English: Cestrotus is a genus in the family Lauxaniidae, order Diptera, the true flies. Several species occur widely in Southern Africa, where this photograph was taken. Being small and fairly cryptic, they are not well known to non-biologists, but locally some people call them "Rock Flies". A couple of dozen other species are known from Afrotropical and Asiatic regions, with several described in China. In this picture the fly is grooming; at rest it does not extend its forefeet like that.