Cluster Flies

Signs You Have Cluster Flies

What homeowners spot first

1. Sluggish flies at windows on warm winter days
2. Flies clustering in attic spaces
3. Dead flies accumulating in window sills
4. Flies with golden hairs on their bodies
5. Large numbers of slow-moving flies

Cluster fly larvae are parasites of earthworms. Adults aren't associated with garbage or filth like house flies are. In fall, adults seek shelter in buildings, clustering in attics, wall voids, and around windows. They emerge on warm days throughout winter and become active again in spring. They're attracted to light, which is why they end up at sunny south and west-facing windows.

Cluster fly control works best as an early-fall preventive treatment, before adults find their way into your soffits and attic. We hit exterior walls, eaves, window frames, and attic vents with an organic-based barrier spray, then point out the soffit gaps and utility penetrations that need to be sealed for next year. For active winter and spring problems, we add attic treatment and walk through exclusion work to keep the cycle from repeating. Just $49 to get started on a subscription plan.

Where are these flies coming from in winter?

Cluster flies entered your home in fall to overwinter. They hide in wall voids and attics, emerging on warm, sunny days. They're trying to get outside, not breeding indoors.

Are cluster flies dangerous?

No. Cluster flies don't bite, don't spread disease, and don't breed indoors. They're a pure nuisance pest. The downside is volume: when hundreds wake up on a warm winter afternoon, they're hard to ignore.

How do I stop cluster flies from coming back next fall?

You need to do two things together. Seal the entry points (soffits, attic vents, gaps around windows and utility lines), and treat the exterior in early fall before flies start landing on the siding. We pair an organic-based barrier spray with an exclusion walkthrough so you're not fighting the same swarm next year.