Living With Spiders: Which Ones Matter and Which Ones Don't
Of the roughly 3,500 spider species in North America, fewer than a dozen pose any meaningful medical risk to humans. The cellar spider in the garage corner, the wolf spider that startles you when you move a box, and the jumping spider on the windowsill are essentially harmless — and they're actively reducing your indoor pest population by eating flies, gnats, and small roaches.
If you can tolerate them, leaving most spiders alone is the right call. If you can't — or if a spider is in a location where someone is likely to be bitten by accident — here's how to reduce populations and identify the few species that warrant real attention.
Common Household Spiders You Don't Need to Worry About
- Cellar spiders ("daddy long-legs"): thin-bodied, very long legs, hangs upside down in messy webs in corners and basements. Cannot bite through human skin in any meaningful way. Helpful predator.
- House spiders: small, brown, build tangled webs in undisturbed corners. Some species are essentially synanthropic — they don't survive outdoors in many climates.
- Wolf spiders: large, hairy, fast-moving. They're free-ranging hunters that don't build webs and are often found near doors or basements where they wandered in. Not aggressive; bites are rare and medically minor.
- Jumping spiders: small, often colorful, with disproportionately large front eyes. Active during the day on walls and window frames. Visual hunters with curious behavior; harmless.
- Orb weavers: build large circular webs, often outside on porches and around lights. Rebuild the web nightly. Beneficial predators of moths and flies.
Spiders That Warrant Identification and Caution
Brown Recluse (Loxosceles reclusa)
Range covers the south-central U.S., roughly Texas through Tennessee and up to southern Iowa. About 6–20mm body with a dark, violin-shaped marking on the cephalothorax (the front body segment) — though this marking is not fully diagnostic and many other species have similar marks. The most reliable identifier is six eyes arranged in three pairs (most spiders have eight). Lives in undisturbed, dry locations — basements, attics, storage boxes, infrequently-worn shoes.
Bites are uncommon and usually occur when the spider is pressed against the skin (rolled onto in bedding, in a sleeve, in a shoe). Most bites resolve without medical intervention; a small percentage develop necrotic lesions that require professional treatment. If you suspect a recluse bite, capture the spider if possible and seek medical evaluation.
Black Widow (Latrodectus species)
Range covers most of the U.S. Adult females are shiny black with a red hourglass on the underside of the abdomen. Found in undisturbed locations: woodpiles, sheds, garage corners, outdoor electrical boxes, under deck stairs. The web is irregular and unusually strong; the spider hangs upside down at the center.
Black widow venom is a neurotoxin and bites cause significant systemic symptoms (cramping, sweating, hypertension). Fatalities are extremely rare with modern medical care, but bites warrant prompt medical attention, especially in children and the elderly.
Yellow Sac Spider (Cheiracanthium species)
Small (3–10mm), pale yellow to green, fast-moving, often found indoors in late summer and fall. Builds small silk retreats in upper corners of rooms. Bites are uncommon but produce a localized reaction comparable to a wasp sting in most cases. Usually does not require medical treatment unless symptoms persist.
Hobo Spider (Eratigena agrestis)
Found primarily in the Pacific Northwest. Builds funnel-shaped webs in dark, ground-level locations. Older literature attributed serious bite reactions to hobo spiders, but more recent research (and the 2017 removal of the hobo spider from the CDC's list of medically significant spiders) has substantially revised that view. Bites appear to cause only minor local reactions in most cases.
How to Reduce Indoor Spider Populations
Spiders are predators — they go where their prey is. Reducing the prey reduces the spiders, and is more effective than spraying for the spiders themselves.
1. Reduce Lighting Insects Attract
Outdoor lights at doors and windows attract flying insects, which attract spiders. Switch to yellow "bug" bulbs (lower attractiveness to most flying insects) or place lights on motion sensors. Aim lights down at the area you want lit rather than out into the yard.
2. Vacuum Webs Routinely
Weekly vacuuming of corner webs and undisturbed areas removes both webs and the spiders themselves. This is the single most effective non-chemical control. Use a wand or extension to reach high corners, ceiling fan blades, and behind furniture.
3. Reduce Outdoor Harborage Near the Building
- Move firewood, brick piles, and lumber stacks at least 10 feet from the foundation.
- Trim shrubs and ground covers back from foundation walls.
- Clear leaf litter from the perimeter.
- Seal storage boxes in plastic totes rather than cardboard, especially in basements and garages.
4. Seal Entry Points
Spiders enter via the same gaps that admit other pests. Caulking around windows and pipe penetrations, replacing worn weatherstripping, and installing tight-fitting door sweeps reduce both spider entry and the prey insects spiders follow.
5. Targeted Insecticide (Where Justified)
Most spider sprays sold to homeowners are pyrethroid-based residuals labeled for crack-and-crevice application. Spider populations rarely justify a perimeter spray on their own; if you're applying perimeter pesticide for ants, roaches, or other pests, the same application typically reduces spider activity as a secondary effect. We do not recommend spider-specific spray programs in most residential settings.
Glue Boards as Monitors
Sticky monitors placed along baseboards in basements, garages, and storage rooms can capture wandering spiders and serve as an indication of overall pest pressure. Place them in corners and along the wall, not in the open. Check monthly.
What About Spider "Repellents"?
Peppermint oil, chestnuts, vinegar sprays, and ultrasonic devices have all been promoted as spider repellents. None has good evidence behind it. Spend the effort on prey reduction, sealing, and routine vacuuming — that's where the actual results come from.
When to Call a Professional
- You suspect a brown recluse or black widow infestation in living spaces (not just exterior or outbuildings).
- You have a confirmed bite from a medically significant species.
- Spider activity is part of a larger pest problem (mass insect pressure attracting predators).