Watch out for that bite; brown recluse spiders set up homestead in Illinois homes

Most spiders are completely harmless to humans, according to the Illinois Department of Public Health. However, the brown recluse spider can present a problem — although the fear of the spider overstates its actual danger.

The brown recluse is an invasive species to Illinois, having been transported from the southwest United States through vehicles that contain the dark spaces the spiders prefer to hide in. There have been some infestations on campus, most recently in the Forbes Natural History Building.

The spider is about the size of a quarter and almost completely brown. Its only prominent marking is a violin-shaped mark near its eyes, with the neck of the violin facing away from the spider’s head.

Chris Dietrich, curator of insects at the Illinois National History Survey, located at Forbes, said the spiders are not a huge problem in Champaign-Urbana, but their bites should be treated.

“They tend to hang around in secluded areas: shipping crates, boxes, those kinds of things,” he said. “They’re pretty much all over the U.S. now, and I wouldn’t say they’re really super abundant, but they are common.”

Dietrich said the spider bite causes a necrotic reaction. The venom will kill the tissue around the bite and, especially if untreated, can cause secondary infections.

Fatalities, however, are very rare. According to entomologist Philip Nixon, there has only been one reliably recorded brown recluse death.

If the spider bite is initially misdiagnosed, the necrotic tissue around the bite may have to be removed, and a dermatologist may have to reconstruct the skin in severe cases, Dietrich said.

According to the Illinois Department of Public Health, brown recluse spider bites are rare — they are, after all, reclusive — and other injuries are often misdiagnosed as spider bites. According to the department, severe necrosis probably happens in less than 10 percent of bites.

The bites are “not particularly painful, no worse than a bee sting,” Dietrich said. “I’ve never been bitten by one, so I don’t know firsthand, but it’s not something to take lightly if you are bitten, and most people don’t actually see the spider when they are bitten because they might be pulling something out of a closet or emptying out a shipping container and accidentally brush up against a spider (that) will bite them, and then they’ll notice later.”

Rather than using pesticides to deal with the Forbes infestation, Dietrich said they released another spider, which is a natural predator of the brown recluse, into the building.

“It is exceedingly difficult to get rid of (brown recluses) in a building, so that makes it a good thing that the hype is bigger than the spider in many cases,” Nixon said.