SPRINGFIELD — Brown recluse spiders become more active in the summer, but there are simple steps Illinois residents can take to deal with them.
The spiders, which are usually between about a quarter of an inch and three quarters of an inches, but can grow to be larger, have a distinct violin-shaped mark on the body. Because they are more active during the summer months, it is not uncommon to spot them in homes, and people should be aware that they do bite.
“They ordinarily bite in self-defense when they are pressed against the skin,” said Tim Cashatt, curator emeritus for Illinois State Museum. “And that usually happens when you put on clothing that has been in a closet for a while and not been worn.”
Bites can require medical attention if the spider injects a significant amount of venom. The bite usually turns a little red, and then purple, Cashatt said.

“The skin actually dies down to the muscle layer if there is a lot of venom there,” he said. “And then it heals from the bottom up. So there is a lot of draining involved.”
In rare cases, people have also been known to get a systemic infection from the bite, which is more serious and can get into the body’s organs. But that generally doesn’t happen, Cashatt said.
Unlike most spiders, brown recluse spiders do not weave webs and like to hide in dark places.
Simple measures can be taken to reduce the number of these spiders in the home.
“A lot of control can be done by simple housekeeping,” Cashatt said. “Doing a lot of vacuuming, picking up stacks of newspapers and magazines that are on the floor. Just try to reduce the places they can hide, to begin with.”
Just as its name suggests, recluse spiders do not migrate on their own, so the likelihood that they will move to other parts of the country due to warmer summers is unlikely.
“They are recluse spiders and they are named that for a reason,” Cashatt said. “They like to hide in dark, damp places. The spiders often hide in boxes in warehouses, and then are moved around as boxes are shipped from place to place.”