Washington State is home to a wide array of spider species. While encountering spiders can sometimes cause apprehension, the vast majority of these arachnids are harmless to humans. Spiders play a beneficial role in the local ecosystem, primarily by controlling insect populations. Understanding the common spiders in the region can help foster appreciation for their presence and reduce unnecessary concern.
Commonly Encountered Spiders
Many spiders frequently observed in Washington State are not considered dangerous to humans. Orb weaver spiders, for instance, are known for constructing large, intricate circular webs. Their appearance varies, with some featuring distinct markings. Orb weavers remain in their webs, waiting for prey, and are generally docile.
Common house spiders (Parasteatoda tepidariorum) are another frequent sight, often building tangled webs in corners of homes. These spiders are brown or gray with darker markings and are small, less than a quarter-inch long. Jumping spiders (Phidippus audax) are small, compact spiders with excellent eyesight, often seen actively hunting insects during the day. They are characterized by their stout, hairy bodies and a distinctive pair of large, forward-facing eyes.
“Daddy long-legs” commonly refers to two different arachnids: cellar spiders (Pholcus phalangioides) and harvestmen (Phalangium opilio). Cellar spiders are true spiders with long, thin legs and construct irregular webs in undisturbed areas. Harvestmen, while also arachnids with long legs, are not spiders, as their body segments are broadly fused, and they do not produce silk or venom. Both are harmless to humans and contribute to pest control.
Spiders Requiring Caution
While most spiders in Washington are innocuous, two species warrant caution due to their medically significant venom: the Western Black Widow and, to a lesser extent, the Yellow Sac Spider. The Western Black Widow (Latrodectus hesperus) is primarily found in eastern Washington, though small populations exist in western areas. Adult females are identifiable by their shiny black body, approximately half an inch long, and a red or yellowish-orange hourglass marking on the underside of their abdomen. They prefer dark, undisturbed locations such as woodpiles and under eaves, where they build tangled webs. A bite from a female black widow can cause severe pain, muscle cramping, and abdominal discomfort due to its neurotoxic venom, necessitating medical attention, especially for vulnerable individuals.
The Hobo Spider (Eratigena agrestis) is another species found throughout Washington State, known for building funnel-shaped webs in dark crevices. These spiders are light to medium brown, measuring about 1 to 1.75 inches, and lack distinct color patterns on their legs. While once widely considered dangerous, current scientific understanding indicates that hobo spider bites are not as medically significant as previously believed, with no evidence linking their venom to necrotic wounds in people. They are generally shy and reluctant to bite unless threatened or trapped.
Another spider sometimes noted for medically significant bites is the Yellow Sac Spider (Cheiracanthium species), found in Washington. These spiders are small, about a quarter to half an inch long, and can be yellow, white, or greenish, with darker markings. Yellow sac spiders are active hunters that do not build webs for prey capture, and their bites, though painful and sometimes causing localized reactions, are generally not life-threatening.
Identifying Spiders
Identifying spiders can be approached by observing several general characteristics. Body shape and size offer initial clues; some spiders have robust, compact bodies, while others appear more delicate or elongated. Leg length and the presence of hairiness can also differentiate species. For instance, jumping spiders have relatively short, stout legs, while cellar spiders possess remarkably long, slender ones.
Web type provides a significant diagnostic feature, as different spider families construct distinct web architectures. Orb webs are the classic circular, wheel-shaped designs, typically spun by garden spiders. Funnel webs, in corners or dense vegetation, lead into a silken tube where the spider waits. Tangled or cobwebs are irregular silk structures usually associated with common house spiders and black widows.
While eye arrangement can be a precise identification tool, most spiders have eight simple eyes, and their specific patterns are often too subtle for the average observer. When observing spiders for identification, it is prudent to do so from a safe distance without direct handling, perhaps by using a clear container to temporarily capture them for a closer look before release.
Living Alongside Spiders
Coexisting with spiders in Washington State involves understanding their habits and implementing simple management strategies. To prevent spiders from entering homes, sealing cracks and gaps around homes is an effective measure. Reducing clutter indoors and outdoors, such as firewood piles and dense shrubbery near the house, eliminates potential hiding and breeding spots. Maintaining a clean environment by regularly vacuuming and dusting also helps remove webs and egg sacs, discouraging spider populations.
If a spider is found indoors, safe removal is a straightforward process. A common method involves placing a glass or cup over the spider, sliding a piece of paper underneath, and then releasing it outdoors. Spiders are beneficial predators, consuming insects and other pests, thus contributing to natural pest control. Recognizing their ecological value and understanding that most species pose no threat can help foster a more comfortable relationship with these often-misunderstood creatures.