Many Sepsidae have a curious wing-waving habit made more apparent by dark patches at the wing end.

Adult flies are found mostly on mammal excrement, including that of humans (less often on other rotting organic matter), where eggs are laid and larvae develop, and on nearby vegetation, carrion, fermenting tree sap, and shrubs and herbs.

Many Sepsidae apparently play an important biological role as decomposers of mammal and other animal excrement.

Sepsids have one or more bristles at the posteroventral margin of the posterior spiracle of the thorax, a character that distinguishes the family from other acalyptrates.

The larva is slender, tapering at the front end, and smooth except for ventral creeping welts.