Brown Recluse Spiders

Brown Recluse Spider (Loxosceles reclusa)

Two-month-old brown recluse spider bite (click to enlarge) Image: Jeffrey Rowland

Brown recluse spiders are not aggressive, and because they are so reclusive, most bites happen by accident, says Houseman, an associate professor of entomology in the MU College of Agriculture, Food and Natural Resources. But their bites are frightful.

If brown recluse spiders are known to be in a home, Houseman recommends checking clothing, shoes and bedding each time they're used.

"Often, bites occur when a person puts on a jacket or clothing that has a brown recluse spider inside," Houseman says. "If the spider feels trapped against a person's skin, it will bite in self-defense."

If bitten, there are some important actions to take immediately:

1. Wash the site of the spider bite.
2. Apply a cold compress.
3. Apply a general antibiotic to the site to minimize the risk of secondary infection.
4. See a doctor as soon as possible and try to capture the spider and take it with you so the bite can be confirmed as that of a brown recluse.

"The spiders inject what's called a hemotoxin," says Houseman. "The hemotoxin produces a blister that turns black and sloughs off within 24 hours leaving an ulcerous open wound that takes six to eight weeks to heal, leaving a permanent scar. In very rare cases, the bite may lead to fever, rash, vomiting, coma, and death within two or three days."

The brown recluse seeks its winter home in attics, basements, or areas where things are placed and left for long periods of time. The spiders are drawn to boxes of papers or files, which have a lot of cracks and crevices to use for hiding. Minimizing clutter in and around the home and sealing boxes are important ways to reduce the chance of a large brown recluse population in a home. Bug sprays do not work for ridding a home of brown recluse spiders. Like many spiders, they have long hairs on the bottom of their feet that enable them to walk across treated surfaces without getting a lethal dose. However, professional pest control companies have products that can be effective when applied to the spider's hiding places, according to Houseman.

"The best idea is to use sticky traps because the spiders will move onto the sticky traps and be caught," Houseman advises. "The traps can be thrown away and replaced easily. Over time, there will be fewer spiders caught, which indicates the population has been greatly reduced."