Researchers at the Oregon Poison Center at Oregon Health & Science University hope to better understand spider bites in the Northwest.

They are trying to determine which spiders bite, which cause skin loss (ulcers) — and whether the much-maligned hobo spider causes either, according to a press release.

Evidence directly linking spider bites to ulceration or infection is thin, so say OHSU researchers. People often find red marks on their skin and attribute them to spider bites.

The Northwest native hobo spider has been implicated as a source of ulcers and skin infections for many years. Its venom has been demonstrated to cause tissue death when injected into the skin of animals, but there is debate about whether the spider ever bites or is even capable of biting humans.

“There isn’t a single documented case of actually seeing a hobo spider bite a human that resulted in ulceration,” said Dr. Rob Hendrickson, the study’s principal investigator.

Hobo spiders have been presumed to be the only spider in the Northwest capable of causing ulceration. Presumptions, however, aren’t factual science.

The Oregon Poison Center is helping in the project, asking all Oregonians who actually see a spider bite them to call (800) 222-1222. Poison center staff will offer medical advice as usual and then make follow-up calls during the next several weeks to check for signs of ulceration and infection. The caller also will be sent a postage-paid package in which to send the spider to the poison center.

“We understand not everyone will feel comfortable killing the spider, and we won’t pressure them to do so, but we would still like to hear about the spider bite,” said OHSU’s  Nathanael McKeown.