Are Giant House Spiders Dangerous to People or Pets?
Giant house spiders (Eratigena spp., formerly placed in the genus Tegenaria) are not dangerous to people or pets; bites are uncommon and the venom is generally too mild to cause more than localized pain, redness, or swelling in otherwise healthy individuals. These spiders do not transmit human diseases, and severe systemic reactions are exceptionally rare, though anyone with a known severe allergy to insect or arachnid bites should seek medical advice if bitten.
This question matters to Pacific Northwest homeowners because the region’s cool, wet climate and extensive forested landscapes favor large, fast‑moving spiders that often seek shelter inside buildings during the cooler months. Giant house spiders are among the larger and more conspicuous species encountered in Seattle-area homes, which increases alarm even though they are largely beneficial predators of insects and other spiders. Understanding their seasonal behavior and typical, low medical risk helps homeowners and pet owners respond appropriately when these spiders are found indoors.
Do giant house spiders found in Seattle bite people or pets
Giant house spiders in the Pacific Northwest (Eratigena/Tegenaria species commonly seen around Seattle) are not aggressive toward humans or animals and typically only bite when trapped against skin. Adult body lengths for these spiders are generally 7–18 mm with legspans commonly 40–70 mm (1.5–2.8 in), and their chelicerae (fangs) are small—usually under 2 mm—so penetrating intact adult skin requires significant pressure or pinning. Sightings in Seattle spike in late summer through fall (August–November), when wandering males enter houses to find mates; most encounters are brief and end with the spider escaping or being brushed away rather than biting.
When bites do occur, published clinical descriptions and veterinary reports from temperate regions like the PNW indicate a local reaction rather than systemic toxicity: immediate sharp pain at the site followed by a localized erythema and swelling often measuring 1–3 cm in diameter, sometimes with transient numbness or itching. Symptom duration in documented human cases is typically hours to 48–72 hours, with most signs resolving without progressive tissue damage; there is no reliable evidence that native Eratigena species cause necrotic lesions. Children may show proportionally larger local swelling because of smaller body mass, but severe effects from an isolated bite are uncommon based on regional case series.
Pets such as dogs and cats are bitten infrequently; most veterinary reports from the Pacific Northwest describe minor, focal signs when bites occur—localized swelling 5–20 mm, brief limping if a paw was involved, or increased grooming at the bite site for 12–72 hours. Extremely small animals (neonatal kittens or very small toy-breed puppies) can exhibit more noticeable systemic signs like transient lethargy or anorexia after an envenomation, but such outcomes are rare and not characteristic of the species’ typical venom potency. Large-breed dogs and adult cats generally show only mild local effects, consistent with the modest venom yield and small fang size of these spiders.
Part of the reason bites are rare is behavioral and morphological: Eratigena species are fast, long-legged, and prefer to flee into web retreats in corners or basements rather than confront large mammals, whereas wolf spiders (Lycosidae) are sturdier, ground-dwelling, and sometimes more defensive—wolf spiders’ bodies commonly measure 10–35 mm and their chelicerae are relatively larger, so their bites can produce stronger immediate pain. The hobo spider (Eratigena agrestis), historically blamed for necrotic bites in the PNW, has not been shown in controlled studies to produce consistent necrotic effects; in practice, many suspected “spider bites” around Seattle turn out to be insect bites or secondary skin infections rather than proven arachnid envenomations.
Are bites from Pacific Northwest giant house spiders medically significant for children or pets
Giant house spiders in the Pacific Northwest (the Eratigena/Tegenaria group commonly seen in Seattle-area homes) typically have bodies roughly 6–12 mm long with legspans most often in the 35–75 mm range (about 1.4–3 inches). They are not aggressive toward humans or animals and normally run to escape; bites usually occur only when a spider is trapped against skin (for example, pressed between bedding and a sleeper or grabbed by hand). Documented bite events from these species are rare relative to the number of household encounters, so clinically significant envenomations are uncommon in this region.
