Giant House Spider
Eratigena atrica
Agelenidae (Funnel-web weavers), Order Araneae. Key family characteristics include the construction of sheet-like webs ending in a funnel-shaped retreat, and prominent posterior spinnerets.
Physical Description
A large, robust spider with a relatively smooth carapace and a hairy, oval-shaped abdomen. Females are typically larger and more robust than males, which have noticeably longer legs relative to their body size and enlarged pedipalps.
Size Estimate
Body length ranges from 10 to 18 mm for females and 12 to 15 mm for males, with a formidable leg span that can reach up to 75 to 100 mm. This specimen appears to be a mature adult.
Coloration & Markings
Earthy tones of brown, dirty yellow, and grey. The cephalothorax features distinct pale markings, while the abdomen displays a mottled or chevron-like pattern down the dorsal side.
Web Type
Constructs a flat, non-sticky sheet web that extends out from a tight, tubular funnel retreat where the spider waits for prey. Often built in dark, undisturbed corners.
Eye Arrangement
Eight small, dark eyes of roughly equal size arranged in two slightly curved, transverse rows across the front of the cephalothorax.
Leg Characteristics
Long, strong, and covered in fine hairs and visible spines. The legs often show subtle dark banding and are typically held outstretched in a sprawling posture.
Venom & Safety Information
Venom Information
Contains neurotoxic components designed for invertebrate prey. The venom has very low potency relative to humans and is generally considered harmless.
Medical Significance
Not medically significant. Bites are extremely rare, usually occurring only when trapped against human skin. Symptoms are typically mild, consisting of brief localized pain or redness similar to a mosquito bite.
Safety Recommendations
Simply capture and release using a cup and card if relocation is desired. No professional pest control is necessary.
Habitat & Behavior
Habitat & Range
Originally native to northwestern Europe, but introduced globally, particularly in the Pacific Northwest of North America. Commonly found in human dwellings, basements, sheds, garages, and hollow tree bark.
Behavior & Temperament
Timid and fast-moving. They generally flee when disturbed rather than show aggression. They are nocturnal hunters relying on vibrations in their sheet webs to detect prey.
Diet & Prey
Insects including flies, beetles, woodlice, and other spiders. They rush out of their funnel retreat to subdue prey injected with venom.
Seasonal Activity
Most commonly seen in late summer and autumn when mature males actively wander in search of females.
Description
The Giant House Spider is often feared due to its sheer size and rapid movements, yet it is a largely harmless and beneficial household resident. With a sprawling leg span and mottled brown coloration, it commands attention when encountered indoors, typically resting near its signature funnel web in dark corners.
Key Features
Large overall size, elongated brown-and-yellow mottled abdomen, long spiny legs, and association with flat sheet webs ending in a funnel retreat.
Similar Species
Hobo Spider (Eratigena agrestis). Distinguished primarily through microscopic examination of genitalia, though the Giant House Spider is generally darker and larger.
Life Cycle
Females lay eggs inside a silken sac hidden in the retreat during late summer or autumn. Spiderlings hatch and disperse. Adults have a typical lifespan of two to three years, mating in the late summer.
Ecological Importance
Acts as a natural pest control agent within buildings and outbuildings by reducing populations of household insect pests.
Conservation Status
Not evaluated by the IUCN, but populations are abundant, widespread, and secure.
Interesting Facts
Despite their intimidating appearance and speed (capable of reaching bursts of over a foot per second), they are poor climbers on smooth vertical surfaces like glass bathtubs.
Photography Tips
Use a macro lens or smartphone macro setting with adequate lighting. Maintain a safe distance to avoid startling the spider into retreating.
Identified: 2026-10-01T03:22:31.757508