Face Fly

Musca autumnalis De Geer (family Muscidae) is a non-biting fly, closely related to the house fly, typically measuring 6-8 mm in length. Adults are dull gray with four dark stripes on the thorax; males have eyes that nearly touch, while females have widely separated eyes. Eggs are laid exclusively on fresh (within 15 minutes of defecation) bovine manure. Larvae, which are creamy white maggots, develop within the manure, feeding on microorganisms. The lifecycle from egg to adult can be as short as 10-20 days, depending on temperature, allowing for multiple generations per season.

Adult face flies primarily feed on animal secretions (mucus, tears, saliva), nectar, and dung liquids. They are strongly attracted to the faces of cattle and horses, clustering around the eyes, nose, and mouth to feed, causing annoyance and potentially vectoring pathogens such as Moraxella bovis (cause of pinkeye). They overwinter as adults in sheltered locations like attics, barns, and wall voids, emerging in spring to seek host animals. They are strong fliers and can travel several miles.