Trixoscelididae Hendel, 1916

Minute to small (1.5-3.5 mm), rather stout, usually dark flies with densely microtomentose body (or at least thorax). Head rounded; its chaetotaxy characterised by the absence of interfrontal setulae, by the ocellar setae arising outside the ocellar triangle, and by the two fronto-orbital setae. Prosternum setulose;  proepimeral (propleural) setulae generally absent. Thoracic setae rich, usually with five dorsocentral setae. Wing often with infuscated patterns. Costa strongly spinulose, with subcostal break; subcosta complete, ending near R1, cell bm closed, cell cup short. All tibiae with dorsal preapical setae. Male genitalia with small cerci, distinctive gonostyli, short hypandrium, large phallophore and complex distiphallus; epiphallus absent. Female postabdomen with 7th tergum and sternum fused or closely attached, 8th sternum with lateral setulose lobes, and with 3 (2+1) spermathecae. The unknown larvae are probably saprophagous; two Trixoscelis species have been reared from a blackbird's nest. Trixoscelis species are thermophilous and adults can be swept from vegetation in warm, sandy, steppe and forest steppe habitats.

The family has often been considered, even recently, as a tribe or subfamily of the Heleomyzidae, but it is here ranked as a family following the Fauna Europaea (Woźnica 2007). Altogether 26 species belonging to the sole European genus Trixoscelis Rondani, 1856 have been recorded in Europe and adjacent areas as included in the Fauna Europaea (Woźnica 2007, 2008); five are listed in the present checklist: five in the Czech Republic (four in Bohemia, five in Moravia), and four in Slovakia. Since the ECV1, the numbers of species in the Czech Republic (both in Bohemia and in Moravia) and Slovakia have not been changed. The family was treated by Papp (1998) within the framework of the “Heleomyzoid families”, which included a key to the three Palaearctic genera. There is no identification tool for the European species of Trixoscelis; the species occurring in Central Europe can be identified with the keys in Hackman (1970) and Soós (1981) with corrections presented by Woźnica (2008). The family has received little attention in the Czech Republic and Slovakia; references to the scattered previous records can be found in Roháček and Barták (2001) and Roháček et al. (2005). The nomenclature of this checklist follows that in the Fauna Europaea (Woźnica 2007) and Woźnica (2008).