Fact vs. Fiction: Northern Yellow Sac Spiders

Fiction: Most spider bites are from brown recluse spiders.
Fact: Northern yellow sac spiders (Cheiracanthium mildei) are responsible for more bites than any other spider and are frequently misdiagnosed as brown recluse spider bites.

Fiction: It’s almost impossible to tell a sac spider bite from a brown recluse bite.
Fact: Both bites will be reddish, with mild swelling and bee-sting-like pain. The main difference is a recluse bite takes two to three months to heal; sac spider bites will heal in days or weeks. Without capturing the spider in the act of biting, it’s almost impossible to diagnose the species of the bite by looking at the wound.

Fiction: Yellow sac spiders are dangerous to humans because their bite will cause parts of the human body to fall off.
Fact: In several studies in which the spider and bite were positively verified, no necrosis occurred. Sadly, some medical and other publications continue to perpetuate the myth that sac spider bites are dangerously necrotic, based on anecdotal or unverified bite reports. Herpes sores, staph infections, methicillin-resistant Staphylococcus aureus (MRSA), dermatitis and a host of other skin lesions are frequently misdiagnosed as spider bites.

Fiction: Yellow sac spider webs are difficult to get rid of.
Fact: Sac spiders are nocturnal hunters that don’t build webs. They create silken sacs (hence the name) used for daytime shelter. After laying their eggs, the females cover them with a silken case. Indoors, these typically are found on walls and ceilings. In 2011, Mazda found them clogging the fuel ventilation systems of Mazda6 cars. The manufacturer recalled 65,000 vehicles built between 2009 and 2010. Even today, nobody is quite sure why the webbing wasn’t found in other models built at the same plant or in other makes of similar cars. pmp

You can reach the McGoverns at jeffreymcgovern@mindspring.com