Aphelinidae is a moderate-sized family of tiny parasitic wasps, with some 1160 described species in some 35 genera. These minute insects are challenging to study as they deteriorate rapidly after death unless extreme care is taken (e.g., preservation in ethanol), making identification of most museum specimens difficult. The larvae of the majority are primary parasitoids on Hemiptera, though other hosts are attacked, and details of the life history can be variable (e.g., some attack eggs, some attack pupae, and others are hyperparasites). They are found throughout the world in virtually all habitats, and are extremely important as biological control agents.
They are difficult to separate from other Chalcidoidea except by subtle features of the wing venation and other difficult characters, and it appears the family is paraphyletic, and therefore likely to be split up in the future (e.g., the Azotinae and Calesinae may become separate families).