Nov. 7, 2003

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Contact: Dan Lara, University Relations, (785) 864-8855.

KU researcher: Pesticides may help rather than harm brown recluse spider

LAWRENCE -- Jamel Sandidge once entered a house in Lenexa and found more than 80 brown recluse spiders in less than an hour. In the three years he has studied the small but potentially deadly beast, he finds an average of 65 brown spiders inhabiting a typical home in the Kansas City area.

So many spiders in one place made Sandidge to wonder how these creatures build and maintain their large numbers. His research led him to a surprising discovery: While the brown recluse will sometimes eat live prey like other spiders, it also is a scavenger, preferring dead over live prey.

Sandidge, a doctoral student in ecology and evolutionary biology at the University of Kansas, had his findings published in the Nov. 6 edition of "Nature" magazine.

"There is very little biology known about the species," Sandidge said. "I wanted people to understand something about the species and why it's so hard to get rid of them."

The brown recluse is a common pest found throughout the central and southern United States. In northern areas of the brown spider's reach, including Kansas and Missouri, it typically lives indoors because of the colder climate, Sandidge said.

For his experiments, Sandidge observed spiders in 71 homes in Kansas and also conducted prey-choice experiments in a lab. In more than 25 homes, he found brown spiders actually avoiding live prey, instead locating and consuming dead prey.

For the lab experiments, he placed adult male and female brown spiders into separate plastic boxes and fed them a variety of insect prey, both dead and alive, once a week, and then starved them for two weeks. The spiders were then presented with equally sized live and dead prey. Almost 85 percent chose the dead prey over the live prey, indicating a clear preference.

Sandidge says his findings have implications for how people control brown recluse infestations in their homes.

"Current practices involve spraying and fogging or fumigation," Sandidge said. "This kills all living organisms, good or bad, except the brown recluse. Overall these methods are not very effective, except in the short term."

In contrast, spraying pesticides may actually increase the number of brown spiders by providing killed insects as a food source, as well as leaving less competition from other spiders, Sandidge said.

"Basically, pesticide applicators have always said the only real way to get rid of them is to kill off their food supply, hoping they will either starve or leave the premises," Sandidge explained. "My study shows this idea of killing all potential prey has only helped these spiders, making their meals easier to find."

Bites from brown spiders can cause slow-healing wounds and severe tissue damage. Sandidge estimates that thousands of people are bitten each year.

"The fear of brown spiders is warranted," he said. "They're pretty nasty."

Sandidge has taken his spider expertise and expanded it beyond his doctoral studies. Brown Recluse Solutions was started by Sandidge in 2002 to educate the public about brown spiders, as well as detect and control them. He conducts home consultations and advises the pesticide industry. Sandidge will design and implement a specific plan to reduce spider infestations for every home he visits.

In addition, Sandidge runs a Web site connected to his research known as the Recluse Community Project, which provides detailed information about the infamous spider.

Sandidge's reputation and expertise have garnered the respect of other researchers in his field.

"Among spider biologists, his work is very well received," said Deborah Smith, associate professor of ecology and evolutionary biology at KU. "He is very effective in obtaining outside financial support for his research and in interacting with the public."

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