Spider in Camas, Washington; Black with white legs

[trgiles]

Hi, found this little spider in our bathroom this morning. I'm thinking it came in through the open window. I have never seen one like it before. Any ideas what it is?

[Eric]

trgiles:

Very nice image! The spider is a male running crab spider, Philodromus dispar. This is a European species that has been established in the Pacific Northwest for many decades. Females look much different (entirely pale brown with darker markings). We may want to use your image (with your permission) to illustrate this species in a guide page.

These spiders do not spin webs, but wander in search of prey. They occasionally stray indoors but pose no known threat to people or pets.

Eric

[trgiles]

Thanks! We are new to this area and I am trying to learn about all of the different spiders that I find. With two little kids I am hoping that none of the spiders I find are dangerous I'm sure I will be posting more pics throughout the summer. Feel free to use the image!

Tracy

[Ungoliant]

With two little kids I am hoping that none of the spiders I find are dangerous :)

Fortunately, we don't have many dangerously venomous species in the U.S., so if you are interested, you should be able to learn to recognize the few that are.

Widow Spiders (Latrodectus)

The first medically significant genus is the widow spider (Latrodectus). There are five species of widow spiders in the U.S. However, only one species is normally found in Washington: the western black widow (Latrodectus hesperus).

With widow spiders, it's the bite of the adult female that is medically significant, so that is what I would concentrate on learning to identify. (Adult males and juveniles of both sexes are considered harmless.) The female western black widow resembles the infamous southern black widow (Latrodectus mactans). She has a dark brown or black body with a large, round abdomen. There is a red or orange hourglass-shaped marking on the underside of her abdomen. The bodies of mature females are usually shiny and dark. The back of the abdomen is unmarked except for a reddish spot at the tip.

These spiders are reclusive and would rather flee than fight. They can, however, bite in self-defense if molested, pinched, or squeezed. Although a black widow's bite can be an excruciating experience, fatalities in healthy adults are extremely rare, especially since the advent of antivenom. However, you should always seek medical attention if bitten by a widow spider (and if possible, capture the spider for identification).

Note: some spiders, such as the false black widow (Steatoda grossa), can be mistaken for widow spiders. You can usually distinguish between true widows and false spiders by the markings (or lack thereof) on their bodies. Most of these spiders are harmless. However, the bite of the false black widow can produce symptoms that are similar to those of a true widow spider (but much less severe).

Recluse Spiders (Loxosceles)

The second medically significant genus is the recluse spider (Loxosceles). You don't need to worry about this genus, because recluse spiders don't live in Washington. (See this map of the distribution of U.S. recluse species.)

For those who do live in areas with recluse spiders, it is easy to learn to identify them. Contrary to popular belief, the dark violin-shaped marking on the back of the cephalothorax (the first half of the spider's body) is not the best way to identify these spiders. Many spiders dark marks on their backs that people imagine to be violin-shaped. (And many other people see violin-shaped marks on other parts of the spider's body.)

The best way to identify recluse spiders is by the arrangement of its eyes. Unlike most other spiders, recluse spiders have three pairs of eyes that are arranged in a triangle. Most other spiders have eight eyes, and the other six-eyed spiders have different arrangements. (Only one other family has eyes like a recluse: the harmless spitting spider. However, spitting spiders are easily distinguished from recluse spiders.) "How to Identify and Misidentify a Brown Recluse Spider" by Rick Vetter has more detailed information, including photos of spiders that are commonly mistaken for brown recluses.

Brown recluse bites can produce necrotic lesions, but few people are bitten, and most bites heal without serious complications. There are no known fatalities.

See also: "Things You Can Do to Reduce the Chances of Being Bitten by a Brown Recluse Spider" and "Causes of Necrotic Wounds Other Than Brown Recluse Spider Bites."

Hobo Spiders (Tegenaria agrestis)

Hobo spiders can be found in Washington, but contrary to popular belief, these spiders are not recognized by the scientific community as being dangerously venomous. (It's interesting to note that in Europe, where this spider is originally from, hobo spiders are regarded as harmless.) For more information about the alleged toxicity of hobo spider bites, see the remarks on the BugGuide article and Rod Crawford's section on hobo spider myths.