The Fanniidae are a small (285 species in five genera) group of true flies largely confined to the Holarctic and temperate Neotropical realms; there are 11 Afrotropical species, 29 Oriental, and 14 Australasian.

Adults are medium-sized to small and usually have mainly dark body and leg colours. Males congregate in characteristic dancing swarms beneath trees; females are more retiring in habit. Larvae are characterised by their