Spiders in the House Every Fall: Why, and What to Do

Same call every year, same two weeks: "We suddenly have spiders all over the house. Is that normal?" It is. Spiders in the house in fall are as predictable as the leaves coming down, and the reasons are specific. But normal does not mean you have to live with it, and it does not mean anything is wrong with your house either.

Here is what is really going on in September and October, which species you are probably looking at, what actually brings the numbers down, and when it is worth picking up the phone.

Why are there more spiders in the house in fall?

The explanation everyone repeats is that they "come inside to get warm." That is mostly a myth. Outdoor spiders are built for a Quebec winter: they spend it under bark, in leaf litter or inside an egg sac, and most would not last long in the dry air of a heated house. The ones in your basement in October were there in July. You just did not see them.

Three things change in September.

Mating season. Males of several species reach adulthood in late summer and start roaming to find a female. They leave their corner, cross the living room floor, fall into the bathtub. A moving spider gets noticed; a spider sitting still in a corner does not. The big one that "just got in" is often a male that has lived in the house all along.

They are bigger. Spiders that hatched in spring have been eating all summer. By September they are adults at full size. Same number of spiders, much easier to spot.

The buffet gets bigger. In fall, insects look for shelter: earwigs, Asian lady beetles, cluster flies. More insects indoors means more food, and spiders always follow the food. If you are also finding earwigs in the house this fall, the two problems are connected.

Which spiders live in Quebec houses?

Four show up in almost every home on the South Shore.

• The common house spider. Small, brown, round abdomen. This is the one behind the messy cobwebs in ceiling corners and around windows. It lives indoors year-round, and each egg sac (a small beige ball in the web) holds dozens of eggs.
• The wolf spider. Large, hairy, striped, fast. No web: it hunts on the floor, mostly at night. It is the star of fall phone calls because it genuinely does come in from outside under garage doors, then crosses the basement in plain view. Intimidating, not aggressive.
• The cellar spider. Tiny body, long thin legs, a loose web on the basement ceiling. People call it a daddy longlegs, though that name properly belongs to harvestmen, which are not spiders. It vibrates in its web when you get close. Harmless, and it eats other spiders.
• The funnel weaver. A big, fast, brown spider with a funnel-shaped web in a basement, garage or shed corner. This is the one people call the giant house spider, and usually the one at the bottom of the tub: it fell in and cannot climb the smooth side back out.

Are Quebec spiders dangerous?

Not in southern Quebec. The brown recluse does not live here. The black widow is not established here, and the rare sightings make the news precisely because they are exceptional. The species above bite very rarely, only when pressed against skin, and the bite looks like a mosquito bite. Most of the "spider bites" people describe to us turn out to be something else: fleas, bed bugs, mosquitoes or a skin reaction. If a lesion is getting worse, the right call is Info-Santé 811, not an exterminator.

The real issue with spiders is comfort, and above all what they tell you: a lot of spiders means a lot of insects.

How do you get rid of spiders in the house?

You do not need to spray the whole house. A spider walks on the tips of its legs and does not groom itself the way an insect does, so it picks up very little residual product. What works is cutting off the food, closing the doors and removing the next generation.

1. Reduce the insects. This is the main lever. Screens with no holes, food put away, lids on the garbage. Ants, earwigs or flies: deal with that first and the spiders follow.
2. Change the outdoor lighting. A white light over the door draws insects every evening, and spiders build right next to it. A yellow or amber LED bulb draws far fewer.
3. Seal the openings. Sweeps under doors, caulking around basement windows, mesh over vents. That blocks wolf spiders and, as a bonus, the mice that arrive in October.
4. Vacuum webs and egg sacs. Ceiling corners, window frames, under the basement stairs. Empty the canister outside right away. Every egg sac you vacuum now is dozens fewer spiders in spring.
5. Dehumidify the basement. Aim for under 50 percent. The moisture-loving insects (earwigs, sowbugs, silverfish) disappear, and the spiders that eat them go with them.
6. Move the woodpile and the clutter. Firewood, building materials and bins against the foundation are a spider hotel one metre from the door. Trim the hedge and any branches touching the siding too. In the basement, swap cardboard boxes for sealed plastic bins.

Do this in September and you will see the difference by October. If instead the basement of your home in Brossard, Longueuil or Saint-Lambert is already at dozens of spiders, we can come take a look: the first inspection is free, we respond the same day, and the first service is 15 percent off. Call 514-553-2070 or use the contact page.

When is it worth calling an exterminator for spiders?

A few spiders in a house is normal in Quebec, and nobody needs a treatment for that. We will tell you so over the phone. There are situations where it does make sense.

• Webs are back within a day or two. You clean the porch or the window frame and it is rebuilt by the day after tomorrow. That means a solid population outside, fed by a steady supply of insects.
• Dozens of spiders in a finished basement. A family room or a child's bedroom where you meet one every day is more than a seasonal blip.
• Egg sacs everywhere. In every window corner, under every stair. What you are looking at is next spring.
• The spiders are following another problem. Earwigs, ants, lady beetles, flies. In that case, one perimeter treatment handles both: we treat the insects they feed on, and the spider population drops with them.

A professional spider treatment is done mostly outside: the foundation perimeter, eaves, window frames and the underside of the deck, with removal of webs and egg sacs. Our technicians are certified and hold the Quebec CD pesticide permit.

Frequently asked questions

Do spiders really come up through the bathtub drain?

No. The trap under the drain is full of water and a spider cannot get through it. The one in your tub fell from the ceiling or wall overnight and cannot climb the smooth side. A glass and a piece of cardboard will get it out.

Do peppermint oil or chestnuts keep spiders away?

Not much, and not for long. The evidence is thin, and any effect lasts hours. A vacuum and a yellow bulb will do more than essential oils.

Is a fall treatment too late?

No. Spring is the best time for prevention, but a treatment in September or October quickly reduces what is already there, removes the egg sacs before winter, and keeps you from starting April with a full population.

The short version

More spiders in the house in fall comes down to mating season, adults at full size and a bigger insect buffet. Not the cold. Cut the food, seal, vacuum the egg sacs and dry out the basement: in most houses, that is enough.

When it goes beyond that, Extermination BETA is based in Brossard and serves the whole South Shore (Longueuil, Saint-Hubert, Saint-Lambert, Greenfield Park, La Prairie, Chambly) and Greater Montreal. Call 514-553-2070 or reach us through the contact page. We will tell you honestly whether a treatment is worth it, and the inspection costs nothing.