September 26, 2023

Late last month, Anne Danielson-Francois, Associate Biology Professor at the University of Michigan, received an unusual package. She had instructed the sender to make sure the contents – spiders – were padded because she didn’t want her legs to break off.

When Dr. Danielson-Francois opened the little brown box and they were there – a male spider clinging to a glue trap, two female spiders suspended in an alcohol solution, and a few juvenile spiders.

Dr. Danielson-Francois, who works on the university’s Dearborn campus, was hired by university officials as a kind of spider buster. Last month, pest control teams discovered unknown spiders had moved into the basement of the Shapiro Undergraduate Library on the Ann Arbor campus, a room that was less crowded due to the coronavirus pandemic, the university said.

Your task: Identify the arachnids and report back.

Dr. Danielson-Francois usually examines another type of spider, a giant nephila, or a spider that weaves orbs. But she examined the man’s dehydrated body, examined his genitals, consulted taxonomic literature, noted his six eyes and came to the conclusion: Mediterranean spiders populated the library basement.

Their body length can be up to half an inch, and their leg span can be up to an inch, about as large as half a dollar. And in the rare event that they bite someone, tissue necrosis or skin death can result.

In response to the infestation, the library, which was only open by appointment, closed on Sunday and Monday to deal with the spiders.

The university issued a statement Tuesday announcing the discovery of the arachnids, stating that solitary spiders in the Mediterranean are even more solitary than their U.S. cousins, brown recluse spiders. Given the low risk posed by the spiders, the university said the decision to close the library was “a misunderstanding of the situation”.

“From what we all now know, the library administrators agree that closing the building was a mistake and they apologize for the inconvenience to the university community,” said Kim Broekhuizen, a spokeswoman for the university statement published on the university website.

The pest control team treated the buildings’ tunnels with pesticides, cleaned up isolated rooms, and asked people to report further sightings.

Some spiders have also been found in the Stearns building on the university’s north campus, the student newspaper The Michigan Daily reported this week. Ms. Broekhuizen said lone spiders were found in about a dozen academic buildings on Ann Arbor’s campus, which includes about 300 buildings. None were found in dormitories.

“Due to the pandemic, these are almost all of the low-occupancy buildings as the university prioritized social distancing, decreased density and increased cleaning in all of our facilities,” she said in an email on Thursday.

Recluse spiders are aptly named. They like to be alone and generally stay away from places where there is pedestrian traffic. Instead, they crawl around basements or anywhere they can find a crack.

Dr. Danielson-Francois said in an interview on Thursday that people are unlikely to encounter them, “unless you are the unfortunate plumber who has to go to a crawl space.” If they bite, she said, “it might be a dry bite.”

“They don’t see you as prey,” she added. “They don’t want to consume you. It’s more of a defense. “

The episode caused slight tremors on campus. Students commented on coverage from The Michigan Daily on the Overheard at UMich Facebook page. “This is insane lol,” wrote one student. “I’m glad I’m not going to campus.”

The University of Michigan library attempted to address concerns, saying in a statement Tuesday that another spider was just caught that day at the Shapiro Undergraduate Library, but that “its presence in a mechanical room poses no risk to library users “.

The discovery was similar to other cases during the pandemic, when creatures moved in when people moved out of buildings because of orders to stay home.

“People worry when it comes to hermits – there is a lot of fear there,” said Dr. Danielson-Francois. “But if you rummage through the library stacks, it’s so unlikely that you will come across any of those spiders.”

Recluse spiders are common but not widespread in the United States, said Richard S. Vetter, a retired research fellow at the University of California at Riverside who is one of the country’s foremost experts on recluse spiders.

“You can overcrowd this building, but go to the next building and there are no hermits,” he said. “A few buildings in every state doesn’t mean they are widespread and causing damage.”

Skin lesions are often misdiagnosed as being caused by spider bites, he said, noting that a brown solitary spider bite can potentially lead to a “very, very, very rare” fatal case. “We talk a few bites a year,” he said.

He added that the fear of spiders is often irrational. “They have many legs, they move quickly, they are hairy, they have many eyes and they show up unexpectedly,” he said. “They just look different and act differently.”