Feeding by a number of non-biting muscid species on blood made available by biting flies is known to occur in the Old World (Hammer, 1941; West, 1951). Species in several genera are involved, but particularly Musca. In North America, Hydrotaea tuberculata Rondani has been observed feeding in association with horse flies and stable flies (Tashiro and Schwardt, 1953). Often in these feeding associations, flies of the non-biting species not only visit abandoned wounds, but also wait near a feeding fly or attempt to feed simultaneously with it.