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Spiders in the Northwest 

Revisiting hobos, widows and violins

Left, a dead brown recluse from Kansas, also known as a violin spider. Photo courtesy of Sam Anderson. At right, female adult hobo spider. Photo by Jim Anderson.

Left, a dead brown recluse from Kansas, also known as a violin spider. Photo courtesy of Sam Anderson. At right, female adult hobo spider. Photo by Jim Anderson.

Judging from the phone calls, emails and text messages, things have gotten out of hand in the spider world, especially regarding those thought to be dangerous. Hence, right from the get-go, let's put the real "Bad One," the brown recluse, also known as the violin spider—behind us.

One, it does not and cannot live in the Northwest. Two, if one is ever found here, it was transported from the Southwest, Kansas, or Texas, etc. The brown recluse is very distinctive; the violin-shaped marking on the carapace (lid on the front body part) is so plain to see it would be hard to miss it and even the juveniles sport that distinctive mark. Yes, this is a very deadly spider. The bite from a female violin/recluse spider can cause excruciating pain and severe necrosis in human flesh.

That leaves us the only native spider that can do any real damage: the black widow. Stumbling into a black widow's web, the web is so strong it actually crackles when broken. The black widow is black and she has a bulbous abdomen (hind end), and very long legs. Don't go looking for the red hour glass, young females don't have it, but she can still administer harmful amounts of venom (NOT poison). Yes, there is a male in that group, he's black, harmless and doesn't sport an hour glass, but has red and white stripes on his back instead. He does have two large boxing glove-like appendages between his front legs in which he stores sperm.

Now we get to the infamous hobo spider, (Tegenaria agrestis) a member of the genus known colloquially as funnel web spiders. The hobo spider is one of a small number of spiders whose bites are generally considered to be "medically significant," but the science for that quote is sadly lacking. The tale that gives the "hobo" its common name comes from the assumption that this spider spread to distant cities via railways.

There are hundreds of species found in the hobo spider tribe, and it's virtually impossible to tell them apart from a photo, or sometimes, even a close look by an expert arachnologist. The hobo was first described in 1802 by naturalist C.A. Walkenaer, under the name Aranea agrestis, in reference to its western European habitat of fields, woods and under rocks.

It was first reported in the US in 1936 by arachnologist Harriet Exline (as Tegenaria magnacava) in Seattle. There, without the widespread presence of any dominant competitors, it rapidly adapted to living in urban areas, where it became abundant and extended its range. By 1968 it had become established as far east as Spokane, and Moscow, Idaho, south to Oregon and is reported throughout California.

In the United States, the hobo spider got the reputation as a dangerous species based on a toxicology study on rabbits where lesions appeared after spiders were induced to bite the rabbits. The Center for Disease Control (CDC) and other U.S. government agencies also used this same study as the basis for a report claiming that the hobo spider bite causes necrosis in humans, despite the absence of any confirmed cases.

I can't tell a hobo spider from our common grass spider, which cannot cause humans any medical issues, but can often scare the daylights out of anyone with an acute fear of spiders. I've heard the cry all too often, "LOOK! It's a hobo spider!"

Funnel web spiders construct a silk sheeting and lie in wait, out-of-sight at the small end of the funnel for some arthropod prey to blunder onto their webs. We often find them in or around windows, in the barn, garage, or behind washing machines, my computers and book shelves.

Some people love the idea of a spider being dangerous, if not fatal upon contact, but the toxicity and aggression of the hobo spider are currently disputed by arachnologists. If a female hobo spider is tending an egg sac, it may become aggressive if it perceives a threat. However, they generally do not bite unless forced to protect themselves. I had to force a sheet web spider to bite me, and all that happened was my hand fell, not really; I didn't even swell up.


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