Moving in for the winter toxic brown recluse spiders pose danger

December 15, 2008

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Brown recluse spider. Credit: Richard Houseman, University of Missouri

As the cold weather creeps in, so do brown recluse spiders. True to their name, the brown recluse is a shy, reclusive spider looking for a warm home. Drawn to clutter, closets and complex storage environments, the spiders actually want to stay away from humans. But, if care is not taken, people could find themselves sharing their home with one of 'the big three,' according to a University of Missouri entomologist. The brown recluse is one of three spiders in the United States considered venomous – the other two are the black widow and the hobo spider.

Brown recluse spiders are not aggressive, and because they are so reclusive, most bites happen by accident, according to Richard Houseman, associate professor of entomology in the MU College of Agriculture, Food and Natural Resources. If brown recluse spiders are known to be in a home, Houseman recommends checking clothing, shoes and bedding each time the items are used.

"Often, bites occur when a person puts on a jacket or clothing that has a brown recluse spider inside," Houseman said. "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:

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

"The spiders inject what's called a hemotoxin," said Houseman, who also is a state urban
entomology specialist with MU Extension. "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 likes to make a 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 said. "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."

Source: University of Missouri-Columbia