base (cf. Psilomma))

marginalis rarely nearly equal to its distance from the basalis and then it is much shorter than the radial cell or the radialis is virtually wanting and the large sternite is humped at base