The question of whether dangerous spiders exist in Washington State often causes confusion, partly due to the difference between venomous and poisonous creatures. Spiders are venomous, meaning they inject toxins through a bite, unlike poisonous creatures which release toxins when ingested or absorbed. In Washington, almost all spiders possess venom, but only a few species have venom considered medically significant to humans. The state has a very low risk profile for serious spider bites, and the vast majority of species found are harmless.
The Medically Significant Spider in Washington
The single spider species in Washington State whose bite is a genuine medical concern is the Western Black Widow (Latrodectus hesperus). The adult female is easily recognizable, presenting a glossy black body with a round abdomen. Her defining feature is the bright red or reddish-orange hourglass shape located on the underside of the abdomen.
The female typically measures about half an inch in length, excluding her legs, while the male is much smaller and poses no threat. Black Widows build irregular, tangled webs, often placed in dark, undisturbed locations close to the ground. Common habitats include woodpiles, outdoor sheds, crawlspaces, water meter boxes, and cluttered garages.
The female Black Widow’s venom contains a neurotoxin called alpha-latrotoxin, which affects the victim’s nervous system. A bite results in Latrodectism, with symptoms including severe muscle pain, cramping, and rigidity, often felt in the abdomen, back, and chest. Other systemic symptoms can involve nausea, vomiting, localized sweating, and headache, typically beginning within an hour. Though the bite is painful, fatalities are extremely rare, particularly with modern medical care.
Debunking the Brown Recluse Myth
The Brown Recluse spider (Loxosceles reclusa) is the subject of much concern but does not have established populations in Washington State. Its native range is confined to the central Midwest and Southern United States, and the state’s climate is unsuitable for it to thrive. Despite this, many reported “recluse bites” in the Pacific Northwest are almost certainly misdiagnoses.
A true Brown Recluse bite can cause a necrotic lesion, or tissue death, but such wounds in Washington are overwhelmingly caused by other conditions. Medical professionals often attribute non-spider-related skin lesions, such as those from Methicillin-resistant Staphylococcus aureus (MRSA) bacterial infections, to a recluse bite. It is safe to conclude that any spider found in the state, even if it resembles a recluse, is not this medically dangerous species.
Common Spiders That Cause Alarm
Many spiders in Washington frighten people because of their size or speed, leading to misidentification as a threat. Two of the most common are the Hobo Spider (Eratigena agrestis) and the Giant House Spider (Eratigena atrica). Both species are brown, build funnel-shaped webs, and are frequently seen indoors, particularly during the late summer and fall as males roam in search of females.
The Hobo Spider was once mistakenly believed to cause necrotic skin lesions similar to the Brown Recluse, earning it an undeserved reputation. Current scientific consensus indicates that the Hobo Spider’s venom is not medically significant to humans. The Giant House Spider is one of the largest spiders in the state, with a leg span that can exceed three inches, and is known for its speed, but it is harmless. Both species are reluctant to bite and generally only do so when trapped against the skin.
Emergency Action and Habitat Avoidance
If a bite from a Black Widow or any other spider is suspected, clean the bite area thoroughly with soap and water. Applying a cold compress or ice pack can help to reduce swelling and slow the spread of any venom. Seek medical attention if the pain is severe, symptoms begin to spread, or if the victim is a child or elderly individual.
For identification purposes, if it is safe, capture the spider in a jar or container, but never attempt to handle it directly. To reduce the chance of encountering spiders indoors, eliminate potential habitats around the home.
Avoidance Measures
To minimize spider encounters, focus on habitat reduction and blocking entry points:
- Regularly clear woodpiles, debris, and clutter from outdoor areas near the foundation to remove nesting sites.
- Seal cracks and crevices in the foundation and around windows and doors to block entry points.
- Shake out shoes and clothing stored in garages, sheds, or basements before wearing them, as spiders may seek shelter there.