Mediterranean recluse spiders have been identified in the basements and remote areas of several Ann Arbor campus buildings due to a decrease in building occupancy. Those buildings are being treated by U-M Pest Management.

The Mediterranean recluse spider is a cousin to the brown recluse and are even more reclusive than the feared brown recluse spider. 

“As the name implies, they are reclusive and bites are extremely rare,” said Anne Danielson-Francois, associate professor of biology at UM-Dearborn’s College of Arts, Sciences and Letters. “Mediterranean recluse spiders prefer basement spaces, tunnels and other hideaways where there is a decrease in foot traffic. 

An adult male Loxosceles rufescens, also known as a Mediterranean recluse spider.
An adult male Mediterranean recluse spider. (Photo courtesy of UM-Dearborn)

“Users browsing the library stacks would be very unlikely to encounter a stray spider or be bitten.” 

Most recently, a small number of recluse spiders were found in a basement mechanical room of the Shapiro Library. The spiders were discovered during a routine building check by Pest Management in late January. 

“A misunderstanding of the situation led the library to close for two days,” says Kim Broekhuizen, university spokesperson. “Based on what we all know now, library managers agree that it was a mistake to close the building and they apologize for the inconvenience to the university community.”

Danielson-Francois worked with the university to determine the identity of the spider species after examining samples provided by U-M Pest Management that were found in traps.

Pest Management has been conducting weekly inspections of buildings where the spider has been identified. Monitoring of the identified buildings continues with chemical pesticide treatment applied per industry standards.

In addition, Pest Management has been inspecting and treating all tunnels on campus where these spiders have been found.

Building occupants affected by the spiders have been notified and have been asked to partner with the Pest Management team to safely clean out storage rooms, maintenance or mechanical rooms and custodial closets to combat the spiders.

Safety precautions for those working in basement areas include: wear a long-sleeved shirt, hat, gloves, and boots or shoes which enclose the entire foot, when handling stored items, cardboard boxes, lumber or rocks.

Anyone who sees one of the spiders is asked to contact the Pest Management team at 734-647-2059.

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