Dangerous Spiders in Idaho (2026 Update): Black Widow, Hobo Spider, and What Bites Actually Need a Doctor
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Giant House Spider
Eratigena atrica
Updated May 2026 · Boise, ID
Giant house spiders are among the largest spiders in Idaho, with leg spans up to 75mm (3 inches). They're brown with mottled darker markings and build funnel webs. They're often confused with hobo spi...
Quick Facts
Size12-18mm body, 75mm leg span
ColorBrown with darker markings
Lifespan2-3 years
Active SeasonsLate Summer, Fall
Common LocationsBasements, Garages, Bathrooms
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Identification
How to Identify Giant House Spider
Quick Answer
Giant house spiders are among the largest spiders in Idaho, with leg spans up to 75mm (3 inches). They're brown with mottled darker markings and build funnel webs.
Giant house spiders are among the largest spiders in Idaho, with leg spans up to 75mm (3 inches). They're brown with mottled darker markings and build funnel webs. They're often confused with hobo spiders but are larger with banded legs and more distinct markings.
Behavior
Giant House Spider Behavior & Habits
Understanding how giant house spider behave helps prevent infestations
Giant house spiders are fast runners that build funnel webs in dark corners. Males wander in late summer/fall seeking mates, leading to increased indoor sightings. Despite their alarming size, they're shy and prefer to flee rather than bite. They're actually competitors of hobo spiders.
Dangers
Giant House Spider Risks & Dangers
What giant house spider can do to your health and property
Health Risks
Giant house spiders rarely bite, and bites are not medically significant. Reactions are comparable to a minor bee sting. Their large size makes them frightening, but they're not dangerous.
Property Damage
No property damage. Their webs can be unsightly in corners and crevices.
Warning Signs
Signs of Giant House Spider Infestation
Look for these indicators in your home
Large funnel webs in dark corners
Fast-moving large spiders, especially at night
Increased sightings in August-October
Banded legs visible on close inspection
Webs in basements, garages, and bathrooms
Giant House Spider in Boise & the Treasure Valley
We see most giant house spider calls in September and October, when wandering males show up in basements and garages looking for mates. They're especially common in older Boise neighborhoods with full basements (North End, East End, Boise Bench) and in Garden City and Meridian garages with damp corners. The good news: they actually outcompete and prey on hobo spiders, so a few in your basement may be keeping the more dangerous ones out. Our technicians often find them sharing dark corners with cellar spiders along the foothills, where cooler nighttime temps push them inside.
Our Solution
How We Eliminate Giant House Spider
Professional treatment for complete elimination
Giant house spider control involves treating harboring areas with residual products, reducing prey populations, and sealing entry points. Because they help keep hobo spiders in check, we usually focus on keeping them out of living areas rather than wiping them all out.
Prevention
How to Prevent Giant House Spider
Steps you can take to reduce the risk of infestation
1
Seal gaps around doors and windows2
Use door sweeps3
Reduce clutter that provides hiding spots4
Regular cleaning removes webs and eggs5
Sticky traps along baseboardsFAQ
Giant House Spider Questions Answered
Common questions about identification, prevention, and treatment
Is this a hobo spider or giant house spider?
Giant house spiders are larger with distinctly banded legs. Hobo spiders have solid brown legs without bands. Giant house spiders are actually harmless and prey on hobo spiders.
Why am I seeing so many of these in September and October?
That is mating season. Male giant house spiders leave their funnel webs and wander through basements, garages, and bathrooms looking for females. You are not seeing more spiders overall, just the males that are normally hidden. Sightings usually drop off by November.
Should I kill them or leave them alone?
In Boise, leaving a couple in undisturbed basement corners is actually helpful. They prey on hobo spiders, which carry a much worse reputation. If you want them out of living areas, seal gaps around doors and windows, knock down funnel webs, and call us at (208) 297-7947 for a perimeter treatment that keeps both species outside.
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