You see more spiders in the fall because many of them are grown males out looking for a mate. Most of these spiders already lived in your house or right next to it. They are not running from the cold. They just walk around more, so you notice them on floors, walls and in the tub.
Spiders come up a lot in our Google reviews, and many folks are scared of them. If you are seeing them a lot, our residential pest control service treats inside and outside the home and starts with a free inspection.
Why do spiders show up more in late summer and fall?
Spiders show up more in late summer and fall because it is mating season for many kinds. The Burke Museum spider experts say the spiders you see then are mostly "sexually mature males wandering in search of mates."
Here is what that means for your home:
- Males leave their hiding spots and walk around looking for females.
- They walk across open floors, so you see them more.
- They fall into sinks and tubs and can't climb out.
- The same spiders were there all summer. You just did not see them.
Do spiders come inside to get away from the cold?
No. Cold weather does not pull spiders inside. Spiders don't need to stay warm the way we do. When it gets cold, outdoor spiders slow down and rest. The Burke Museum says fewer than 5% of the spiders you see indoors have ever been outside.
That is good news and bad news. The good news: you are not being invaded. The bad news: if you see a lot of spiders, they have been living in your home, and they have food there. Spiders eat bugs. More bugs inside means more spiders.
Which spiders are dangerous in Missouri?
Only two spiders in Missouri are a real health risk: the brown recluse and the black widow. That comes from the University of Missouri Extension guide on spiders. Most other house spiders are harmless to people.
| Spider | What it looks like | Where you find it |
|---|---|---|
| Brown recluse | Tan to brown, about 1/2 inch long, a dark violin shape on its back, 6 eyes instead of 8 | Dry, cluttered spots that don't get moved: boxes, closets, basements |
| Black widow | Female is shiny black with a red hourglass under her belly | Woodpiles, trash, boards and rocks, mostly outside |
| Common house spider | Gray with white marks and banded legs | Webs in corners, windows and basements |
| Wolf spider | Big and hairy, can reach a 4 inch leg span | Runs on floors and in basements, no web |
Sources: MU Extension and MU Integrated Pest Management.
How common is the brown recluse in Missouri homes?
The brown recluse is very common here. MU Extension says one study found it in about 70% of the Missouri homes that were checked. It likes quiet, dry, messy spaces with bugs to eat.
A brown recluse with its legs spread out is about the size of a quarter. Look for the violin shape behind the eyes. The neck of the violin points toward the back of the spider.
How do brown recluse bites happen?
Most brown recluse bites happen when the spider gets pressed against your skin. MU Extension says this often happens when people put on clothes or shoes that sat unused, with a spider hiding inside. Bites also happen at night, when the spiders are out hunting.
To lower the risk:
- Shake out clothes, shoes and gloves that have been sitting in a closet or garage.
- Keep clothes and towels off the floor.
- Store things in sealed plastic tubs, not cardboard boxes.
- Pull beds a few inches away from the wall, and keep bedding off the floor.
If you think you were bitten, see a doctor right away. MU Extension says fast care can stop a bad reaction.
What keeps spiders out of the house in the fall?
The best way to have fewer spiders is to have fewer places to hide and fewer bugs to eat. These steps come from the MU Extension spider guide:
- Seal gaps. Close cracks around doors, windows and pipes. Fix torn screens.
- Clear clutter. Move boxes, papers and old clothes out of basements and closets. Clutter is the first thing to fix.
- Vacuum. Suck up webs, spiders and egg sacs. Then seal the bag and throw it out right away.
- Use sticky traps. Glue boards catch brown recluse and wolf spiders well. They don't work on spiders that sit in webs.
- Clean up outside. Keep firewood, rocks and boards away from the house. Mow the grass, and trim bushes so they don't touch the walls.
- Change porch lights. Yellow lights by the doors draw fewer bugs, so fewer spiders come to eat them.
When should you call a pro about spiders?
Call when you keep seeing spiders after you clean up, or when you think you have brown recluses. A few house spiders in the fall is normal. A spider a day, or spiders in beds and clothes, is not.
MU Extension notes that pros can use products homeowners can't buy, and that a perimeter treatment works best when you also keep clutter down. Those treatments also wear off over time. That is why many homes do best with a plan that treats every few months, not just once.
Matt Turner grew up in Wentzville and has more than 20 years in pest control. At Hometown Pest Solutions in St. Peters, we treat homes inside and out, and our quarterly plans come with a 365-day pest-free guarantee. If spiders come back between visits, we come back too. You can learn more about Missouri spiders in our spider pest library.
Fall spider FAQ
Are fall spiders a sign of a bigger bug problem? Sometimes. Spiders follow food. If you see a lot of spiders, there may be a lot of other bugs inside for them to eat.
Will the spiders go away when it gets cold? The wandering slows down after mating season ends. But the spiders that live in your house stay there all winter.
Are wolf spiders dangerous? Wolf spiders are big and scary, but they are not one of Missouri's two dangerous spiders. They are hunters that run on the floor and don't build webs.
Can I spray for spiders myself? You can, but MU Extension says spray cans don't work well unless you hit the spider itself. Spiders hide in cracks, so it is best to treat where they hide.
How do I know if it is a brown recluse? Look for a tan or brown spider about 1/2 inch long with a dark violin shape on its back. If you can, catch it in a jar and show it to a pro.
Get help with spiders this fall
If spiders are showing up in your home in St. Peters, O'Fallon, Wentzville or nearby, we can help. Learn about our residential pest control service, request a free pest inspection, or call or text 636-297-1335. We are open 7 days a week.