Giant House Spider
Eratigena atrica
Agelenidae (Funnel Weavers), Order Araneae
Physical Description
Robust, elongated body with a distinct, oblong abdomen and a robust, brownish-black cephalothorax. The body is covered in fine, velvety hairs, giving it a somewhat matte texture. Females tend to have slightly larger, more rounded abdomens compared to the slender-bodied males.
Size Estimate
Body length ranges from 10 to 18 millimeters for females (slightly smaller for males), with an impressive leg span reaching up to 75 to 100 millimeters.
Coloration & Markings
Predominantly dark brown, charcoal, or nearly black throughout the body and legs. The abdomen features faint, mottled lighter brownish markings or chevrons down the dorsal center, though these can be very dark and obscured in older or wet specimens.
Web Type
Constructs a flat, dense sheet web that terminates in a tubular retreat where the spider hides, commonly referred to as a funnel web, often built in dark, undisturbed corners.
Eye Arrangement
Eight small eyes of roughly equal size arranged in two slightly curved, horizontal rows of four across the front of the carapace.
Leg Characteristics
Long, robust legs covered in fine hairs and visible spines. The legs radiate outward widely, giving the spider a sprawling posture when at rest.
Venom & Safety Information
Venom Information
Possesses mild, non-lethal venom used primarily to subdue insect prey. Envenomation in humans is extremely rare and typically causes only localized, minor irritation similar to a mosquito bite.
Medical Significance
Harmless to humans. While capable of delivering a bite if tightly trapped against the skin, their venom holds no medical significance.
Safety Recommendations
Avoid direct handling with bare hands; if removal is necessary, capture the spider safely using a glass container and a piece of card, then release it outdoors.
Habitat & Behavior
Habitat & Range
Native to Europe and introduced to North America (particularly the Pacific Northwest). Prefers dark, undisturbed areas such as cellars, basements, garages, hollow trees, and behind furniture.
Behavior & Temperament
Fast-moving, nocturnal hunters that rely on vibrations in their sheet webs to detect prey. Generally docile and reluctant to bite, preferring to flee rapidly when disturbed.
Diet & Prey
Feeds primarily on crawling insects including flies, beetles, woodlice, cockroaches, and occasionally other spiders.
Seasonal Activity
Most commonly seen wandering in late summer and autumn during the peak mating season, while remaining hidden in retreats during the colder winter months.
Description
The Giant House Spider is one of the largest common household spiders, known for its incredible running speed and sprawling legs. While its intimidating size and dark coloration often cause alarm among homeowners, it is a largely harmless and beneficial guest that helps keep household pest populations under control.
Key Features
Large overall size, very long sprawling legs, dark brown to black coloration, and the construction of a flat sheet web ending in a tubular retreat.
Similar Species
Hobo Spider (Eratigena agrestis), which looks very similar and requires microscopic examination of genitalia for definitive differentiation, and Wolf Spiders (Lycosidae), which do not build webs.
Life Cycle
Females produce disc-shaped egg sacs in the autumn, guarding them through the winter. Spiderlings emerge in spring and mature over a period of two to three years, living up to several years.
Ecological Importance
Acts as an effective natural pest controller in residential and natural environments by consuming significant quantities of nuisance insects.
Conservation Status
Not evaluated by the IUCN, but populations are abundant, stable, and widely distributed globally due to human introduction.
Interesting Facts
Despite their frightening appearance and incredible speed, male giant house spiders often wander into homes in late summer specifically searching for mates, which is when they are most frequently encountered by humans.
Photography Tips
Use natural lighting or an off-camera diffuser to capture details without blinding the spider, and photograph from a low angle to highlight its robust proportions and leg span.
Identified: 2026-08-16T09:23:16.334688