If there was ever a pest that made you feel like you are living in the Amityville Horror it is cluster flies. They invade your home by the hundreds or thousands causing even the most battle tested person to freak out. They are also mistaken for Bottle flies as people think something must have died if I have this many flies.
Adult cluster flies resemble house flies, but are slightly larger, about 5/16 inch long, narrower and nonmetallic gray. Their wings overlap when they are resting.
Cluster flies are found in homes, churches, hospitals, apartment complexes, commercial and public buildings and other structures. These large, sluggish flies appear on warm, sunny days during late autumn, winter and early spring. They occur in large numbers, especially at windows and in rooms not frequently used. They can be found in large numbers in attics and on window sills in basements. They make irritating, buzzing noises, spin around and move sluggishly.
Unfortunately cluster flies are a real freak of nature or natural phenomenon that is very common in the New England region. WHY? To eliminate cluster flies you would need to eliminate earth worms & that is an impossible task! Female cluster flies lay eggs singly in soil cracks and crevices in the soil then penetrate and develop in the bodies of earthworms. Adult cluster flies move to protected places to hibernate AKA over-winter in late August and early September. The flies “cluster” on the sunny side of buildings, typically during the day. As the sun sets and temperatures drop, flies crawl into the building through cracks, especially under eaves, gaps in siding, unscreened vents, etc. They look to over-winter in structures until they exit on warm days in the spring. The process is repeated year after year.
However drastic temperature changes in the winter may force activity inside structures. Historically very wet spring & summer seasons usually indicate heavy cluster fly activity.
What can be done to control them? The goal is suppression Vs elimination, you must have a tolerance for these pests. An exterior treatment by EHS in the fall can provide some relief. The key control measure is structural exclusion of any possible voids from the roof to the ground with particular emphasis on the sunny side of the structure. If you see flies inside it is best to just vacuum them up & dispose of them. Call EHS at 877-507-0698 or email us at email@example.com, as we can tailor a program for your specific needs.