Cluster Flies

no-cluster-fliesHave Cluster Flies?

The cluster fly is a pest in homes, schools, and commercial buildings throughout much of New York and surrounding states from late summer until spring.

Treatment: Odorless One Time Application! We begin our treatment starting August 1.

GreenWay will spray the exterior of the dwelling with emphasis to soffits, around window frames, and under siding where they can enter.  Since cluster flies hibernate in inaccessible areas, the use of pesticides inside is generally unsuccessful.  Effective control barrier to the exterior is best for fly treatments.

What is a Cluster Fly?

Some are smaller but most are slightly larger than the common house fly.  They are non-metallic in color and light with dark gray areas on the abdomen.


Heat produced by the sun on the roof or walls, or warmth resulting from the heating system may cause them to abandon hibernation sites and become active.  They are generally not attracted to food indoors, but attempt to escape by going to lights or windows.  Cluster flies will try to escape until they are exhausted.  As adults, and in spring on warm days those spending the winter indoors emerge from hibernation to breed and lay eggs on the surface of the soil of lawns and fields in rural farm areas.  Larvae hatch from the eggs and attack earthworms in the soil.  After about a month, pupae are formed near the surface.  In just a few days, the adults emerge, breed and lay eggs to begin another generation.

During the summer, 3-4 generations can be produced.  Each adult female may lay several hundred eggs.  Flies emerging from the soil continue to enter dwellings until heavy frost.  Efforts to control cluster flies in lawns and gardens are usually not successful because they can fly for considerable distances and can come from anywhere.


Adult cluster flies accumulate in clusters in attics, between walls and other voids.  Screens offer no protection.