Small to moderate-sized flies, length 1-11 mm, usually dull and dark coloured, but unusually diverse in body structure, vestiture, and ornamentation, making this family difficult to characterize; female usually larger than male. Pseudopostocellar setae divergent or lacking. Arista bare, pubescent, or pectinate; aristal rays on dorsum only, except in Asmeringa Becker and in some Ptilomyia Coquillett. Wing with humeral and subcostal breaks; Sc vein rudimentary; vein R1 merging with C before middle of wing; cells bm and dm not separated by a crossvein; Cell cup absent. Anepisternum setulose. Preapical dorsal seta lacking on fore and hind tibiae.