Diagnosis. Ninth abdominal tergite divided in both sexes, forming lateral plates that may meet in the midline in the male, but are widely separated in the female. Male hypopygium with style truncate. Caudal reinforced section of spermathecal ducts of female with characteristic umbrella-like expansions (Mackerras 1956a: fig. 8G). Ocelli never fully developed. Hind tibial spurs absent. Frons generally with a callus. Flagellum of antenna compacted into a basal plate and 3 or 4 well-defined annuli (always 4 in Australian species). In wings basicosta (i.e. humeral plate) setulose or not; sc strongly setulose below on most of its length; cells R 5 and M 3 open in all Australian species; vein R 4 with or without appendix. Larvae with respiratory siphon protruding, but, in known Australian species, without stigmatal spine. Pupal synapomorphic features not yet defined.

The subfamily is divided into three tribes (Mackerras 1954), of which the Haematopotini does not occur in Australia. The other two can be distinguished by the following keys.