Cluster flies and house flies have common characteristics and are often mistaken for one another. Many people don’t even know what a cluster fly is. If you’re seeing flies in your home, there are a few ways you can determine which fly you are dealing with.

Characteristics: The cluster fly averages between 1/4 to 3/8 inch long. They are dark gray, never metallic blue or green. When crushed, they give off an odor like buckwheat honey. Cluster flies closely resemble house flies, but they are usually larger and have a yellowish sheen on the thorax. They move slowly. They gather in large numbers, particularly around windows.

About Cluster Flies: Cluster flies are flies of the genus Pollenia in the family Polleniidae. Unlike the more familiar blow flies, such as the bluebottle genus Phormia, they are completely harmless to human health because they do not lay eggs in human food. Cluster flies are outdoor insects that lay their eggs in soil in the summer months. The larvae then hatch and feed on earthworms. They start to seek refuge in your home late in the fall to overwinter. When cluster flies find a safe and warm location, they release a pheromone that attracts other flies to the area. This results in large numbers of cluster flies gathering near or in your home. Though they are inactive in the winter, they will emerge when temperatures rise.

What are they attracted to? Cluster flies are attracted to light, which explains their fixation with windows on sunny days. They are also attracted to artificial lights at night. These flies are not attracted to garbage and other refuse like so many other types of filth flies.

When to treat– end of summer or early fall before temperature drops.

Prevention is the best measure to keep away Cluster Flies. Seal any cracks or crevices along doors and windows, vents, and along the roof. Patch any damaged screens. Fall months are the times to use a good residual spray before they enter the building and over-winter. Spray the outside walls of the building where cluster flies are likely to land and rest before entering the building.

Give us a call today for your free inspection and a quote on an affordable treatment plan. Don’t worry if you already have an infestation. We can treat the areas in and around your home now and (this is important) come back in the late summer/ early fall to help prevent future infestations.