Are Hobo Spiders as Dangerous as People Think?

Hobo spiders (Eratigena agrestis) are not as dangerous to humans as once believed; confirmed cases of necrotic bites attributed to them are extremely rare and the bulk of peer-reviewed research does not support the claim that their bites routinely cause severe tissue damage. Early reports linking hobo spiders to necrotic lesions in the 1990s prompted widespread concern, but subsequent toxicological, clinical, and epidemiological studies have failed to reproduce those findings or demonstrate a consistent pattern of medically significant reactions.

This clarification matters for Pacific Northwest homeowners because the hobo spider is established across much of the region and commonly occupies basements, crawl spaces, woodpiles, and other sheltered, cool, and damp microhabitats favored by the local climate. Seasonal movement into homes—especially in late summer and autumn—combined with frequent misidentification of similar local species means encounters are common and anxiety high. A realistic appraisal of actual medical risk helps inform appropriate prevention, diagnosis, and response without relying on outdated or exaggerated claims.

 

Are hobo spiders common in Seattle and the Pacific Northwest

The hobo spider (formerly Tegenaria agrestis, now often placed in the genus Eratigena) is an established, non‑native species in the Pacific Northwest and is encountered regularly in western Washington and Oregon. Adult female body lengths typically range from about 7–14 mm and males 6–9 mm (not including legs), so they are medium‑sized compared with larger native wolf spiders. Their established range in the region centers on low‑elevation urban and suburban areas—coastal lowlands and river valleys—where they have been present since their introduction to North America in the 20th century.

In the Seattle area hobo spiders are encountered most often inside human structures rather than out on exposed wet foliage. Funnel webs can span roughly 10–50 cm across with a tubular retreat 2–6 cm deep tucked into corners along foundation walls, basement sills, garages and cluttered storage areas; outdoors they prefer dry rock or wood piles and the sheltered undersides of debris. Seattle’s maritime climate (annual precipitation roughly 900–1,000 mm and frequent winter dampness) produces wetter outdoor microhabitats that favor other spiders, so hobo populations tend to persist in the drier microclimates created by heated basements, crawl spaces and garages.

Seasonal patterns in the PNW affect how commonly people see them: adults are most noticeable from late spring through early fall, with male wanderings peaking in late summer and early fall (August–October) as males leave retreats to search for mates. Females remain largely sedentary in their funnels, often overwintering as adults in sheltered locations; under sheltered indoor conditions females can survive for one to two years, while males usually die soon after the fall mating period. These life‑cycle details explain why homeowner reports rise in late summer and fall even if outdoor observations remain infrequent.

Despite being established, hobo spiders are only one of several funnel‑weaver and ground‑dwelling spiders PNW homeowners see. Grass spiders (Agelenopsis and relatives) build larger, more horizontal sheet‑plus‑funnel webs in lawns and low vegetation, often 30–60 cm across, and have lighter longitudinal striping; wolf spiders (Lycosidae) are active hunters with no web, much bulkier bodies (often 10–30+ mm), and different habits. In Seattle homes, therefore, hobo spiders are common enough to be a regular indoor species but are frequently confused with these other, sometimes more numerous, local spiders.

 

Can hobo spider bites cause necrosis or serious illness in people in this region

Hobo spiders were widely blamed in the Pacific Northwest in the 1990s for necrotic skin lesions, but by the 2000s multiple clinicopathological reviews and experimental studies had overturned that view. Controlled laboratory work and clinical case series published in the 2000s (including reviews led by Vetter and clinical assessments by Isbister and colleagues) found no reproducible dermonecrotic effect in mammalian models at doses comparable to those a human would receive in a typical bite. In short, the historical association between hobo bites and progressive necrosis in the PNW does not hold up to the published evidence accumulated since the late 1990s.

Typical symptoms from a confirmed hobo spider encounter differ from the progressive necrosis attributed to Loxosceles (brown recluse) envenomations. A hobo spider puncture wound, when present, is generally a 1–3 mm paired puncture; local pain or paresthesia may appear immediately and local erythema or mild swelling will usually peak within 24–48 hours. By contrast, true recluse bites classically progress over days to weeks, often developing central pallor and expanding necrosis that can reach 1–10 cm over 1–3 weeks. Reports of rapidly enlarging, clearly necrotic lesions in Seattle-area patients have typically been reclassified after culture or biopsy as bacterial cellulitis, MRSA, vascular ulceration, or other non-spider causes.

Toxicology and prey-response data help explain the discrepancy: hobo spider venom shows clear insecticidal activity (paralysis in arthropod prey within minutes at microliter-scale doses) but the same venom has low cytotoxicity in mammalian tissue assays and has failed to produce dermonecrosis in standard lab mammal tests at realistic exposure levels. Clinical literature from the PNW includes very few—and poorly documented—cases that could be credibly attributed to hobo envenomation; when the biting specimen was not captured and reliably identified, diagnostic certainty drops sharply. Thus the weight of evidence is that hobo venom can irritate human skin in some people but is unlikely to cause the progressive tissue necrosis once ascribed to it.

