In Oconee County, S.C., a dump fly,Ophyra aenescens(Wiedemann), displaced the house fly,Musca domesticaL., as the predominant muscoid fly present in the pits of two enclosed environmental poultry houses. During an 18-wk period (June–October 1983), these flies were allowed to breed without restriction. Twenty-eight sticky-tape monitoring stations at distances of 0–1,500 m from the poultry farm provided evidence that flies did not migrate to sensitive areas such as nearby residences in sufficient numbers to be considered a nuisance. Habits of this muscoid fly differ from those of the house fly in thatO. aenescensapparently is more attracted to the dark pit area of poultry houses, shaded woodlands, and similar areas rather than human habitations. Because it does not appear to be a problem at human habitations,O. aenescensmay be useful as an alternative biological strategy for suppressing house-fly breeding on poultry farms.