Cluster Flies

Biology

Cluster fly females lay their eggs in early fall near earthworm burrows. The larvae then feed on the earthworms that live underground. The larvae then cocoon before hatching into the fly.

Cluster flies derive their common name from their habit of entering a home or structure in the fall and gathering together in clusters, usually in the attic or upper regions of structures. This behavior is a good identifying feature. Cluster flies resemble house flies but are bigger and slower in their movements.

Habitat

Cluster flies can normally be found anywhere outdoors during the summer. Their migration towards shelter appears to be started by a sudden drop in temperature. The flies show characteristic behaviors; in the afternoon they settle on the upper parts of walls and on roofs, facing south or southwest, warming themselves. As the sun sets, they crawl into any opening on the exterior of any structure, but usually near the roof. For a few days, they come out during the day and return to the warmth of the structure at night.

Threats

Cluster flies are nuisance seasonal pests. When cold weather approaches, they look for protected areas for the winter. On the exterior, they gather on roofs of buildings, wall corners, cracks, crevices, or any other opening found. Once inside they may be found under clothing in closets, under curtains, behind pictures and furniture. They also may leave their hiding areas and appear on sunny warm days in winters. Cluster flies do not cause damage or bite. If crushed, they leave a greasy mark on the surface.

Habits

The flies are attracted to light and will fly towards and into lights and windows. They often drop to the floor on their backs and spin around and buzz noisily until exhausted. The annoyance of cluster flies usually begins in late summer and may continue until mid-spring. There are three to four generations of cluster flies per year. In the late summer to early fall (depending on the temperature), the adults look for sheltered areas usually in the sunny sides of buildings for the winter season.

Fly Prevention

In the summer and before late fall or early winter, seal or caulk crack, crevices, voids and all possible entry openings in and around your structure. Also, you will need to screen windows and doors.

Expert Pest Program

Expert Pest will perform a thorough treatment on the interior of your structure by a trained professional. We will locate all problem areas and properly identify the pest you are having.

All programs are specially designed to target the pest that is infesting your structure.