March 1, 2021 / New England Pest Control

Why You May Have Flies in the Wintertime

Why You May Have Flies in the Wintertime

Where there are horses there are often horseflies, and where you find fruit you’ll usually find fruit flies, so what kind of “cluster” attracts cluster flies and why do some people find them indoors so much during the winter?

The “cluster” in “cluster flies” actually describes their behavior, not what attracts them. They tend to gather in large numbers near windows, often in rooms you might seldom use.

In fact, one of the toughest things about dealing with cluster flies is that they aren’t particularly attracted to anything you can dispose of or clean out.

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They’re Easy to Remove, but Impossible to Evict

Although they are sluggish and easy to swat away or vacuum up, once cluster flies have settled in your home for the winter, they’re almost impossible to get rid of. The 1/2-inch or so, dull grayish-brown flies become more active as temperatures rise, becoming so frisky in the springtime that they’ll start trying to get out of your house, so you may notice them more.

That means, of course, that the opposite is also true -- in the fall, as outdoor temperatures drop, cluster flies are driven indoors in search of warmth. Since you probably don’t want to deprive yourself of heat during the winter, your best bet for dealing with cluster flies begins before the cold season starts.

The Only Thing They Kill is Time

Once cluster flies have settled into your home for the winter, they don’t need much. They’re not there to breed or eat, so there isn’t much you can do to persuade them to leave. There are, however, preventative measures you can take to help guard against them next year.

On the one hand, that can be frustrating. At least with fruit flies and other “trash” flies you can clean up messes and seal up any food sources that could be attracting them. But on the other hand, at least cluster flies are more of an annoyance than anything, since they pose no particular threat to human health or safety.

An Ounce of Prevention...

Every August, we offer our Fall Invader Program, which targets cluster flies along with other pests like stink bugs and Asian lady beetles. One important step to keep these and other fall invaders out of your house is to put a seal around your home well before the temperature drops.

Another reason an ounce of prevention is worth a pound of cure: before spring comes, many of them will die within your walls, which can then attract secondary pests like beetles or rodents who come looking to scarf up the dead fly carcasses. That’s why we embrace a holistic approach known as Integrated Pest Management (or IPM for short), which prioritizes preventative and nontoxic methods of pest control over chemicals. Another benefit, of course, is that the fewer pesticides we use, the safer your environment is for your family and pets. 


Make sure your home is ready to combat cluster flies this year. Give us a call for a free quote, and to be put on the list for a Fall Invader service to keep them out next winter.

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