Riley Pest Management
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A source for information on flies

Face Fly  Musca autumnalis

Although face flies are non-biting creatures, their feeding habits make them troubling to cattle. Face flies feed on the secretions produced by the eyes and noses of large animals. Beyond irritating cattle, this behavior also can result in the transmission of diseases. Affected animals often hide in dark places, produce less milk and lose weight. Face flies may also inflict pinkeye upon the animal and can transmit eye worms to both cattle and horses.

Face fly eggs are yellow, white or translucent in color. Each egg measures approximately three millimeters in length and 1/2-millimeter wide. Two ridges are located along their sides. When face flies enter the larval stage, they resemble yellow maggots. Adult face flies measure between six and eight millimeters in length and appear similar to house flies. Their mouthparts are commonly blunt when compared to other fly species. Both males and females have gray thoraxes with four dark brown stripes. Abdomen colors vary between genders: male face flies are brown or orange with black bases and dorsal stripes, while females are primarily black with orange bases.

Female face flies only lay their eggs in the manure of grass-fed cattle. They prefer manure that is 10 to 15 minutes old and avoid other feces. Eggs hatch within manure and larvae develop under a crust of the manure. Upon maturity, face fly larvae crawl into soil close to the manure in order to complete the pupal stage. After a week or so, adult flies emerge above the soil. Complete life cycle of face flies requires approximately two weeks.


Medium-sized flies about 1/4-inch in length.


Dark gray; four stripes are present on top of the thorax in front of the wings. Looks identical to a house fly.


This fly is very closely related to the house fly and, in fact, an entomologist is needed to distinguish between the two species. If “house flies” are suddenly appearing inside a building during the fall, winter, or spring, then face flies are likely involved. The face flies status as a pest is similar to that of the cluster fly. These flies have discovered that heated buildings are ideal for surviving the cold of winter, and the face fly is one such species. As the weather cools in late summer and early fall, the sun warms the southern and western walls of buildings. The warmth attracts these insects to buildings where they crawl inside cracks and stay there for the winter. This would be fine, but during warm winter days, some flies “wake up” and end up on the inside of the building.


Like house flies, face flies breed primarily in fresh animal manure and so are more common in buildings in rural areas near farms.


The best way to control face flies is by prevention as described below. If it’s too late and they are already inside, it takes a professional to find and treat the right areas to minimize the numbers of pests seen inside. If your building has experienced a problem in the past with face flies (or other overwintering pest species), take the following steps next summer to prevent a recurrence:

  • Seal as many cracks and holes on the outside of the building as possible, especially on the south and west walls where the sun heats the surfaces during the late summer and fall.
  • Be sure that all foundation and attic vents (if present) have tight-fitting insect screens. Plug weep holes in brick veneer buildings with small pieces of screening or wire mesh. Do not permanently seal weep holes.
  • Check the soffit vents and any gable vents or turbine vents on the roof.
  • Have your Terminix professional treat the outside west and south walls of the building near the eaves. This treatment should be completed in mid- to late August.

If flies are already inside the building, complete elimination of interior invasions is often not possible. Treatments may be applied to cracks around window frames and into cracks in walls above false ceilings, but these may not reach all the voids and spaces in which flies might be waiting out the winter. Sealing cracks around window frames is helpful in excluding flies from crawling into the building’s interior rooms.


"Riley Pest Management is a small company with a big heart that will go the extra mile to take care of an issue for you no matter when it happens. They have proven to be a very good friend to non-profits."

-- Duggan Cooley, former CEO- RCS

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