Q. I have noticed many small flies in the house this winter – especially near the basement and bathroom areas. How do I get rid of them?
A. We have received many samples at the extension office of small flies that have been appearing in homes this winter. In your case, it appears as if you have a phorid – or humpbacked fly. These flies are small, and they have long hind legs that they use to stabilize themselves in flight. These flies are also referred to as scuttle flies because they run about in an active erratic manner when not in flight. They have a rounded thorax which also gives them the name humpbacked fly.
These types of flies prefer moist areas in the home and use decaying, organic matter to reproduce. They sometimes can be found in drains – especially clogged drains, or areas such as a basement that might sometimes might accumulate water. Phorid flies can also be found at the bottom of trash cans, under kitchen equipment, on aging fruits, in broken sewage pipes, on medical waste and in potted plants or vases with flowers. The life cycle for most phorid flies (from egg to adult) is 2 to 4 weeks.
Finding areas where adult phorid flies lay their eggs and for larvae to develop is extremely important. Make sure to first clean your drains with appropriate cleaners and a stiff brush. Use a commercial product found at hardware stores or a 10 percent bleach solution. Don’t forget the garbage disposal and the sump pump drain. Check areas under sinks where moist, organic debris can accumulate.
All food should be refrigerated or covered. Food should not be left out for long periods of time and trash should be kept covered and removed often.
The best control for adult flies are a fly swatter or vacuum cleaner. Insect sprays are generally not recommended.
Cluster flies are also being found in homes in this area. Cluster flies are larger than house flies and are semi-dormant, flying sluggishly inside the home. Immature stages develop as a parasite of earthworms. In late summer, cluster flies seek overwintering shelter and fly to buildings in the afternoons and rest on sun-exposed areas. As the sun sets, the flies seek out cracks and other openings into the building and move to upper stories. During sunny warm days in the fall and winter, these flies become active and are found near windows or in the upper stories of homes.
The best management tactic for cluster flies is to prevent their entry into homes by caulking or filling cracks and crevices around the home.
When large numbers of flies become active during sunny days in the winter, insecticide bombs or sprays containing permethrin may be used in attics and other rooms that can be isolated from the rest of the house. The label should be consulted for re-entry times and safety information. For small numbers, you can exercise your arm once again with the fly swatter.