Giant House Spider
Eratigena atrica
Agelenidae (Funnel-web weavers), Order Araneae. Characterized by long spinnerets and building sheet webs with a retreat tube.
Physical Description
Robust, elongated body with a distinct oval abdomen and a somewhat flattened cephalothorax. Covered in fine, velvety hairs rather than being heavily spiny. Features prominent palps and a muscular stance.
Size Estimate
Body length ranges from 10 to 18 mm for females (sometimes slightly smaller for males), with a leg span reaching up to 45 to 75 mm, making it one of the larger common household spiders.
Coloration & Markings
Dull brown to dark brown or charcoal coloration. The cephalothorax typically features indistinct yellowish markings or spots, while the abdomen shows a subtle, broken herringbone or mottled pattern.
Web Type
Builds a large, flat, non-sticky sheet web (funnel web) that extends into a tubular retreat where the spider waits for prey.
Eye Arrangement
Eight small eyes arranged in two slightly curved, nearly parallel horizontal rows of four, set closely together on a prominent tubercle at the front of the cephalothorax.
Leg Characteristics
Long, robust, and tapering legs covered in fine hairs and prominent spines, well-adapted for rapid sprinting across surfaces rather than leaping.
Venom & Safety Information
Venom Information
Neurotoxic venom used to immobilize insect prey. It is relatively weak and generally ineffective against human physiology.
Medical Significance
Harmless to humans. A bite is extremely rare and usually only occurs if the spider is squeezed or trapped against bare skin; symptoms are typically minor, akin to a mild bee sting, and resolve quickly.
Safety Recommendations
To avoid encounters, seal cracks in foundations and shake out stored shoes or clothing. If found indoors, they can easily be safely relocated outside using a container and a piece of stiff paper.
Habitat & Behavior
Habitat & Range
Native to Europe and introduced to parts of North America (particularly the Pacific Northwest). Commonly found in dark, undisturbed corners of houses, cellars, sheds, and garages, as well as woodpiles and hollows outdoors.
Behavior & Temperament
Fast-moving, nocturnal hunters that rely on vibrations in their sheet web to detect prey. Generally timid and docile, preferring to flee rather than bite when disturbed.
Diet & Prey
Feeds primarily on household insects such as flies, cockroaches, silverfish, and other smaller spiders.
Seasonal Activity
Most commonly seen wandering in late summer and autumn (August through October) during the peak breeding season.
Description
The Giant House Spider is a familiar yet impressive arachnid often encountered indoors during late summer and autumn when males wander in search of mates. Known for its remarkable speed and sizable leg span, it plays a beneficial role by keeping household insect populations in check.
Key Features
Large overall size, long hairy legs, dark brown coloration with subtle abdominal markings, and the characteristic funnel-shaped retreat connected to a flat web.
Similar Species
Hobo Spider (Eratigena agrestis) and other related funnel-web species; distinguishing often requires microscopic examination of genital structures.
Life Cycle
Females construct silk egg sacs in hidden areas during autumn, laying dozens to hundreds of eggs. Spiderlings hatch and disperse, undergoing multiple molts to reach maturity over a 2 to 3 year lifespan.
Ecological Importance
Acts as an effective natural pest controller in residential and natural environments, regulating insect populations and serving as food for larger predators.
Conservation Status
Not evaluated by the IUCN, but highly abundant and widespread globally due to human introduction and commensal living.
Interesting Facts
Despite their intimidating size and incredible speed—once holding records for running velocity among spiders—they are completely harmless to humans and avoid contact whenever possible.
Photography Tips
Photograph from above or the side using macro settings with natural or diffused lighting. Keep a safe distance to avoid startling the spider into fleeing.
Identified: 2026-08-16T09:11:17.169148