The traditional taxonomic system treated the families Scelionidae and Platygastridae separately under the superfamily Platygastroidea. However, most authors now recognize only the Platygastridae after molecular studies showed that the traditional system was polyphyletic.
Most species are egg parasitoids of Lepidoptera, Hemiptera and Orthoptera. This includes all genera previously under the Scelionidae, while many platygastrids (Platygastridae in the traditional sense) oviposit either in eggs or early larvae of gall midges (Cecidomyiidae) and complete their development in the larvae. The adults are in general small (0.6 to 10 mm), black and have elbowed antennae.
The following genera are currently entered under this family: