Quick answer: The sudden jump in spiders in the house each fall is mating season, not a cold-weather invasion. From late August through October, mature male giant house spiders and hobo spiders leave their webs and roam through Salem homes looking for females. Neither is considered a serious bite risk. Sticky traps along baseboards, sealed gaps, less clutter and fewer insects around your doors thin them out quickly.
Key takeaways
- The September and October spider spike in Willamette Valley homes is driven by mature male giant house spiders and hobo spiders searching for mates.
- Spiders are cold-blooded and are not drawn indoors by your furnace; most of the ones you see inside have lived there all along.
- Hobo spiders are shy, and in a 2014 review of 33 verified Oregon spider bites cited by the Oregon Department of Agriculture, none caused significant medical symptoms.
- Sticky traps along baseboards, door sweeps, sealed gaps and fewer stored boxes reduce indoor spiders more reliably than spraying.
Why are there so many spiders in my house in September?
Because the big brown spiders of the Willamette Valley reach adulthood in late summer, and the males go looking for mates. That search takes them across floors and into bathtubs, which is where you meet them.
The spider most Salem homeowners are describing when they call us is the giant house spider (Eratigena atrica). According to Washington State University’s Pestsense guide, it is common in and around homes west of the Cascades and is most often seen from mid-summer to early fall, when the males in particular are highly mobile.
The females stay put in a flat sheet web with a funnel at one end, tucked in a basement corner, a garage or a crawl space. The males abandon their webs and wander for weeks. A male crossing your living room at 10 p.m. is not hunting you. He is following the scent of a female who may live under your house.
Hobo spiders (Eratigena agrestis), a close relative, follow the same calendar. Oregon State University’s Solve Pest Problems guide notes that male hobo spiders turn up in homes and garages in late summer and early fall. Both species are poor climbers, which is why they end up stranded in sinks and tubs: they fall in and cannot climb back out. They did not come up the drain.
Spiders in the house this fall: which ones are you actually seeing?
Around Salem and Keizer, five spiders account for nearly every fall call we get.
| Spider | Size and look | Web | Where you find it | Concern level |
|---|---|---|---|---|
| Giant house spider | Body 1/2 to 1 inch, leg span up to 4 inches; brown to gray-brown, long hairy legs | Flat sheet web with a funnel | Basements, garages, crawl spaces, bathtubs; males on floors and walls at night | Low. Bite not known to pose a threat to people |
| Hobo spider | Body up to 3/4 inch; brown, chevron pattern on the abdomen, no leg stripes | Funnel web near the ground | Window wells, woodpiles, garage edges, lower floors | Low. Shy; not considered medically significant |
| Cross orbweaver | Body 1/4 to 3/4 inch; tan to orange with a white cross on the abdomen | Large round orb web | Porches, eaves, between shrubs and railings | Very low. Stays outdoors |
| Cellar spider | Small body, very long thin legs; pale tan or gray | Loose, messy web in corners | Ceilings, garages, crawl spaces | Very low |
| Yellow sac spider | Body 1/4 to 1/2 inch; pale yellow to greenish, no markings | No web; a silk sac where wall meets ceiling | Upper walls, ceilings, behind picture frames | Moderate. Painful bite, like a bee sting; see a doctor if it worsens |
Two you may be worried about: the western black widow lives in Oregon but is uncommon in the northern Willamette Valley, and the brown recluse does not occur here at all. The hobo spider’s reputation has not held up either. The Oregon Department of Agriculture points to a 2014 review of 33 verified spider bites in Oregon, one from a hobo spider, in which none caused significant medical symptoms. We cover all three in our guide to dangerous spiders in Oregon.
Do spiders come inside to get warm?
No. Spiders are cold-blooded and do not seek out heat the way a mouse does. The fall spike starts in late August, while Salem is still having warm, dry afternoons, weeks before anyone turns on a furnace.
The house spiders you see in fall are mostly year-round residents. Giant house spiders, cellar spiders and yellow sac spiders live their whole lives in the house and the sheltered spaces attached to it: the crawl space, the garage, the wall voids. Fall does not add many new spiders. It puts the ones you already had on the move.
What does pull spiders toward the house is food. Every porch light draws moths, midges and crane flies from dusk onward, and spiders set up where the eating is easy: door frames, window corners, the soffit above the garage. Wet October weather also pushes sowbugs and earwigs under doors, and hunting spiders follow them in.
