08/24/2026
Cluster fly season will be here before you know it.
As we move toward late summer and fall, cluster flies start looking for warm, protected places to spend the winter. Your home can be the perfect place.
They can get into wall voids, attics and other protected areas through small openings around windows, doors, siding, soffits and other parts of the exterior. Once they're inside, you may not notice them right away. Then, when we get those warm and sunny days, they can become active and start appearing around your windows and throughout the house. If you've dealt with cluster flies in previous years, there's a good chance they'll try to come back.
A few things to watch for:
• Flies gathering around sunny windows
• Flies appearing inside during warm fall or winter days
• Previous cluster fly problems returning year after year
• Gaps or openings around windows, doors, soffits and exterior areas of your home
Cluster flies are not the same as house flies, and they do not reproduce inside your home. They are looking for a place to shelter from the cold.
Here's something a lot of homeowners don't realize: the flies you see in the spring are generally the ones that made their way into your home the previous fall. They spend the fall and winter sheltered inside and then become active again when temperatures start to warm up. By spring, they're nearing the end of their adult life cycle.
That's why fall is the ideal time to get ahead of a cluster fly problem. Treating in late summer through mid-fall gives you the best opportunity to deal with them before they make their way inside to overwinter.
A proper treatment focuses on the areas where cluster flies are most likely to get in and shelter, including around eavestroughs, soffits, doors, windows, brick and siding. Interior areas can also be treated where appropriate, and if the attic is accessible, it's an important area to check and treat since cluster flies commonly overwinter there.
Have you noticed cluster flies coming back to your home year after year? If so, don't wait until they're covering your windows in the spring. Fall is the time to get ahead of them. Send us a message or give us a call 705-878-1616.
We have been serving the Kawartha Lakes and surrounding areas for 25+ years. We're local, we're family owned and operated, and we know Ontario pests. We're here to help you stay one step ahead of them.
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