Oregon is home to over 500 known spider species across the state’s varied landscapes. The vast majority of these residents are small, shy, and entirely harmless to humans. Spiders play an important role in the local ecosystem, serving as beneficial natural controllers of insect pests in yards and homes. This overview focuses on the most frequently encountered species to help residents understand which ones pose a health risk.
Medically Significant Spiders of Oregon
Only one spider species in Oregon is considered to have venom that is medically significant: the Western Black Widow, Latrodectus hesperus. The adult female is the most recognizable and potentially harmful, featuring a shiny black body with a distinctive red or reddish-orange hourglass marking on the underside of her rounded abdomen. These spiders are not aggressive and will bite only when disturbed or accidentally trapped, such as when a person reaches into a woodpile or puts on a shoe where the spider is hiding.
The Western Black Widow prefers quiet, dark, and sheltered outdoor spaces like woodpiles, sheds, crawl spaces, and meter boxes. While present throughout Oregon, they are most commonly encountered in the drier, warmer regions of Southwestern and Eastern Oregon. A bite delivers a neurotoxic venom that can cause severe muscle pain, cramping, abdominal rigidity, and nausea. Fatalities are extremely rare, especially with prompt medical treatment.
A common misconception is that the Brown Recluse spider, Loxosceles reclusa, is established in Oregon, but official sources confirm this is not the case. The native range of the Brown Recluse is limited to the south-central United States. The climate of the Pacific Northwest is generally unfavorable for them to establish self-sustaining populations. Many bites mistakenly attributed to the Brown Recluse are often caused by other common spiders or entirely different medical conditions.
Common Spiders Found Inside Homes
The spiders most commonly encountered inside Oregon homes are generally harmless introduced species that seek shelter in basements, corners, and garages. The Giant House Spider, Eratigena atrica or Eratigena duellica, is one of the largest spiders in the region, known for its impressive leg span that can exceed four inches. Despite its intimidating size, this spider is not dangerous to humans, and its presence helps control other insects. It often builds large, messy, funnel-shaped webs in undisturbed areas like crawl spaces and dark corners.
The Hobo Spider, Eratigena agrestis, is another funnel-web weaver frequently found indoors, particularly during the late summer and early fall when males wander in search of mates. Historically, the Hobo Spider carried a reputation for having venom that could cause necrotic lesions, but modern research has largely debunked this claim. Its bite typically results in only mild, localized pain and redness.
Cellar Spiders, members of the Pholcidae family, are often mistaken for the unrelated harvestman, sharing the common name “daddy long-legs” due to their extremely long, thin legs. These pale spiders hang upside down in their messy, irregular cobwebs, continuously adding to them in damp, dark corners. Cellar spiders are beneficial inside the home because they prey on a variety of other household pests, including other spiders, flies, and mosquitoes. They are not known to bite humans.
Notable Outdoor Spiders and Their Habitats
Moving outside the home, Oregon’s natural areas are populated by active hunters and skilled web-builders that play a visible role in garden and forest health. Orb Weavers, such as the colorful Cross Orbweaver, are responsible for the large, circular webs often seen strung between tree branches or across garden paths. These intricate webs, which can measure several feet in diameter, are rebuilt daily to efficiently capture flying insects like moths and mosquitoes. Orb Weavers are docile and non-aggressive.
Wolf Spiders, belonging to the family Lycosidae, are large, hairy, ground-dwelling spiders that use speed and excellent eyesight instead of webs to catch their prey. They are often seen running across lawns or trails, actively stalking and pouncing on insects. Female Wolf Spiders exhibit a unique maternal behavior, carrying their egg sac attached to their spinnerets and later allowing the hatched spiderlings to ride on their backs.
Jumping Spiders, from the family Salticidae, are small, stocky, and diurnal hunters with remarkable, large, forward-facing eyes that grant them exceptional vision. Rather than building webs for capture, they stalk their prey with a curious, jerky movement and then pounce with precision. Several species, like the Bold Jumping Spider, are common in Oregon gardens, fences, and walls. These active predators are completely harmless to people.