When bites do occur in people, the usual clinical picture is limited and localized: an immediate sharp pinch or sting, followed within minutes to a few hours by redness 1–5 cm across, mild swelling typically 5–20 mm, and itching or localized pain. Symptoms most commonly peak within 24–48 hours and then decline over the next 48–96 hours; many reported cases resolve within three days. There is no reliable evidence linking Pacific Northwest giant house spider bites to necrotic wounds; that pattern is associated with other taxa not established in the Seattle area.
Children can show proportionally larger local reactions because of smaller body mass and thinner skin. In documented household reports, a young child’s localized swelling and redness after a small arachnid bite can measure 2–5 cm across and cause several days of discomfort or intermittent itching, whereas an adult with the same bite typically reports a smaller 1–3 cm reaction. Systemic allergic responses (widespread hives, breathing difficulty, collapse) after giant house spider bites are infrequently reported in the medical and veterinary literature from the Pacific Northwest and are much less common than with hymenopteran stings (bees/wasps).
Clinical presentations in pets reflect the same general pattern but with some practical differences: dogs and cats often show immediate behavioral signs (yelp, pawing at the site, excessive licking) and localized swelling that may be more noticeable on the muzzle, paw, or limb. Small dogs under about 5–10 kg may exhibit more pronounced local edema—several centimeters in diameter—and transient lameness for 24–72 hours; systemic signs such as vomiting or collapse following a giant house spider bite are rare in regional veterinary reports. Many suspected “spider bites” in pets ultimately have other causes (insect stings, dermatitis, bacterial infection), so confirmed medically significant envenomations from Pacific Northwest giant house spiders remain an uncommon outcome.
How to identify giant house spiders in the Pacific Northwest versus similar species like wolf or hobo spiders
Giant house spiders in the Pacific Northwest belong to the Eratigena/Tegenaria group (commonly called the giant house spider or Eratigena duellica/atrica complex). Adults typically show an elongated body 7–18 mm long with a legspan most often between 5–9 cm (2–3.5 in) and occasionally approaching 10 cm (4 in) in large females; that long, spindly leg profile is the easiest quick measurement to use indoors. By comparison, hobo spiders (Eratigena agrestis) have a similar body length range (about 6–14 mm) but proportionally shorter legs so the overall legspan is usually under 6 cm (2.4 in), while wolf spiders (family Lycosidae) have a stouter build with body lengths commonly 10–35 mm and legspans that are typically 2–7 cm (0.8–2.8 in) but lack the extremely long, delicate legs of the Eratigena group.
Web structure and where you find the spider indoors are strong field clues. Eratigena/giant house spiders build a horizontal, messy sheet with a characteristic funnel retreat in corners, behind baseboards, or in basement ceiling rafters; those funnels are often 4–20 cm (1.5–8 in) across and persist year-round in the same spot. Hobo spiders also make funnel-shaped webs but tend to place them at ground level on foundations, crawlspaces, or window wells rather than the high corners or attic spaces where giant house spiders frequently set up in Seattle homes. Wolf spiders do not build capture webs at all — they are wandering hunters that enter houses accidentally and will be seen moving actively across floors or walls rather than sitting in a web.
Coloration and anatomical details help when size and web type are ambiguous. Giant house spiders usually show a long abdomen with chevron or mottled brown patterns and faint banding on leg segments; their posterior spinnerets are visibly long compared with many other house species. Hobo spiders are more uniformly brown with a slightly darker V-shaped marking on the cephalothorax and less pronounced leg banding. Wolf spiders are cryptically patterned in tan, gray, or brown with a broader abdomen and a distinctive eye arrangement visible under close inspection: a row of four small eyes on top, two very large eyes in the middle row and two medium forward-facing eyes on the bottom row — that glare from the large eyes can be seen if you shine a light at night.
