Pest Control Cluster Flies

Typical Cluster Flies Scenario

A Cluster Flies morning: One crisp fall morning, you open a window to let some fresh air into your room. Suddenly, you see several hundred “dead” flies between the window and screen. While you’re staring at them, a few flies begin to move around. They’re not dead! You slam the window shut, hoping none of them get into your house! What kind of flies are these and why are there so many of them? Why are they coming back to life?

Those flies are probably Cluster flies and every autumn, they become pests of homes, schools, hospitals, and commercial buildings throughout much of the United States. Cluster fly larvae feed on a common species of earthworms during the summer. Near fall, the last summer generations of adults emerge from the soil and look for a nice, warm place to hibernate, i.e. your attic, wall voids, or window sills. These hardy little insects can travel more than a mile for a suitable overwintering site. Cluster flies overwinter and emerge in the spring to breed and lay eggs on the soil surface near the earthworms that the larvae then infest. Overwintering cluster flies are the most troublesome because of their sheer numbers. They can become active again during any warm spells in winter, and again in early spring, and try to find openings to go back outside. This results in many seeking a pest control solution.


Before cluster flies enter the structure – Structural barriers is the best method to keep cluster flies and similar pests from entering your home or office. You should make sure that all cracks around windows, doors, siding, utility pipes, behind chimneys, and underneath the fascia and other openings are sealed  should be sealed with good quality silicone caulk. Likewise, damaged screen doors and windows should be repaired or replaced.

Exterior applications of insecticides may also offer some relief from infestations where the task of completely sealing the exterior is difficult or impossible. These applications should only be applied by a licensed pest control professional. US Termite and Moisture Control can handle cluster flies and other unwanted pests call us today.

Topic: Cluster Flies