Cluster or Attic Fly Facts & Information

What Orkin Does

Your local Orkin Pro is trained to help manage cluster fly infestations and similar pests. Since every building or home is different, your Orkin Pro will design a unique fly treatment program for your situation.

Orkin can provide the right solution to keep cluster flies in their place...out of your home, or business.

What do cluster flies look like?

Cluster flies, also known as attic flies, are household pests.

• Length: Adults measure 8 to 10 millimeters.

• Body: Light and dark gray-checkered abdomens. The thorax of an adult cluster fly is covered in short, golden hairs and the wings overlap when at rest.

• Characteristics: Cluster flies are slightly larger and darker than the common housefly and move more sluggishly.

Cluster Fly Life Cycle

The life cycle of the cluster fly (Polenia rudis) begins in the spring when they leave the overwintering sites (attics and wall voids of houses) and lay their eggs in the soil. The larval or maggot stages of this fly attack and eat earthworms. Cluster flies' development time from egg to adult is about 27 to 39 days.

There are several generations of cluster flies during the summer. Each time the female returns to lay eggs in the soil. However, the flies of the last generation (mid to late August) will spend the winter in a protected location, and start the life cycle over again in the following spring.

Cluster flies begin searching for a place to spend the winter during the last month of summer, usually in late August and early September. They will gather on the sides of houses that are warmed by the afternoon sun. They collect there by the hundreds or thousands. Some of the flies find openings and make their way inside the house. They spend the winter inactive until the temperature goes up.

What do cluster flies eat?

Cluster fly larvae feed on earthworm hosts for several days, at which time they molt and pupate in the soil.