BIONOMICS OF THE FACE FLY, MUSCA-AUTUMNALIS

The face fly was introduced from the Palearctic region and spread acro ss North America in 20 years after World War II. Adults feed on cattle and horses, and larvae develop in fresh cattle dung. Little genetic d ifferentiation appears between European and North American populations and among regions within North America. After an autumnally initiated diapause, overwintered flies emerge in spring and reproduce through l ate spring and summer. Generations after the first overlap, and age st ructure develops toward a stable age distribution. After three to ten generations, depending on weather, facultative diapause interrupts hos t feeding and oogenesis, and flies with hypertrophied fat body enter o verwintering hibernaculae. Life table statistics and factors affecting population growth and diapause are reviewed. Early views on the fly's effects on animal productivity may have been exaggerated. On-farm con trol by conventional means has not been effective because of the fly's population dynamics and mobility. We suggest that the alternatives of classical biological control and area-wide control with the sterile i nsect technique should be considered.