In the Seattle climate—cool, maritime, with median annual humidity high and frequent basement dampness—spiders are common in basements and around foundations, which led to abundant encounters and misattributions in the 1990s. From a clinical standpoint, a rapidly worsening ulcerative lesion in this region that enlarges over 48–72 hours is statistically more likely to be an infected wound or an underlying dermatologic condition than a primary hobo-spider dermonecrosis. When clinicians have needed diagnostic confirmation in the literature, they have relied on wound cultures, histopathology, and capture/identification of the offending specimen; without those, definitive attribution to hobo spider venom remains unsupported by the modern evidence base.

 

How to identify hobo spiders and tell them apart from wolf spiders and grass spiders in the PNW

Adult hobo spiders (Eratigena agrestis) in the Pacific Northwest typically have a body length in the rough range of 6–14 mm, with overall leg spans commonly reaching 20–30 mm; that size is similar to many grass spiders but usually smaller and slimmer than many local wolf spiders, which commonly have body lengths of 10–35 mm and leg spans that can exceed 40 mm in larger species. A reliable morphological difference is the posterior spinnerets: agelenids (hobos and grass spiders) have long, cylindrical posterior spinnerets that are often visible extending past the end of the abdomen when viewed closely, whereas wolf spiders (Lycosidae) have much shorter, less conspicuous spinnerets. In hand-lens examination the eye patterns also differ — agelenids show eight eyes arranged in two more-or-less horizontal rows of four, while wolf spiders display a distinctive set of enlarged anterior median eyes (the big front-facing pair) above a row of four smaller posterior eyes, giving wolf spiders noticeably better night vision and a reflective “eye shine” in a flashlight beam.

Color and dorsal patterning give additional diagnostic cues for PNW specimens. Hobo spiders usually show a series of chevron or V-shaped markings on the abdomen, often in muted browns and tans, whereas common grass spiders (Agelenopsis and related genera) tend to have longitudinal pale stripes down the carapace and abdomen and more pronounced leg banding. Wolf spiders are generally more robust and heavily setose (hairy), with mottled browns, greys, or black patterns that break up into irregular blotches rather than neat chevrons or stripes. Under consistent indoor lighting in Seattle basements or crawlspaces, hobos’ chevrons can appear as a repeating light-and-dark pattern along the abdomen length, while grass spiders’ longitudinal striping runs head-to-tail and is paired with a characteristic tapered abdomen shape.

Behavioral and web-building differences are often the most practical field marks during encounters around Seattle homes. Hobo and grass spiders are funnel-web builders: you’ll find a horizontal sheet of silk leading into a tubular retreat in crevices, foundation gaps, or low vegetation; the retreat is typically tucked against a wall or under debris. In contrast, wolf spiders are cursorial hunters that do not construct capture webs — they actively roam leaf litter, lawns, and basement floors, especially at night. Seasonality matters in identification: male hobos disperse and wander indoors in late summer through autumn (July–October in Puget Sound climate), which explains many indoor sightings; grass spiders remain largely outdoors in lawns and garden edges through the growing season, and wolf spiders show peak activity in spring and early summer when larger immatures and adults are most active.

For homeowners or naturalists trying to confirm an identification without specialist equipment, combine size, web presence, spinneret length, and eye/reflection cues rather than relying on a single trait. A slender, pale-brown spider sitting in a clear funnel retreat with long posterior spinnerets is far more likely an agelenid (hobo or grass spider) than a wolf spider; a robust, hairy spider with a strong eye shine and no sheet web is almost certainly a wolf spider. Misidentifications are common in the PNW — for example, a 15–25 mm leg-span wolf spider seen running across a basement floor at night is frequently called a “hobo” by residents, which inflates perceived hobo encounter rates and can lead to incorrect assumptions about venom risk.

 

What should you do if you think you were bitten by a hobo spider in Seattle

Immediately clean the bite site with running water and mild soap for at least 30 seconds, then pat dry and cover with a sterile dressing. Apply a cold compress (wrapped ice pack or bag of frozen peas) for 10–15 minutes every hour during the first 3–4 hours to reduce swelling and pain; if the bite is on an arm or leg, keep that limb elevated as much as possible for the first 24 hours. Track pain and visible changes by photographing the wound with a dated timestamp and measuring the largest diameter with a ruler—record baseline size (in millimeters or centimeters) at hour zero and again at 24, 48 and 72 hours.

Expect local symptoms to appear within minutes to a few hours: mild-to-moderate pain, localized redness and sometimes a small central blister. Contemporary clinical reviews and regional medical reports indicate that lesions attributed to hobo spider venom in the Pacific Northwest rarely progress to true dermonecrosis; most uncomplicated bites show no expansion beyond about 1–2 cm and resolve or markedly improve within 24–72 hours. Be aware that cool, damp basement conditions common in Seattle can slow drying of the wound and increase the chance of a secondary bacterial infection, which is a more frequent cause of progressive skin breakdown than spider venom.

