researcher: Pesticides may help rather than harm brown
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"
"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
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
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
In addition, Sandidge runs a Web site connected to
his research known as the Recluse Community Project,
which provides detailed information about the infamous
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."