Giant House Spider
Eratigena atrica
Agelenidae (Funnel-web weavers), Order Araneae. Key family characteristics include three pairs of spinnerets with the posterior pair significantly elongated, and a tendency to build sheet webs ending in a funnel-shaped retreat.
Physical Description
A robust, moderately large spider with a distinctively hairy or velvety appearance. The cephalothorax is broad and brownish, while the elongated oval abdomen is typically dark brown to charcoal gray with a subtle mottled or chevron pattern. Females tend to have larger, more rounded abdomens compared to males.
Size Estimate
Body length ranges from 10 to 18 mm for females and 9 to 15 mm for males, with a total leg span reaching up to 45 to 75 mm, making it one of the largest house spiders.
Coloration & Markings
Predominantly dark brown, grayish-brown, or nearly black throughout the body and legs. The sternum often features pale yellowish markings, and the abdomen may display a faint, broken yellowish-brown herringbone pattern along the dorsal surface.
Web Type
Builds a large, flat, non-sticky sheet web (funnel web) that extends into a tubular retreat in a sheltered corner, crack, or crevice, where the spider waits for prey to walk across the sheet.
Eye Arrangement
Eight small, dark eyes of roughly equal size arranged in two slightly curved, nearly parallel horizontal rows across the front of the cephalothorax.
Leg Characteristics
Long, robust, and covered in numerous visible spines and hairs. The legs are generally uniformly dark brown without distinct banding, held spread out widely in a characteristic flattened hunting posture.
Venom & Safety Information
Venom Information
Contains neurotoxic venom used primarily to immobilize insect prey. The venom is generally considered mild and poses no significant medical threat to humans or pets.
Medical Significance
Harmless to humans. While large specimens possess fangs capable of piercing human skin, bites are extremely rare and typically result only in mild localized pain or redness similar to a bee sting.
Safety Recommendations
Avoid handling with bare hands if startled to prevent accidental defensive bites. If found inside, it can be safely relocated outdoors or into a garage using a cup and a piece of paper.
Habitat & Behavior
Habitat & Range
Native to Europe and Central Asia, but widely introduced to North America (particularly the Pacific Northwest) and other temperate regions. Typically found in dark, undisturbed areas such as cellars, basements, garages, hollow walls, and woodpiles.
Behavior & Temperament
Generally shy, fast-moving, and non-aggressive. They prefer to flee rather than fight when disturbed. Mature males become highly active in late summer and autumn as they wander in search of mates.
Diet & Prey
Carnivorous generalist feeding primarily on crawling insects including flies, woodlice, cockroaches, earwigs, and other spiders. Prey is detected through web vibrations and subdued with venom.
Seasonal Activity
Active year-round indoors, but most frequently encountered in late summer and autumn when mature males wander extensively in search of females during the breeding season.
Description
The Giant House Spider is a familiar yet impressive inhabitant of dark corners and cellars. Known for its remarkable speed and sizable leg span, it constructs intricate sheet webs that funnel into safe retreats. While its imposing appearance often startles homeowners, it is a beneficial predator that helps keep household pest populations under control.
Key Features
Large size, uniform dark brown coloration without bright markings, heavily spined hairy legs, elongated posterior spinnerets, and association with flat funnel-shaped sheet webs in dark indoor spaces.
Similar Species
Hobo Spider (Eratigena agrestis), which looks very similar and requires microscopic examination of genitalia for definitive separation, though giant house spiders are generally darker and larger.
Life Cycle
Females construct silk egg sacs in autumn, hiding them near the web retreat. Eggs overwinter and hatch in spring. Spiderlings mature over two to three years, undergoing multiple molts, with an overall lifespan of up to three years.
Ecological Importance
Acts as an effective apex predator of the indoor and basement microhabitat, naturally controlling populations of nuisance and structural insect pests.
Conservation Status
Not evaluated by the IUCN, but populations are secure, widespread, and thriving globally through human-associated habitats.
Interesting Facts
Giant house spiders are among the fastest running spiders, capable of reaching speeds up to 0.5 meters per second. They were historically introduced to the Pacific Northwest of North America via shipping commerce.
Photography Tips
Photograph from a low angle to capture the full leg span and velvety body texture. Use a macro lens with good natural side-lighting or an external diffuser to highlight the subtle abdominal patterns and eye arrangement without startling the spider.
Identified: 2026-10-01T12:08:54.651022