Fall Invaders in Edmonton: What They Are and How to Keep Them Out

29 October 2026

By BugsNPests · Last reviewed 30 October 2026 · 5 minute read

Quick answer: fall invaders are insects and other critters that move into homes as nights turn cold. In Edmonton the usual ones are boxelder bugs, cluster flies, Asian lady beetles (ladybugs), spiders and mice. Most do not bite or damage your home, and the best fix is to find and seal the gaps they use.

Key takeaways

Boxelder bugs, cluster flies and lady beetles move in as adults to wait out winter. They do not feed or breed indoors.
They often appear on warm, sunny walls first, then find gaps and cracks.
Vacuum them. Crushing can stain surfaces and some give off a smell.
Sealing entry points is the real solution. Spraying alone rarely holds.
Mice also move in during fall. Treat them as a separate, more serious problem.

Hundreds of bugs on your walls or windows? Call 780-716-3943 or send a photo on WhatsApp for a free ID.

The Most Common Fall Invaders in Edmonton

Edmonton note: boxelder bugs are a regular fall sight on Edmonton and central Alberta homes, especially near boxelder or Manitoba maple trees. Cluster flies and lady beetles are also commonly reported in Alberta each fall.

Pest	What it looks like	What it does	What to do
Boxelder bugs	Black with red-orange markings, about the size of a grape seed	Gather on sunny walls and doors, slip in through gaps, and become active on mild winter days. They do not bite	Vacuum, seal gaps, remove nearby leaf litter
Cluster flies	Slightly larger than a house fly, grey, slow and sluggish	Hide in attics, wall voids and window frames, then buzz at windows on warm days	Vacuum, seal roofline and attic gaps
Asian lady beetles (ladybugs)	Orange to red, with dark spots and a white M or W marking behind the head	Gather in groups, release an unpleasant smell and stain when crushed	Vacuum, do not crush, seal gaps
Western conifer seed bugs	Brown, flat-backed bugs about the size of a grain of rice	Come inside to overwinter and are mostly a nuisance	Vacuum and seal gaps
Spiders and millipedes	Varied	Wander in looking for shelter and prey	See spider control
Mice	Small grey-brown rodents	Move in for warmth and food, damage wiring and contaminate food	Seal gaps and call us. See mice control

Why Fall Invaders Come Indoors

Cold nights send them looking for warm, protected spots to survive winter.
Sunny walls warm up first, so they gather there before finding cracks.
Gaps around windows, doors, soffits, vents, siding and utility lines are the easy way in.
Attics, wall voids and window frames give them the steady temperature they need.

The adults that move in are not feeding or breeding in your home. They wait until spring. That is why you may see them waking up on mild winter days.

Are They Harmful?

Most fall invaders do not bite, spread disease or damage the structure. The main problems are:

Large numbers on walls, windows and ceilings
Stains and spots from crushed bugs and droppings
An unpleasant smell from lady beetles when disturbed
Dead insects that can attract other pests such as carpet beetles. See beetle control.

Mice are the exception. They can contaminate food, damage wiring and carry germs, so they need proper treatment.

What to Do and What Not to Do

Do	Do not
Vacuum bugs and empty the vacuum outside	Crush them on walls, curtains or fabric
Seal gaps around windows, doors, soffits and vents	Leave gaps and rely on sprays alone
Repair screens and replace worn door sweeps	Use indoor foggers
Clear leaf litter and debris from the foundation	Pile firewood against the house
Call a professional if numbers are large or keep returning	Ignore mouse droppings or scratching

How to Keep Them Out This Fall and Next Year

Inspect the outside. Check windows, doors, soffits, vents, siding and utility entries, especially on the sunny south and west sides.
Seal the gaps. Use caulk, weatherstripping and mesh. Replace worn door sweeps.
Repair screens and chimney or vent covers.
Clear debris. Remove leaf litter, rocks and mulch next to the foundation, and trim branches touching the house.
Remove stored insects indoors. Vacuum attic edges, window frames and corners.
Time it right. Seal gaps after the bugs leave in spring and before they return in late summer and fall.

When to Call a Professional

Call us if you have large numbers every day, bugs keep returning after vacuuming, you hear scratching in the walls or see mouse droppings, or you want an exterior inspection and treatment before winter. We find the entry points and treat the outside of your home so fewer bugs get in.

Call 780-716-3943 now, WhatsApp us a photo, or request a free quote. We answer 24/7.

Fall Pest Services in Edmonton

Mice control: plans from $450 + GST. See mice control packages.

Spider control: see spider control in Edmonton.

FAQs

Do fall invaders bite or damage my home?

Most do not bite or damage the structure. Boxelder bugs and cluster flies are mostly a nuisance, though they can leave stains and spots. Dead insects can attract other pests like carpet beetles.

Will they breed in my house?

The cluster flies, boxelder bugs and Asian lady beetles that move indoors are adults sheltering for winter. They do not feed or reproduce indoors, but they may wake on warm days.

Why are boxelder bugs on my sunny walls?

They gather on warm, sunny sides of buildings in fall looking for gaps to shelter in, often near boxelder or Manitoba maple trees.

Should I crush them?

No. Vacuuming is better. Crushing can stain surfaces, and some, like Asian lady beetles, give off an unpleasant smell when stressed.

How do I stop them coming back next fall?

Find and seal the entry points, repair screens, door sweeps and vents, and do it after they leave in spring and before they return in late summer and fall.