Do You Have Cluster Flies?

Everyone has certainly seen or heard these large, lazy, big bumbling “house fly” looking bugs that often invade homes in the fall to become annoying wintertime pests. To most people, cluster flies have no obvious characteristics that distinguish them from ordinary house flies. A cluster fly is slightly larger than a house fly, an adult can attain a length of about 3/8 of an inch. The abdomen is shiny dark and vaguely checkered with black and silver. This fly is dark gray with golden-colored hairs on its thorax. On warm days as they become active, they are particularly noticeable bouncing off windows trying to get out. Just when you think you have them under control more appear the next day. Thankfully these flies do not bite people or pets. However, they do leave dark, unsightly fecal droplets on surfaces on which they land. 

The cluster fly gets its name from the way they “cluster” together when they enter a structural void to pass the winter. During the summer cluster flies are active outdoors, where they are parasitic on certain earthworms. Adult females will deposit up to four egg clutches per year in the summer. Eggs are deposited individually in cracks in the soil approximately half an inch down. Hatching typically takes place in about three days. The young larvae move into the earthworms’ bodies. After feeding on the worms, the fly larvae pupate in the soil. The adults emerge to repeat the cycle, with up to four generations being produced each summer. In the fall the adults from the last generation will seek protected areas in which to spend the winter. They invade attics, get under siding and around windows and into crevices on the outside of buildings. They are sluggish and make little attempt to escape. On warm days in early spring they move outdoors and are often seen covering the sunny side of a house. 

Our cluster fly program includes a preventative treatment which would take place in the fall, with an outside treatment of the vertical surfaces of your structure to get the flies BEFORE they enter. Now about those flies that may have already made it in; a good attic treatment and in bad cases, usually a follow-up around the interior window casings should leave you reasonably fly free for the winter and the spring.

So this fall give us a call at 1-800-966-5568