Cluster Flies

The cluster fly close up

You’re probably accustomed to smacking houseflies with a fly swatter or a rolled up newspaper (or if you’re taking the more humane route—trying to shoo them out the door) in the summer.  But did you know there’s another type of invading house fly, cluster flies, that emerge in the colder months and tries to get comfortable inside your home?

While cluster flies, or pollenia rudis, are often confused with the more common house fly, there are a few ways to tell them apart. Cluster flies are slightly larger, and instead of all black or metallic blue, they are a dull gray color with black markings. They also have tiny yellow hairs on their body, sometimes giving the illusion of a golden glow.

Cluster flies debut in the autumn months, and normally fly to the sunny-side of homes and other structures in the search for an overwintering site. They crawl deep into protective cracks or wall voids, and if we experience a warmer day in the winter, the flies get confused and become active again.

Cluster flies are nuisance pests and while they won’t damage your home’s structural integrity, they could leave spots of dark-colored fly poo on your walls–yuck!  


It’s important to consider protecting your home against cluster flies before they become a problem, as once they get inside, they can be hard to get out. Seal any cracks in and around your home with silicone or silicone-latex caulk. Check doors, siding, around utility pipes, underneath the fascia, and repair or replace any broken window or door screens.  You can also apply an insecticide to the exterior in late August or early September, before the flies have begun the overwintering process.

If cluster flies have already gotten into your home, use a vacuum to remove any that you can see, or consider an insecticide that’s safe for indoor use.

If you need help dealing with your cluster fly problem, feel free to give us a call.

Scroll to Top