Washington State hosts a diverse array of spider species, many commonly encountered in and around homes. While their presence can cause apprehension, most spiders in the region are harmless to humans and play an important role in controlling insect populations. Understanding these arachnids helps residents coexist and distinguish between beneficial species and those that warrant more caution.
Common and Harmless Spiders
Among the most frequently observed spiders in Washington is the Giant House Spider (Eratigena atrica), a large arachnid that can reach up to four inches in leg span. These spiders are typically brown with gray markings and are often found indoors in dark, undisturbed areas like basements and garages, particularly during late summer and fall as males search for mates. Despite their intimidating size and rapid movements, Giant House Spiders pose no medical threat to humans.
Wolf Spiders (Lycosidae family) are another common sight, identifiable by their robust, hairy bodies, usually black, brown, or gray with various markings. These agile hunters do not build webs to catch prey but actively pursue insects on the ground in diverse habitats, including woodlands, gardens, and grassy fields. Female wolf spiders carry their egg sacs on their spinnerets and later allow spiderlings to ride on their backs for several days after hatching. Although large and fast, Wolf Spiders are not aggressive, and their bites, if provoked, cause only minor, temporary symptoms.
Orb Weavers (Araneidae family) are recognized by the intricate, circular webs they construct, often spanning several feet in diameter. These colorful spiders, frequently orange or brown with long legs, are common in gardens, forests, and around building eaves, especially during summer. Orb weavers are not aggressive, rarely bite, and their venom is not toxic. They are beneficial for controlling insects.
Cellar Spiders (Pholcidae family), often called “daddy longlegs” due to their extremely long, thin legs, are pale yellow, gray, or light brown. They build messy, irregular webs in dark, secluded, and damp areas such as basements, cellars, and garages. These fragile spiders are harmless and not known to bite; they feed on small insects and other spiders.
Spiders of Medical Concern
While most spiders in Washington are harmless, two species have venom of medical significance: the Western Black Widow and the Yellow Sac Spider. The Western Black Widow (Latrodectus hesperus) is identifiable by its shiny black body and a distinct red or orange hourglass marking on the underside of its abdomen. Adult females, typically about a half-inch long, possess harmful venom, though bites are rare and usually occur when threatened or guarding eggs.
Black widows prefer dark, undisturbed locations like woodpiles, meter boxes, under eaves, and cluttered areas in basements or crawl spaces, where they build messy, irregular webs. A bite may initially feel like a pinprick or go unnoticed, but symptoms develop within 30 minutes to a few hours. Common reactions include intense muscle pain and cramping, particularly in the abdomen, back, and chest, along with muscle stiffness, nausea, vomiting, headache, and sweating.
If a black widow bite is suspected, wash the bite area with soap and water and apply ice to reduce swelling. Medical attention should be sought immediately, especially for young children, the elderly, or individuals with existing health conditions. Bringing the spider for identification can aid in treatment.
The Hobo Spider (Eratigena agrestis) is a brown spider with an oblong abdomen that may have yellowish markings and solid light brown legs without bands. While once believed to cause necrotic wounds, current scientific understanding, supported by the CDC, confirms Hobo Spider venom is not toxic to humans. Hobo spiders are shy, reluctant to bite unless trapped, and are found throughout Washington in funnel-shaped webs near the ground, often in holes and cracks. Bites are rare and may cause minor skin irritation, redness, and pain, but serious symptoms are not associated with them. If any bite leads to symptoms like increasing pain, blistering, nausea, or cognitive issues, medical consultation is advisable.
Identifying Spiders and Managing Encounters
Identifying spiders involves observing key features like body shape, leg length, markings, and web type. For instance, a large, circular web suggests an orb weaver, while a messy, funnel-shaped web might indicate a giant house spider. Knowing a spider’s typical habitat can also provide clues; cellar spiders prefer damp, secluded areas, whereas wolf spiders are ground dwellers.
When encountering spiders in the home, safe removal methods are preferred over extermination. Spiders can be gently captured using a cup and a piece of paper, then released outdoors.
To discourage spiders from entering or residing indoors, several preventive measures can be taken. Seal small cracks and openings around windows, doors, and foundations with caulk to block entry points. Reduce clutter in basements, garages, and other undisturbed areas to eliminate hiding spots. Regular cleaning, including vacuuming around corners, furniture, and along ceiling and floor edges, helps remove webs and egg sacs. Maintain outdoor areas by keeping woodpiles, rock piles, and dense shrubbery away from the house’s exterior to reduce potential outdoor habitats near entry points.