The Myidae (alternative spelling Mydaidae), or Mydas flies, are a small (fewer than 400 species), cosmopolitan family of rather large flies - including, in fact, the largest known fly, Gauromydas heros (a.k.a. Mydas heros). Many of the species, in addition to their large size, are mimics of stinging Hymenopterans, especially wasps. They are most diverse and abundant in arid regions of the world, but can be found in other habitats. They are infrequently encountered as the adult life span appears quite short, and little is known about their biology, though larvae of some species appear to be subterranean predators of ants.