The Pesky Flies of Fall
As summer comes to an end, you might be surprised to hear the annoying buzz of flies gathering in your windows and circling your lights. They’re not the last surviving houseflies of the year – they’re most likely the earliest invading cluster flies of fall, and they can be a major annoyance that lasts all through the colder months.
Cluster flies live relatively long lives for flies, reproducing in three to four cycles throughout spring and summer so that there are quite a few of them by the time fall rolls around. These flies “cluster” together in large numbers to overwinter as temperatures cool. They crawl into buildings and homes through gaps around windows, baseboards and loose-fitting siding. Cluster flies are attracted to warm, sunny places in upper stories of buildings, and they’re found quite commonly gathered around upstairs windows or along south-facing attic walls. They’re typically described as clumsy because they buzz incessantly around lights and windows, frequently colliding with objects and dropping onto the floor on their backs. Although cluster flies don’t pose a health hazard in the same way that houseflies do or cause any property damage, they can attract secondary pests like spiders and beetles in large numbers.
If you live in an area where earthworms are abundant, chances are that you have had problems with cluster flies in the past: Cluster flies are parasitic insects that feed on and actually develop inside earthworms. You’re also more likely to attract cluster flies if you have little shade around your home because the flies are drawn to sunny outside walls. If you have had problems with cool-weather nuisance flies in the past, you can help prevent future infestations by using caulking to seal openings or cracks high up on your home, such as on fascia, dormers, vents and flashing.
Keep an aerosol spray, such as Black Flag® Flying Insect Killer, on hand to take care of flying insects throughout fall and winter. Just spray affected rooms upward toward the center. Insecticide-free options, like the Black Flag® Window Fly Trap, are also very effective for cluster fly control. The sticky film adheres directly to windows to trap cluster flies and other flying insects for several months.