Cluster Flies & Asian Lady Beetles: Why They Swarm Adirondack Homes Each Fall

Every fall in Glens Falls, Queensbury, and across the Adirondacks, I get calls from homeowners who suddenly see bugs piling up on siding or finding their way indoors. Two of the most common culprits are cluster flies and Asian lady beetles, but stink bugs and western conifer seed bugs also make appearances.

They’re called fall invaders or overwintering pests because they don’t breed inside your home—they just sneak in when the temperatures drop and settle in until spring.

What’s Really Happening Each Fall

• Cluster flies look a lot like houseflies but are slower and a little larger. Their larvae actually develop in earthworms outdoors, not in your food. In late summer and early fall, adults gather on warm, sunny walls before slipping inside through cracks and gaps.
• Asian lady beetles are often mistaken for the harmless ladybug. These beetles are a different species that swarm in huge numbers, especially on sunny afternoons. Once inside, they give off a strong odor and can stain walls if crushed.
• Brown marmorated stink bugs and western conifer seed bugs are also common. They aren’t dangerous but quickly become a nuisance when dozens of them show up in your living room on a warm winter day.

In every case, these pests are looking for a warm place to hunker down. Unfortunately, your attic, walls, and windowsills make perfect shelters.

Why It’s a Problem for Adirondack Homeowners

While fall invaders don’t reproduce indoors, they’re annoying, messy, and can be stressful for families. I’ve seen homes with thousands of cluster flies buzzing against attic windows, and I’ve vacuumed up buckets of lady beetles from walls in Glens Falls neighborhoods.

The real frustration comes in late winter and early spring when we get a warm sunny day. These pests “wake up” and wander into living spaces, usually by the dozens. That’s when homeowners call me saying, “It feels like my house is infested all over again.”

My Approach: Seal First, Treat Smart

The best solution isn’t blasting sprays inside your home. Once these pests are behind your siding or in your attic, sprays just drive them deeper or flush them into your rooms.

Here’s how I handle cluster flies and lady beetles in Upstate NY:

1. Exterior Inspection: I check siding seams, attic vents, soffits, ridge caps, and around windows and doors.
2. Exclusion Work: Sealing cracks and gaps is the single most important step. I focus on the south- and west-facing sides of the home, since those warm up fastest.
3. Targeted Treatments: If needed, I apply label-compliant materials at entry points before peak activity (usually late August through September).
4. Interior Strategy: I recommend vacuuming pests that make it inside instead of smashing them—this avoids odor and staining.

Homeowner Prevention Tips

If you want to get ahead of fall invaders, here’s my checklist:

• Seal cracks and gaps around siding, trim, vents, and pipes.
• Install fine mesh screens over attic vents and chimneys.
• Replace or repair weather stripping around doors and windows.
• Reduce exterior lighting at night that draws beetles and stink bugs.
• Vacuum, don’t crush pests indoors to prevent odors and stains.

When to Call Me

The best time to act is before the swarm begins—late August into September is prime prevention season in the Adirondacks. If you’ve dealt with cluster flies, lady beetles, stink bugs, or seed bugs year after year, give me a call at 518-807-4324.

I’ll inspect your home, identify entry points, and set up a fall pest prevention plan that works. With the right sealing and treatment, you won’t be vacuuming bugs all winter long.

✅ Next Step for You: Don’t wait for the swarm. Call or text 518-807-4324 today to schedule a free inspection and get your home sealed before fall invaders arrive.