Spider Control: How to Handle House Spiders and Spot the Few That Matter

Cobwebs keep coming back in the corners, or something big and hairy just ran across the basement floor. Most spiders that turn up in a house are harmless, and many are eating insects you would rather not have. This guide helps you tell common house spiders from the few that matter medically, and shows you how to cut their numbers without spraying the whole house.

How to identify common house spiders

Most spiders you find indoors wandered in from outside through doors, windows and other gaps. Homes near woods or with heavy plantings along the foundation tend to see more of them.

If you can, catch one on a sticky trap or in a jar before you decide what to do.

Spiders that matter medically

Only a few spiders in the US have venom that is seriously harmful to people. The black widow and the brown recluse are the two you need to know.

Black widows live throughout North America and are most common in the southern and western states. The adult female is shiny black with slender legs and a red or orange hourglass on the underside of her large, round abdomen. She hangs upside down in a tough, irregular, sticky web, which puts the hourglass on display. Males and young widows look quite different and are often tan with pale stripes. Males are much smaller, and their fangs are too small to break human skin.

Widows prefer dark, dry, sheltered spots: woodpiles, garages, eaves, fences, debris piles and clutter. People usually get bitten when they reach into one of those places while cleaning out or picking up items. Very little may show at the bite site, but the venom affects the nerves, and pain can spread to the chest, belly or whole body. Young children, older adults and people with health problems are more likely to have a severe reaction.

Brown recluses have six eyes arranged in pairs, while most spiders have eight. They are far less widespread than many people believe, and plenty of harmless brown spiders get mistaken for them. Our brown recluse guide explains how to confirm one, where they live and what to do about bites.

If a spider bites you, stay calm, wash the bite with soap and water, apply a cold, damp cloth or ice, and keep the area raised if you can. If you can do it safely, catch the spider so it can be identified. Get medical care promptly after any black widow or brown recluse bite, and right away for spreading pain, muscle cramps, sweating, fever, trouble breathing, nausea, or a wound that blisters or turns purple.

Signs of a spider problem

• Cobwebs that come back in corners, window frames, light fixtures or basement ceilings soon after you clear them.
• Egg sacs: small round balls of silk in or near a web. A black widow’s sac is about 1/2 inch across, creamy yellow to light tan, with a tough, papery surface.
• Lots of insects around porch lights and windows. Spiders follow their food.

Why spiders come inside

Spiders go where the insects are. Outdoor lights draw insects to your walls and doors at night, and spiders set up nearby. The more insects you have indoors, the more likely spiders are to settle in.

Other reasons you see them:

• Gaps around doors and windows, cracks in the foundation and torn screens.
• Hitchhiking on potted plants, firewood and boxes brought inside.
• Clutter, leaf litter and dense plantings against the foundation, which give them shelter right next to the house.
• Wandering males. Male wolf spiders roam in search of females and often end up indoors. New housing developments can see a wave of wolf spiders that lost their outdoor habitat.

How to get rid of spiders, step by step

Work through these in order. Most households never need to go past step 6.

1. Figure out what you have. Use the table above. If it could be a black widow or a brown recluse, wear gloves when you clean and read the safety notes before you go further.
2. Vacuum webs and spiders. Go over corners, under furniture, storage areas, basements and rooms you rarely use, and keep it up regularly. Spiders have soft bodies and usually do not survive the trip through the hose.
3. Cut down on the insects they eat. Move outdoor light fixtures off the house where you can, or at least away from doors and windows. If you have an indoor insect problem such as cockroaches, solving it takes away the spiders’ food.
4. Seal and screen. Close cracks in the foundation and gaps around windows and doors, and repair torn screens. Tight screens keep out spiders and the insects they hunt.
5. Clear hiding spots. Indoors, reduce stacks of boxes and clutter in basements, garages and closets. Outdoors, rake out leaf litter and trim plants back from the foundation. Wear gloves when you move stored items, woodpiles or debris.
6. Set sticky traps. Place them along baseboards, behind furniture and near doors where children and pets cannot reach them. They catch wandering spiders without insecticide and show you which spiders are still around.
7. Deal with strays directly. Crushing or vacuuming a spider you can see is quicker and less toxic than spraying it.

This order (inspect, clean, exclude, then use chemicals only if needed) is the heart of integrated pest management.

An honest look at spraying

Pesticides are not usually needed for spiders, and they are no long-term fix. Spraying kills only for a short time unless you also vacuum, seal and reduce clutter, because new spiders keep wandering in from outside. UC IPM specialists generally advise against using insecticides on spiders outdoors.

Products sold to homeowners for spiders usually contain pyrethrins or pyrethroids. If you choose to use one, treat only the cracks and corners where spiders hide, and read and follow the label. Insecticidal dusts made from silica are meant for professional applicators, who apply them to cracks, attics and wall voids. Before you buy anything, read our guide to using pesticides safely at home.

Wolf spiders

Wolf spiders startle people because of their size and speed. They are mostly dark brown, hunt on the ground and use no web to catch prey. Shine a flashlight across the lawn at night and their eyes glow green. Up close, they have a row of four small eyes in front, two large eyes above them, and two more toward the back of the head.

Outdoors they live in grass and leaf litter. Indoors they are accidental visitors and do not set up long-term populations. Most of the ones you find are adult males searching for mates. They have strong fangs and can bite if you pinch or handle one, so pick it up with a cup and paper or a gloved hand.

To keep them out, seal gaps under and around doors, clear leaf litter and dense plantings along the foundation, and set sticky traps just inside doors to garages and basements. A wolf spider has eight eyes, which is the quickest way to rule out a brown recluse.

When to call a professional

Cobweb spiders, cellar spiders and the occasional wolf spider are a DIY job. Vacuuming, sealing and traps will handle them.

Consider professional help if:

• You keep finding spiders you think are brown recluses, especially in bedrooms or closets.
• Black widows are nesting where children play, or you find several in a garage, crawl space or shed.
• Webs and egg sacs are in places you cannot reach safely, such as high eaves, attics or crawl spaces.
• You have vacuumed, sealed and trapped for several weeks and still catch a lot of spiders, which can point to a larger insect problem.

A good visit usually starts with an inspection inside and out. The technician should identify the spider and the insects it is feeding on, point out entry gaps and lighting or clutter problems, and then treat only where needed, such as cracks, voids and eaves. Ask them:

• Which spider did you identify, and is it one that can harm people?
• What is the plan besides spraying, such as web removal, sealing and changes to lighting?
• Which products will you use, where, and what should I do to keep children and pets safe?
• Is a follow-up visit or trap check included?

Our guide to choosing a pest control company has more questions to ask, and pest control costs explains what affects the price of a visit or service plan.

Spider questions

Should I just leave spiders alone? Outdoors, usually yes. Spiders are mostly beneficial because they eat pest insects. Indoors, vacuuming a few webs is all most homes need.

Do house spiders bite people in their sleep? Rarely. Most spiders have jaws too small to bite people, and those that can usually bite only when they are pressed or trapped. If you have a sore you think is a bite but never saw a spider, see a doctor, because many skin problems get blamed on spiders.

Will spraying around the foundation keep spiders out? Not for long. The effect wears off, spiders keep coming in through gaps, and UC IPM advises against outdoor spraying for spiders. Sealing gaps and moving lights does more.