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Cluster fly control in Toronto, the GTA and cottage country
Cluster flies look like large, slow house flies. In the fall they gather on sunny walls and squeeze into attics and wall spaces to spend the winter, then show up at windows on warm days.
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How to identify cluster flies
How to tell cluster flies from house flies.
Cluster flies
Larger and slower than house flies, with golden hairs on the back. They often gather in groups at windows.
House flies
Smaller, quicker and grey with dark stripes. They breed in garbage and waste, not in walls.
Signs to look for
- Groups of slow, sluggish flies at sunny windows in fall or late winter
- Flies on south and west facing walls in September and October
- Dead flies collecting on window sills and in attics
- Flies appearing in upper rooms on warm winter days
Why cluster flies come inside
What draws them in
Cluster flies spend the summer outside, where their young feed on earthworms. As the weather cools, adults look for a sheltered place to spend the winter, and the attics and walls of homes are ideal.
Health and home risks
Cluster flies don't bite and aren't known to spread disease, but large numbers in living spaces are unpleasant, and dead flies can attract other pests.
How we handle cluster flies
Treat before they move in
Exterior treatment on sunny walls in late summer, before flies settle in for winter.
Find where they're getting in
We look at gaps around windows, siding, soffits and vents.
Treat attics and wall spaces
Where flies are already inside, we treat the spaces they shelter in.
Clean up
Advice on removing dead flies so they don't attract other pests.
Prevention tips
- Seal gaps around window frames, siding and soffits
- Repair torn window screens
- Fit screens over attic and soffit vents
- Book exterior treatment in late August or early September
- Vacuum up flies at windows rather than crushing them
Common questions about cluster flies
Why do I see flies in the middle of winter?
Cluster flies that sheltered in your walls or attic wake up on warm, sunny days and move toward the light, ending up at windows inside.
Are cluster flies breeding in my house?
No. They breed outdoors in soil. The ones you see inside came in to spend the winter.
Related pests
Reviewed by PestDepart's licensed exterminators. For health concerns, including bites or stings, contact your doctor or local public health unit.