The face fly, Musca autumnalis, now an important pest of livestock, and sometimes of man, throughout much of the United States, has spread as far west as Washington and Oregon; and its invasion of California now appears imminent. This fly differs from its close relative the house fly, Musca domestica, in that its immature stages develop only in fresh cattle droppings, rather than in manure piles, garbage, etc. Investigations of the unique insect community of which this fly is a member indicate that the face fly may soon become established throughout much of the state. This report details movement of the fly into western states, the insect's habits, and control possibilities.

This study was supported jointly by Public Health Service Research Grant No. UI 00525 from the National Center for Urban and Industrial Health, and the Agricultural Experiment Station, University of California, Berkeley.