Seek medical evaluation promptly if any of these objective criteria occur: the reddened area expands by more than 20 mm (2 cm) in diameter over 24–48 hours, a central ulcer or blackened tissue appears within 48–96 hours, red streaking toward the groin or armpit (lymphangitis) develops, fever exceeds 100.4°F (38°C), or pain is escalating despite simple measures. If the bite is on the face, over a joint, or the patient is elderly or immunocompromised, arrange clinician assessment sooner rather than later; clinicians will evaluate for secondary bacterial infection (including community-acquired Staphylococcus aureus), consider wound cultures, and determine whether oral antibiotics or local wound care are indicated.

If you can safely do so, preserve evidence: photograph the spider from multiple angles with a ruler or coin for scale, or confine a live specimen in a clear container (no direct handling) and refrigerate it to keep it intact for potential identification. Accurate identification matters in the Seattle area because wolf spiders (Lycosidae) and grass/funnel weavers (Agelenidae) are common indoors and their bites and behaviors differ; provide your clinician or an entomologist-sized photos and measurements (body length in millimeters) and note the location and timing of the bite (e.g., basement at 2 a.m., sleeping in ground-floor bedroom) to help rule out misattribution.

 

How to prevent hobo spiders from entering homes and basements in the Pacific Northwest

Start with a tight physical-exclusion strategy: seal foundation and sill-plate gaps ≥1/8 inch (≈3 mm) with high-quality exterior caulk or low-expansion spray foam, and install door sweeps that leave less than a 1/8‑inch clearance under exterior doors. Cover foundation vents and dryer/combustion vents with 1/8‑inch (≈3 mm) stainless‑steel mesh rather than the coarser 1/4‑inch hardware cloth if the goal is to exclude small spiders as well as insects. Ensure window and egress well screens are intact (standard 18×16 window screens have ~1.4 mm openings and will block most spiders); replace any screens with holes larger than 2 mm.

Control moisture and the resulting insect prey that attracts hobo spiders: aim for a basement relative humidity of 45–50% year‑round using a dehumidifier sized to the space (e.g., 30–50 pints/day units for 1,000–2,000 ft² basements common in Seattle homes). Grade soil to slope away from foundations at roughly a 5% grade (about 6 inches drop over the first 10 feet) and extend downspouts at least 6 feet (≈1.8 m) from the house to prevent seasonal saturation; Seattle’s October–April rains typically raise basement RH above 65% without these measures, which increases both insects and spider sheltering.

Modify immediate exterior habitat to reduce harborage within the typical 1–20 meter range that hobo spiders exploit: store firewood and lumber at least 20 feet (≈6 m) from the foundation and keep wood raised about 18 inches (≈45 cm) off the ground on racks to reduce suitable crawlspace habitat. Keep vegetation and mulch trimmed back 6–12 inches from foundation walls and replace thick organic mulch within that band with angular gravel or a permeable hardscape where possible; standard landscape plantings and wet mulch next to foundations in Seattle create cool, humid microclimates preferred by funnel‑web builders.

Use monitoring and targeted non‑chemical measures to catch intrusions early: place adhesive (sticky) traps along basement baseboards and in corners every 6–8 feet (≈2–2.5 m) and check weekly during late summer–fall (August–October), when male hobo spiders are most likely to wander indoors. Routine vacuuming of webs, egg sacs and corners—at least once monthly during the active season—removes established silk funnels and reduces local populations more reliably than indiscriminate sprays. For homeowners who use residual perimeter products, apply them narrowly to the foundation band (2–3 feet up and 2–3 feet out from the foundation) and follow product label retreatment intervals—typically every 90 days or after major rain events—but recognize that reducing moisture and harborage is generally the most durable prevention in Seattle’s humid climate.

 

Are hobo spider bites dangerous to humans?

No — confirmed necrotic bites from hobo spiders are extremely rare and multiple modern studies do not support the claim that their venom routinely causes progressive tissue necrosis. Most confirmed encounters produce only mild-to-moderate local pain, redness or swelling that typically peaks within 24–48 hours and improves within 24–72 hours.

How can I tell a hobo spider from a wolf spider or a grass spider?

Hobo (Eratigena) and grass (Agelenopsis) spiders are funnel‑web builders with a horizontal sheet leading into a tubular retreat and have long, visible posterior spinnerets; hobos often show chevron markings on the abdomen while grass spiders have longitudinal stripes. Wolf spiders are more robust and hairy, do not build capture webs, have a distinctive large forward-facing eye pair with a reflective eye‑shine, and are active hunters rather than sedentary in a funnel.

Do hobo spiders live in Seattle basements and other Pacific Northwest homes?

Yes — the hobo spider is an established non‑native species in western Washington and Oregon and is commonly found inside basements, crawlspaces, garages and around foundations where drier indoor microhabitats exist. Adult males are most likely to wander indoors in late summer through autumn, while females often remain in sheltered retreats year‑round.

What should I do if I think I was bitten by a hobo spider?

Clean the site with soap and water, apply a cold compress intermittently, cover with a sterile dressing, and photograph and measure the lesion at baseline and again at 24, 48 and 72 hours. Seek medical evaluation promptly if the redness expands by more than ~20 mm (2 cm) over 24–48 hours, a central blackened ulcer appears within 48–96 hours, red streaking or fever develops, or the patient is elderly or immunocompromised.