Spiders in and around the house

Many kinds of spiders live in and around houses. Most are harmless, and they help by eating flies and other insects. Most have fangs too small or weak to break human skin, and the ones that can bite usually don't unless they're trapped against the skin or their nest is disturbed. Two can give a serious bite: the black widow and the brown recluse.

The two to know

Black widow

The adult female is about 1/2 inch long and shiny black, usually with a red hourglass on the underside of the abdomen. In some, the hourglass is broken into separate red spots. Black widows spin loose, messy webs. Outdoors they live under rocks, boards and yard debris such as stacked flower pots. They're seldom found indoors, and when they are, it's usually in garages, entryways, sheds and outbuildings. Most bites happen when someone lifts an object or reaches into a spot where one is hiding.

The venom affects the nerves and works quickly. It can cause painful stiffness of the belly, tightness in the chest, sweating and nausea. Clean the bite, put ice on it, and get medical care promptly. Most bites respond to treatment, and an antivenin exists for severe cases.

Brown recluse

The brown recluse is cream-colored to dark brown, with a darker abdomen and a violin-shaped mark on the front part of the body. It has six eyes, where most spiders have eight. It's easy to confuse with harmless brown spiders. It hunts at night and hides by day in shoes, clothing, boxes, closets, basements, attics and crawl spaces. People are bitten putting on a shoe or a piece of clothing it's hiding in, or when one crawls into a bed. It's rare where winters are cold and the climate is dry.

The bite is usually painless at first. Three to eight hours later it can turn red, swollen and tender, and it may become an open sore that takes a month or more to heal. Prompt medical care can limit the damage. If you can, catch the spider and bring it in to be identified, so the doctor knows what bit you.

Keeping spiders down

• Vacuum or sweep the webs, the spiders and the egg sacs. Each egg sac can hold hundreds of young.
• Cut the clutter in closets, garages and basements, where spiders like quiet, undisturbed spots.
• Clear the outside walls. Move firewood, stacked items and debris away from the foundation. Trim shrubs and vines that touch the house.
• Close the gaps. Tight window screens and door sweeps keep spiders out, and so does caulk along cracks near baseboards and doors.
• Change the porch light. Yellow or sodium vapor bulbs at outside doors draw fewer night-flying insects, which in turn draw fewer spiders.
• Put down glue traps flush along walls and in corners. They catch wandering spiders and show where they're most active.

Wear heavy gloves when you reach into boxes or move stored things in a garage or shed. An infestation of black widows or brown recluses usually takes a pest control company to clear.

An annotated example

What to do next

Vacuum the corners, the webs and the egg sacs in the basement, the garage and the closets. Set a few glue traps along the walls to see what you have. Learn what a black widow and a brown recluse look like, and wear gloves when you dig through stored boxes.