Of the thousands of species of spiders in the United States, only the black widow and the brown recluse spiders are sufficiently poisonous to kill a human. Usually, a bite delivers too little toxin to kill, but children and immune-suppressed individuals are at greater risk. Black widow spiders come in three varieties: The black widow with the typical red hourglass-shaped marking on its abdomen; the southern black widow; and the northern black widow. To repel black widow and recluse spiders, use exclusion, vacuuming, trapping, and remove potential hiding places. If necessary, control spiders with insecticides.
Identify the spider to determine if you are dealing with a poisonous spider. You will be able to use more specific methods if you know whether the spider is a black widow, a brown recluse or harmless. All black widow spiders are shiny black, but the northern black widow has red dots and sometimes white stripes instead of the typical red hourglass marking on its abdomen. The female black widow's body is up to a half-inch long; the male is much smaller. The recluse spider is light brown, has a 3/8-inch-long body and a dark violin-shaped marking on its back. It has six eyes, while most spiders have eight. Its legs are not banded like some other spiders' legs.
Remove hiding places. The brown recluse hides in dark places during the day. Reduce clutter in your house. Place stored items into closed plastic bags or tight-lipped containers to prevent spiders from taking up residency. Use tape to seal the edges of cardboard boxes.
Vacuum up spiders and their webs. Dispose of the vacuum bag, containing the spiders, in the outside trash. The black widow spider is more easily detected than the brown recluse spider, because of its irregular web. The best time to look for the black widow spider is at night; it will hang upside down in its net. The black widow also stores egg sacs, the size of peas, in the net.
Seal cracks and crevices in your home with caulk, weather stripping or expanding foam. Sealing crevices will deprive the brown recluse spider of hiding places and prevent the black widow from entering. Install tight-fitting window screens to prevent entry from the outside.
Use glue-boards or sticky traps to catch spiders. These traps are especially effective against the brown recluse. Place glue traps on the floor, near closets or storage areas. These traps will not only catch a brown recluse spider, but any other crawling insect.
Apply insecticide to cracks and crevices where you suspect spiders are hiding. Use recommended pesticides in infested crawl spaces and attics. Apply pesticides to the outside of the house, if you detect spiders outside.
Glue traps are available at garden centers and some grocery stores. Aerosol pesticides are ineffective unless you make direct contact with a spider. It may take months to get rid of brown recluse spiders.
When using insecticides, follow label directions closely.