Practical identification for a Seattle homeowner can be done with simple, specific checks: measure legspan across the extended legs (photo next to a coin or ruler helps), note whether the spider sits inside a funnel web 4–20 cm across in a corner or is actively running across floors, and look for leg proportion (long thin legs vs. stout legs) and abdominal patterning. Seasonal timing gives additional data points: male Eratigena wander inside houses to find mates most often August through October in the Pacific Northwest, so a long-legged, web-associated male seen indoors in September is likely a giant house spider, whereas wolf spiders are most commonly encountered roaming in spring–summer and are typically ground-active rather than web-bound.
Why do giant house spiders appear in Seattle homes in fall and winter and how to prevent infestations
Giant house spiders in the Pacific Northwest are most visible indoors from late August through November when adult males leave their webs to seek mates; peak wandering typically occurs in September and October. Seattle’s temperate autumns — with daytime highs often in the mid-50s to low-60s °F (13–17 °C) through October and mild nights — allow males to remain active longer than in colder inland climates, so homeowners commonly see an uptick of large, 10–20 mm body-length spiders (legs adding several centimeters) during those months. Females remain near their funnel retreats and egg sacs, so an increase in wandering males is the primary reason occupants notice more spiders indoors rather than a sudden growth in local populations.
Shelter-seeking and prey availability drive winter house entry in Seattle’s wet climate. Rainy, windy periods and falling temperatures push spiders toward dry, stable microclimates; basements, attics, wall voids and garage corners that hold 40–60% relative humidity and temperatures above freezing provide refuge. At the same time, exterior lights and indoor clutter concentrate flying and crawling insects (moth and fly activity can remain significant into October), creating an attractive food source. Homes with accessible crawlspaces, open foundation vents or accumulated leaf litter close to the foundation see higher indoor spider presence because these features supply both harborage and an insect food web.
Structural exclusion and simple landscape adjustments significantly reduce autumn incursions. Seal gaps greater than about 3 mm (1/8 inch) around doors, window frames and utility penetrations with silicone caulk or backer rod; install door sweeps and repair torn window screens. For foundation and attic vents, fit hardware cloth in the 3–6 mm (1/8–1/4 inch) mesh range to cut insect entry while still allowing airflow. Move stacked firewood at least 6 meters (20 feet) from the house and elevate it roughly 45 cm (18 inches) off the ground; trim shrubs and groundcover to leave a 30 cm (12 inch) cleared perimeter to reduce the transitional habitat spiders use to access siding and eaves.
Interior housekeeping and targeted maintenance reduce food and harborage that sustain indoor spider populations. Vacuum corners, baseboards and ceiling junctions weekly through October to remove funnel webs and egg sacs (female sacs are typically several millimeters up to about 1 cm across and may contain dozens to a couple hundred eggs) and empty or dispose of the vacuum canister contents outdoors. Lower indoor relative humidity to below about 50% in crawlspaces or basements with a dehumidifier to make those areas less hospitable, and limit porch and exterior lighting or switch to long-wavelength “bug” bulbs to reduce night-flying prey. Regularly decluttering storage areas, sealing cardboard boxes, and repairing gaps where utilities enter will reduce both the spiders’ hiding places and the insects that sustain them.
What are safe ways to remove or deter giant house spiders from Pacific Northwest homes and when to call pest control
For immediate, pet‑safe removal of a large Eratigena/Tegenaria “giant house spider” (adults typically have a legspan of about 1.5–2.5 inches / 4–6 cm in the Pacific Northwest), use a clear jar or 16–32 oz (500–1000 ml) container and a stiff piece of cardboard to trap and relocate the spider outdoors. If you vacuum webs and spiders, use the wand attachment, vacuum thoroughly along baseboards and ceiling corners, and empty the canister or sealed bag into an outdoor trash can within 24 hours—this prevents egg sacs or survivors from re‑establishing inside the machine. Inspect for and remove egg sacs (silky, spherical, ~5–10 mm across) when you vacuum; eggs can take 2–8 weeks to hatch depending on temperature, so increase vacuuming frequency to weekly during fall and early winter when indoor activity peaks.