What actually works: a fall spider plan for Salem homes
The most effective spider control is mechanical: traps, vacuuming, sealing and de-cluttering. Insecticide sprays kill only the spiders they hit directly, and OSU Extension does not recommend chemical control as the answer to spiders. Do these six things in order.
- Set sticky traps along baseboards. Wandering males travel along walls. Put flat glue boards behind furniture, under sinks, beside the garage door and in basement corners. They show you where spiders come from and catch wanderers before they reach the bedroom.
- Vacuum webs, egg sacs and spiders. A vacuum wand handles ceiling corners, window tracks and the funnel webs in the garage. Empty the canister outside.
- Clear the floor. Cardboard boxes and piles of anything against a wall are spider habitat. Move storage into sealed plastic totes on shelves, especially in the garage.
- Seal the entry points. Install door sweeps and weather stripping, repair window screens, and caulk the gaps where siding meets the foundation and where pipes enter. The same fixes keep out boxelder bugs and mice; our fall pest-proofing checklist walks through them in order.
- Manage the lights. Move porch lights away from doors where you can, or put them on motion sensors. Fewer insects at the entrances means fewer spiders waiting there.
- Cut back vegetation. Trim shrubs and ivy touching the siding, and keep firewood off the ground and away from the house.
Why the Willamette Valley is spider country
Our mild, wet climate suits the European house spiders that dominate valley homes, and the way we build here gives them plenty of room.
Salem winters rarely stay below freezing for long, so spiders in a vented crawl space or an unheated garage stay active most of the year. The October rains keep the crawl space humid, and the insects spiders eat keep breeding under the house all winter.
Housing matters too. A large share of Salem and Keizer homes went up between the 1950s and 1980s with vented crawl spaces, lap siding and original windows. Every torn vent screen and every gap under a door is a highway for a wandering male. Homes on the farmland edges around Dallas tend to see more hunting spiders, wolf spiders especially, because there is more ground cover and insect life next door.
When to call a professional
Call when you are catching several spiders a week on traps, when webs come back within days of cleaning, or when you find a black widow or a spider you cannot identify.
Our spider inspection starts outside, where we look for the entry points: crawl space vents, weep holes, gaps around hose bibs, the soffit line, and the outdoor lights that feed them. Inside, we check the basement, garage, utility room and window tracks, and we de-web the eaves, porch and entries. A perimeter treatment with EPA-registered products, applied according to the label, targets the cracks and voids spiders and their prey use to get in, and it works best paired with the sealing steps above. We tell you exactly what to expect, including any re-entry times, and we offer family- and pet-considerate options.
Read more about our spider control service, or ask us anything by phone. AAA Pest Exterminators has been family-owned and operated in Salem since 1997, and we do not ask you to sign a long-term contract. If the inspection turns up ants, rodents or wasps feeding the spiders, our full list of pest control services covers those too.
Frequently asked questions
Are giant house spiders dangerous?
No. Washington State University reports that the bite of the giant house spider is not known to pose any threat to people, and the spider is not aggressive. It looks alarming because of its size, up to four inches across the legs, but it would much rather run than bite. Trap it under a cup, slide a card underneath and carry it outside.
Do spiders come inside when it rains?
Not in large numbers. The fall spike begins in late August, before the rainy season starts in October, and it is driven by mating, not weather. Rain does push some outdoor insects under doors, and hunting spiders sometimes follow them in. A tight door sweep and good weather stripping solve both problems at once.
Should I spray for spiders inside my house?
We do not recommend it as a first step. Insecticide sprays labeled for spiders kill only the spiders they hit directly and leave little lasting protection, so spraying the baseboards mostly treats your floor. Sticky traps, a vacuum and sealing do more. When a treatment is warranted, we target the outside entry points and the insects spiders feed on.
How long does spider season last in Oregon?
The wandering-male season for giant house spiders and hobo spiders runs from late August into October in the Willamette Valley, and sightings usually taper off in November as the males die. Females and egg sacs remain in the house year-round, so finding a few spiders in the garage or crawl space in January is normal, not a sign of a new problem.
Pests in the nest? Don’t stress. Call the best.
Family-owned and operated in Salem since 1997. No long-term contracts. Serving Salem, Keizer, Albany, Dallas, Woodburn and McMinnville.
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