Brown recluse spiders (Loxosceles reclusa) are unwelcome house guests in any home, but the best way to remove them varies according to the severity of the infestation. The normal range of the brown recluse spider is in the mid-western and south central areas of the United States, but isolated occurrences in other areas are sometimes reported. Wear a long-sleeved shirt, gloves, long pants, and shoes or boots when controlling brown recluse spiders, and either destroy them and de-clutter their hiding places, or spray heavy infestations with insecticides.
Identifying Brown Recluses
Other spiders are often mistaken for brown recluses. The best-known characteristic of brown recluse spiders is a violin-shaped mark on the part of the body where the legs are attached. The widest part of the violin is next to the eyes, and the neck of the violin points toward the abdomen. In young brown recluse spiders the violin can be hard to see, however, and other spiders have markings that look similar. A more accurate identifying feature is the spider's three pairs of eyes. Most other spiders have eight eyes in two lines of four. If the spiders infesting your home create large, wide webs across ceilings or other open spaces, they aren't brown recluses, which weave small webs behind objects.
Destroying the Spiders
If a few brown recluse spiders have wandered in from outside, destroy them. Put on protective clothing and hit the spiders with a rolled-up newspaper or a shoe. Alternatively, if you want keep a spider to have it identified by an expert, place a jar over the top of it and slip a piece of card underneath. Put a lid on the jar and put it in the freezer overnight, which sends the spider to sleep. Pour rubbing alcohol into the jar until the spider is covered, and leave it for an hour. If you're shipping the spider for identification, remove it from the alcohol before putting it in a small box and mailing it.
Trapping and De-Cluttering
Sticky cards called "glue boards" trap brown recluse spiders, and help identify where they're living. Brown recluse spiders live indoors in dark, quiet places such as garages, attics, crawl spaces, basements, heating ducts and suspended ceilings. They also live behind walls and baseboards, in closets, among stored items, and in crevices near beds. Outdoors they inhabit woodpiles, barns, and sheds and similar areas. Place glue boards in areas where spiders may be living, but keep the traps out of the reach of children and pets. Check the traps every day. Although the traps can destroy large numbers of spiders, by themselves they're unlikely to completely control a heavy infestation. You can carefully de-clutter areas where brown recluses are living -- wearing protective clothing and using a flashlight -- to flush spiders out for destroying, or spray the areas with insecticides.
A range of insecitcidal dusts and sprays control brown recluse spiders. Put on protective clothing including a safety mask and goggles before using insecticides, and follow the instructions on the label, or contact a professional contractor to deal with the brown recluse infestation. Silica gel and deltamethrin are two chemicals in insecticidal dusts that control brown recluse spiders. Chemicals for sprays that control brown recluse spiders include bifenthrin, cypermethrin, cyfluthrin, deltamethrin and lambda cyhalothrin. Puff dusts or spray insecticides into crevices and cracks where the spiders are living, and in outdoor entry points such as cracks in exterior walls, and along the base of foundations. Bug bombs and other fogging insecticide devices aren't usually effective against brown recluse spiders, though they may be the only option in inaccessible areas of the home.
If you are bitten...
Brown recluse spiders are very dangerous. If you are bitten, clean the bite wound, apply antibiotic ointment, ice the bite, and hold the bitten area up high if possible. Then, go immediately to get medical care, taking the spider with you (in a jar, as described above) if possible. It can also be helpful to call poison control (800-222-1222). Brown recluse spider bites are often painless initially, but can cause serious tissue damage if left untreated.