Physical exclusion and habitat modification are the most reliable deterrents in Seattle’s mild, humid climate. Seal exterior gaps larger than about 3 mm (1/8 inch) with silicone caulk; install door sweeps and weatherstripping on exterior doors and fit window screens of standard 16×14 mesh (about 1.4 mm openings). Keep vegetation and mulch trimmed 6–12 inches away from foundation walls, store firewood at least 20 feet from the house and elevated 12–18 inches off the ground, and reduce outdoor light that attracts prey insects (use yellow “bug” bulbs or shield fixtures). In damp basements common in the Puget Sound region, run a dehumidifier to maintain relative humidity near 40–50%—that level discourages many prey insects and reduces the appeal of basements and crawlspaces to spiders.
When you prefer non‑chemical controls, place glue/sticky traps (glue boards ~6×6 cm or similar) along baseboards and behind furniture at roughly one trap every 6–8 feet; replace traps every 2–4 weeks or when covered with dust or insects. Food‑grade diatomaceous earth can be applied as a light dust into dry cracks and voids, but its efficacy drops sharply above about 60% relative humidity—so in rainy Seattle or damp basements it will often be less effective than in dry inland homes. For chemical options, licensed applicators commonly use low‑odour residual treatments (pyrethroid‑based liquids) applied as a 2–3 foot (0.6–0.9 m) exterior perimeter band and targeted indoor crack‑and‑crevice treatments; these products can provide 60–90 days of control but require adherence to label directions and pet/child safety precautions. Note: some pyrethroid formulations and permethrin products are toxic to cats, so professional application minimizes risk.
Call a licensed pest‑management professional when you see sustained activity despite nonchemical steps, when there are multiple egg sacs or female webs indoors, or when sightings exceed a few adults per week over a 3–4 week period. Also engage professionals if you cannot access attics/crawlspaces, if residents are very young, elderly, pregnant, immunocompromised, or have concerns about pesticide use around pets—technicians can provide targeted inspections (often within 1–2 weeks), document entry points, and implement interior crack‑and‑crevice or exterior perimeter programs with re‑treatments commonly scheduled every 60–90 days depending on the product and season. If indoor sightings persist after 4–6 weeks of sealing, vacuuming, and trap placement, a focused professional inspection will identify whether the population is breeding inside or simply a seasonal influx of wandering males.
Are giant house spiders dangerous to people or pets?
No — Pacific Northwest giant house spiders (Eratigena/Tegenaria) are not considered dangerous to people or pets; bites are uncommon and their venom typically causes only localized pain, redness, or swelling. They do not transmit diseases, and severe systemic reactions are rare, though anyone with a known severe allergy should seek medical advice if bitten.
Can a giant house spider kill my dog or cat?
It is extremely unlikely — veterinary reports from the PNW show bites to dogs and cats usually cause only mild, focal swelling, brief lameness, or increased grooming for 12–72 hours. Very small or neonatal animals may show more noticeable transient signs after a bite, so contact your veterinarian if a pet develops vomiting, collapse, or progressive symptoms.
How do I tell a giant house spider from a wolf spider or hobo spider?
Giant house spiders (Eratigena) have very long, spindly legs and sit in a horizontal funnel web in corners or rafters, with legspans commonly 4–9 cm; hobo spiders have proportionally shorter legs and place funnel webs near the ground, while wolf spiders are stouter, do not build capture webs, and are active hunters with a distinctive large-eyed arrangement. Measuring legspan, noting web type and placement, and observing leg proportions are the most practical ID clues for Seattle homeowners.
How can I prevent giant house spiders from entering my Seattle home?
Use physical exclusion and habitat modification: seal gaps larger than about 3 mm with silicone caulk, install door sweeps and intact screens, fit 3–6 mm hardware cloth over vents, and move stacked firewood at least 6 m (20 ft) from the house and elevate it ~45 cm (18 in). Also reduce attractants by trimming vegetation 30 cm (12 in) from foundations, lowering basement humidity to ~40–50%, reducing exterior lighting or switching to “bug” bulbs, and vacuuming funnel webs and corners weekly during the late-summer/fall peak.