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Cramer's brown recluse spider research published

Barry McNamara

The current harsh winter has added a new field of inquiry to Monmouth College biology professor Ken Cramer’s ongoing study of the brown recluse spider: Can the poisonous arachnid survive a polar vortex?
“Having a native, wild population that I can study has been a big help,” said Cramer, who a few years ago discovered the spiders in the garage and basement of a faculty colleague. “If they survive this winter, I’ll be impressed.”
Five years ago, research conducted by Cramer and one of his former students, Alex Maywright ’05, determined “a limiting temperature of –5 degrees Celsius for brown recluse overwinter survival.” That equates to 23 degrees Fahrenheit, but the weather in western Illinois has been much colder this year.
Because the spiders tuck themselves deeply into the cracks and crevices of their dwelling area, Cramer said it won’t be known until April if the local population has survived this year’s polar vortex.

Cramer’s brown recluse research is featured in the current issue of the Journal of Medical Entomology. Co-authored with Richard Vetter, a research associate in the department of entomology at the University of California-Riverside, the article is titled “Distribution of the Brown Recluse Spider in Illinois and Iowa.”
“This paper came out of a project I started in 2002 (the Illinois-Iowa Brown Recluse Spider Project), collecting specimens that the public sent me,” said Cramer, who added the project is ongoing. In fact, he plans to do a survey of the recluse spider in Monmouth this summer. Monmouth is on the northern edge of the spider’s distribution, according to the data he’s accumulated.
“In Illinois, brown recluse spiders are common in the southern portion of the state and dwindle to almost nonexistence in a transition to the northern counties,” he wrote in the article’s abstract.
Among other advantages, Cramer’s research will help medical personnel better determine if “loxoscelism” – a brown recluse spider bite – is the cause behind patients displaying necrotic skin lesions.
“Information about the distribution of the brown recluse in North America is essential for accurately diagnosing spider bites, yet knowledge about its distribution is sometimes fragmentary or incomplete,” wrote Cramer.
Cramer, who said a national monitoring network for the brown recluse spider is in the works, uses the basement population to supply his lab in the college’s Center for the Science and Business – and to get them out of his colleague’s house. The spiders in the non-attached garage provide his wild population.
The professor, who joined Monmouth’s faculty in 1993, is using his sabbatical this semester to work on another paper about brown recluse spiders, and he will build an olfactometer to see if they use the sense of smell to find their prey.
Another aspect of his research is tracking individual spiders. When he and his biology students conduct research on turtles in a freshwater pond north of campus, they are able to mark the underside of the turtles’ shells. Tracking the spiders requires a little more work, but Cramer has been able to devise a system that places a tiny number on their backs. It involves keeping the spiders down, temporarily, with some carbon dioxide and a small restraining device.
While Cramer hopes his outdoor population makes it through this chilly winter, another of his students, senior Lindsey Zagar of Plainfield, is researching their temperature tolerance on the other end of the spectrum.
“Lindsey is investigating their upper thermal limits – how hot they can take it,” he said. “Sometimes, when a population of bedbugs needs to be eradicated, heaters will be brought into the room and cranked up to 140 degrees. This could also prove to be effective for getting rid of recluses. Pesticides are often ineffective on recluses because of their ability to retreat so deeply into a structure.”
To contact Cramer about a possible brown recluse spider or to send him a specimen, visit his website: or contact him at