Fly-eating insects like cluster flies like to nest in walls, false ceilings, and attics. During the summer, these tiny creatures cluster together on the warm side of the wall. When the temperature drops, they seek shelter in a sheltered location, such as a crack or window pulley hole. They can also enter through baseboards and other small openings around windows.
When flies enter your home through the exterior, they don’t often become a major problem. However, if they enter your house through the interior, they may become an annoyance. In order to prevent them from reproducing in your home, you need to seal up any cracks and holes. Cluster flies tend to be less of an issue in homes that are tightly weather-sealed and have good insect screens.
Another way to control flies in your house is to apply a chemical fly repellent. You can use either malathion or diazinon spray to spray surfaces in your basement, attic, and closets. You can also spray the exterior of your home with these pesticides in fall.
If cluster flies have inhabited your home, it’s likely they’ll return each year. Since they like to be in areas with bright lights, cluster flies may be a nuisance.