Common American House Spider, Cobweb Spider
Parasteatoda tepidariorum (most likely) or Steatoda grossa
Theridiidae (Cobweb Spiders), Order Araneae. Key family characteristics include a rounded abdomen, comb-like setae on the fourth tarsus used for flinging silk over prey, and typically building irregular, sticky tangle webs.
Physical Description
The spider exhibits a bulbous, rounded abdomen that is notably larger than the cephalothorax, typical of many cobweb spiders. The body appears compact, with a smooth texture featuring fine hairs. Females are generally larger and more spherical in shape compared to males.
Size Estimate
The body length appears to be approximately 5 to 8 millimeters, with a leg span of roughly 1.5 to 2.5 centimeters, which is typical for an adult female or sub-adult cobweb spider.
Coloration & Markings
The coloration ranges from yellowish-brown to dark brown or greyish. The abdomen often features mottled patterns, darker chevron markings, or spots, which provide camouflage in dim, indoor environments.
Web Type
Builds an irregular, messy tangle web, commonly known as a cobweb. This web is typically constructed in dark, undisturbed corners, under furniture, or near floor junctions, consisting of a three-dimensional lattice of sticky silk threads.
Eye Arrangement
Consists of eight small eyes arranged in two parallel rows of four across the front of the cephalothorax, typical of the Theridiidae family.
Leg Characteristics
Legs are moderately long and thin, tapering toward the ends. They may display faint, alternating dark and light banding. When resting in the web, the legs are usually drawn in close or extended into the sticky scaffold lines.
Venom & Safety Information
Venom Information
Possesses mild neurotoxic venom used primarily to subdue small invertebrate prey. The venom has very low potency relative to humans and is generally harmless to people.
Medical Significance
Harmless to humans. Bites are extremely rare because of their timid nature. If a bite does occur (usually only when pressed directly against human skin), it typically results in mild, localized pain, slight redness, or swelling that resolves quickly without medical intervention.
Safety Recommendations
No special precautions needed beyond standard home cleanliness. If relocation is desired, gently guide the spider into a cup using a piece of paper and release it outdoors.
Habitat & Behavior
Habitat & Range
Found worldwide in association with human habitations. Prefers dark, protected microhabitats such as basements, crawlspaces, corners of rooms, garage rafters, and underneath furniture.
Behavior & Temperament
Generally shy, non-aggressive, and sedentary. They spend most of their time hanging upside down in their webs. When disturbed, they typically drop to the ground or retreat hastily rather than bite.
Diet & Prey
Feeds primarily on crawling and flying household insects, including ants, flies, mosquitoes, roaches, and other small spiders. Prey is entangled in the sticky web, bitten to inject venom, and wrapped in silk.
Seasonal Activity
Active year-round indoors where climate is controlled, though mating and reproductive activity often peak during the warmer spring and summer months.
Description
The Common House Spider is a familiar yet discreet neighbor found in homes across the globe. Preferring the quiet shadows beneath furniture or within dark corners, this master of the cobweb quietly patrols for unwanted household pests. With its globular abdomen and delicate legs, it poses no threat to humans while providing valuable natural pest control services.
Key Features
Rounded, bulbous abdomen, tangled three-dimensional web structure, preference for indoor structural corners and under-furniture locations, and muted brown or greyish mottled patterns.
Similar Species
Steatoda grossa (False Black Widow), which is darker, shinier, and more purplish-black with subtle pale markings; Latrodectus species (Black Widows), which feature glossy black bodies and distinct red hourglass markings.
Life Cycle
Females produce several brownish, pear-shaped or spherical silk egg sacs containing dozens to hundreds of eggs, often hanging them within the web. Spiderlings hatch, undergo multiple molts, and disperse via ballooning or crawling. Lifespan for females can reach up to a year or more.
Ecological Importance
Acts as an effective biological control agent inside human dwellings, significantly reducing populations of nuisance and disease-vector insects like flies, mosquitoes, and gnats.
Conservation Status
Not evaluated by the IUCN, but highly abundant, secure, and thriving globally in human-modified environments.
Interesting Facts
House spiders can survive for extended periods without food if water is available. They often maintain multiple web sites simultaneously, moving between them to find better hunting grounds.
Photography Tips
Use macro photography settings with gentle, diffused lighting or a ring flash to capture details of the mottled patterns and eye arrangement. Maintain a safe distance without disturbing the delicate web structure.
User Notes
Under chair
Identified: 2026-08-14T10:15:53.281161