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K-State Research and Extension News

Now you see them: Brown recluse spiders become active in March

Kansas State University scientists have conducted a multi-year study.

brown recluseReleased: March 3, 2016

MANHATTAN, Kan. – They have a bad reputation for their venom, but brown recluse spiders truly are shy and would rather escape an encounter with a human than bite, according to Kansas State University research entomologists who have been studying the creatures for the past five years.

In fact, research associate Holly Schwarting and graduate student JR Ewing, both in Kansas State’s Department of Entomology, have hand collected more than 600 brown recluse spiders from homes and other buildings. They said none were aggressive or tried to bite, but the spiders did, however, try to escape.

“Their first, middle and last inclination is to escape,” said Kansas State University associate professor Jeff Whitworth. “They are quick and can run rapidly for short distances.”

March is when homeowners typically start seeing the brown recluse, which sometimes can be identified by the violin or “fiddle” shape on its back.

“Brown recluse spiders typically are dormant from October into March,” said Whitworth, who is an entomologist with K-State Research and Extension. “That is when their food source – generally insects and other spiders – is also less available, even in controlled indoor environments, such as our homes.”

The spiders can be found outdoors, as well as indoors, throughout most of Kansas, although have not been confirmed from natural habitats in the northwest corner of the state, he said.

“They are so commonly observed in dwellings,” Whitworth noted, “that most folks don’t even realize they occur in nature.”

On average, the spiders produce about 50 eggs annually, which hatch in the spring or summer and reach maturity the following year. They are reclusive from the beginning. Though they can be cannibalistic, they don’t seem to be overly aggressive to each other, he said.

“In fact they really do not seem to be aggressive, period,” he added.

Whitworth provided more information about the brown recluse spider.

  • They willingly hunt down and kill their food, mainly smaller insects and spiders, although will feed on recently deceased (up to 72 hours) insects or spiders.

  • Some pest control operators’ approach is to kill the spider’s food source with a toxic insecticide. When the spider feeds on the recently killed prey, the insecticide usually kills the spider. In this way, the nuisance pests plus brown recluse spiders are controlled.
  • Pesticides that have “brown recluse spider” on the label will kill the spiders. However, recent research shows that they must be sprayed directly on the spider, or the spider must come into contact with the insecticide while it’s still damp for acceptable control.

  • Pesticides are less effective in controlling these spiders when applied to carpeted areas rather than on tile or other non-carpeted surfaces.

  • Commercially available sticky traps help monitor spider activity, but they will not eliminate a brown recluse population.

  • If bitten, people react differently based on individual sensitivities. However, only one death has ever been directly attributed to the bite of a brown recluse and, even in that case, other health factors were involved.

  • When you find a spider in your bathtub or sink, it did not crawl up the drain. It came from the overflow drain, or it fell into the tub or sink and couldn’t get out.

“Brown recluse spiders are common,” Whitworth said. “You don’t have to like them, but you might as well get used to the idea that they are and will continue to be living with us for a long time.”

More information about spiders and insects in Kansas is available at K-State’s entomology extension website.


K‑State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well‑being of Kansans.  Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K‑State campus in Manhattan.

Story by:
Mary Lou Peter

For more information:
Jeff Whitworth – jwhitwor@ksu.edu or 785-532-5656