Members of the present genus are commonly encountered in faunistic studies of the southwestern United States and Mexico, but little or no informati,on has been recorded concerning their biology or ,host relationships and taxonomic status.

Brauer and Bergenstamm established Mochlosoma with validum, new, as the type and sole original species, (Zweifl. d. Kaiserl. Mus., IV, 1889, 126). The type series is in the Vienna Natural History Museum, and apparently it was not seen by any American worker in Diptera until 1925, when Aldrich recharacterized the genotype and restricted the type series to the single male specimen from Pennsylvania, (Ann. Ent. Soc. Amer., XVIII, 116-118). More recently Townsend also redefined the genus (Manual of Myiology, part VII, 1938, 346-347). These interpretations of the generic characters are now generally accepted for Mochlosoma and are summarized for ready reference to all species included in the accompanying key.