Why are there so many spiders in my house this fall?

Why there are more spiders in fall

Fall is mating season for many outdoor spiders: male grass spiders go looking for females and sometimes wander into homes, Ohio State Extension says. Wolf spiders occasionally slip in around doors and windows while hunting, Iowa State says.

True house spiders usually spend their whole lives in, on or under one building, the Burke Museum in Seattle says.

Where you find one tells you which kind it is:

From MSU Extension, Ohio State, Iowa State, Minnesota, Kentucky, the University of Michigan, the Connecticut station and the Burke Museum.

The big one on the basement floor: wolf and grass spiders

A big brown spider running across the basement floor in fall is likely a wolf spider or a wandering grass spider. MSU Extension says wolf spiders come in at ground level, and most homeowners see only one or two.

Ohio State says a grass spider's abdomen usually tapers to a point; a wolf spider's tends to be rounder.

The fix is a jar: Iowa State says one caught in a large jar can go back outside.

If your phone says brown recluse, MSU's Duke Elsner says such scares almost always turn out to be a local look-alike; our brown recluse guide shows how to tell.

The webs in the basement corners: cellar and house spiders

The webs in the basement corners belong to spiders that live there all year. Cellar spiders, pale with very long legs, build loose webs in corners, Minnesota Extension says, and the University of Michigan says they are not dangerous to people. Tangled cobwebs are often the common house spider, which MSU says is beneficial to tolerate.

Use a vacuum:

• Tap the web first. A tap from the switched-off nozzle sends the spider out, Connecticut's station says.
• Get the egg sacs. Kentucky Entomology says each one can hold hundreds of young spiders.
• Dry it out. Spiders and their prey dislike dry places, the station adds, so run a dehumidifier and fix leaks.

Large, persistent spider numbers indoors mean a big insect population is feeding them, Wisconsin's extension says. In a damp basement, that food can be the tiny bugs of a damp floor, which house centipedes hunt too.

The small sac in a ceiling corner: yellow sac spiders

A yellow sac spider hides by day in a small silk sac, which indoors may sit in a corner where a wall meets the ceiling, MSU Extension says.

MSU counts it among three native spiders that are medically important in Michigan. It hunts at night, and bites happen when one gets trapped against skin in sheets, clothing or shoes.

The truth is more likely to be that we have more to worry about from frail anemic looking spiders, particularly, the yellow sac spiders.

Howard Russell, Michigan State University Extension (2008)

Most bites are not serious. MSU says most are relatively painless; in worse cases one burns for up to an hour and can blister, and any sore that forms usually does not scar.

If someone is bitten, keep them calm and call Poison Control at 1-800-222-1222, the National Pesticide Information Center (NPIC) says.

What works, and what does not

What works:

• Dim the porch light. It draws the flying insects spiders eat, Penn State Extension says. Minnesota suggests yellow bulbs.
• Leave the firewood outside. Penn State says firewood stored indoors warms up, and spiders wintering in it may wake and crawl out.
• Tighten up at ground level. Iowa State says to seal cracks, fix the door sweep, trim shrubs and move debris back from the foundation.

Do it yourself, or call someone?

For a few wanderers and webs, you probably do not need anyone. Connecticut's station says spider control does not require pesticides.

Spraying the outside is no cure. Iowa State says it has little if any benefit, and Penn State says most sprays do little to keep spiders out. Minnesota and Kentucky do back a targeted treatment where spiders hide and get in.

Call when webs and egg sacs keep coming back, when large numbers turn up indoors, or if you suspect a black widow or brown recluse. Wisconsin's extension calls both very rare in the upper Midwest but says they need immediate attention.

That is what our spider control is for: on every visit we treat the outside, knock down webs and egg sacs, and cut down the insects that feed them. We also show you the gaps and torn screens to fix; we do not seal, caulk or repair. Spiders are on the Honorable Shield covered list.

Common questions

About this page

Nick Russler, Owner, Honorable Pest Control

Written by Nick Russler, owner of Honorable Pest Control in Ann Arbor, Michigan. The facts here come from Michigan State University Extension and its Plant and Pest Diagnostics lab, the University of Michigan, the Universities of Minnesota, Wisconsin and Kentucky, Iowa State, Ohio State, Penn State, the Connecticut Agricultural Experiment Station, the Burke Museum and the National Pesticide Information Center, all read on October 7, 2026. We do not diagnose bites; see a doctor about any symptoms. If something here is out of date or wrong, tell us and we will fix it.