Why Are Cluster Flies Invading My Home in March?

Posted on 2025-03-12

As winter fades and temperatures begin to rise, many homeowners in Barrie, Collingwood, and Wasaga Beach start noticing an influx of sluggish, buzzing flies inside their homes. If you're seeing these pests gathering near windows or light fixtures, you're likely dealing with cluster flies—one of the most common overwintering pests in Southern Ontario. But why are they showing up now, and what can you do about them?

What Are Cluster Flies and Why Are They in My Home?

Unlike houseflies, cluster flies don’t originate from garbage or food waste. Instead, they start their life cycle outdoors, laying eggs in soil where earthworms are present. The larvae parasitize earthworms, developing into adult flies by the time late summer arrives. As temperatures drop in the fall, these pests seek shelter in warm structures, often squeezing into cracks and crevices of homes in Wasaga Beach, Collingwood, and Barrie.

The problem isn’t apparent until about March, when rising temperatures trick cluster flies into thinking it’s time to head outside. Instead of exiting through the same entry points they used in the fall, they often emerge inside your home, gathering near sunny windows as they try to escape.

How to Prevent Cluster Fly Infestations in Early Spring

If cluster flies are already inside your home, prevention will be too late for this season—but you can take steps to stop them from returning next year.

1. Seal Entry Points Before Fall – Conduct a thorough home inspection in Barrie or Collingwood before next winter. Seal cracks around windows, doors, and soffits using caulking or fine mesh screens.
2. Inspect Attics and Wall Voids – Cluster flies often hibernate inside walls or attics. Professional pest control services in Wasaga Beach can apply treatments in these areas to prevent future infestations.
3. Use Vacuum Removal – Unlike fruit flies, cluster flies are not drawn to food, so baits and traps won’t work. Instead, use a vacuum to remove them quickly without crushing them (which can cause an unpleasant odor).
4. Consider Preventative Treatments – A professional exterminator in Collingwood can apply residual treatments in the late summer or early fall to deter flies before they settle in.

Professional Cluster Fly Control in Southern Ontario

If your home in Barrie, Collingwood, or Wasaga Beach experiences cluster fly invasions every spring, it may be time to consult a pest control specialist. Prevention is the key to avoiding the yearly cycle of cluster flies, and early intervention can ensure they don’t return next season.

By addressing entry points and seeking professional pest control services, you can enjoy a pest-free spring and avoid the hassle of cluster fly infestations in March.