Common American House Spider
Parasteatoda tepidariorum
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
Rounded, bulbous abdomen with a slightly flattened cephalothorax. The body texture is somewhat smooth with scattered fine hairs, typical of cobweb spiders, featuring a distinctively elevated and globular abdomen.
Size Estimate
Body length ranges from 3 to 8 mm, with a leg span of approximately 15 to 25 mm. This specimen appears to be an adult or sub-adult of average size for the species.
Coloration & Markings
Variable coloration ranging from yellowish-brown to dark brown or grayish. The abdomen features mottled patterns, chevron markings, or dark spots, often with lighter lines bordering the darker patches.
Web Type
Irregular tangle web (cobweb) constructed in dark, undisturbed corners, often near ground level or high up in wall junctions and basements.
Eye Arrangement
Eight eyes arranged in two rows of four, with the lateral eyes touching or closely spaced, typical of the family Theridiidae.
Leg Characteristics
Thin, moderately long legs featuring faint dark banding or rings. They lack prominent spines but have a comb-like row of serrated bristles on the tarsus of the fourth pair of legs used for pulling silk.
Venom & Safety Information
Venom Information
Neurotoxic venom specialized for subduing invertebrate prey. It is low in potency relative to humans and is generally considered not medically significant.
Medical Significance
Harmless to humans. Bites are rare, usually occurring only when the spider is accidentally trapped against the skin. Symptoms are typically mild and localized, akin to a mosquito bite.
Safety Recommendations
No special safety measures are required. If relocation is desired, gently guide the spider into a container using a piece of cardstock and release it outdoors.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution. Highly commensal with humans, frequently found indoors in basements, attics, corners of rooms, and outdoors under rocks, logs, and bark.
Behavior & Temperament
Docile and non-aggressive. They remain stationary in their webs for long periods, dropping to the ground or retreating when disturbed rather than biting.
Diet & Prey
Insects and other small invertebrates including flies, mosquitoes, beetles, and other spiders. Prey is caught in the sticky tangle web and wrapped in silk before envenomation.
Seasonal Activity
Active year-round indoors due to climate control, with peak breeding and wandering activity observed during the warmer spring and autumn months.
Description
The Common American House Spider is a familiar and harmless resident of homes worldwide. Living quietly in dark corners within their messy webs, these unassuming spiders play a beneficial role in controlling household pests while remaining entirely unobtrusive to human occupants.
Key Features
Globular, bulbous abdomen, mottled brown coloration with chevrons, irregular tangle web construction, and preference for indoor corners and dark spaces.
Similar Species
Steatoda grossa (False Black Widow), which is darker, more glossy, and robust; Latrodectus species (Black Widows), which possess shiny black bodies with distinct red hourglass markings.
Life Cycle
Females produce brownish, pear-shaped silk egg sacs containing up to several hundred eggs. Spiderlings disperse via ballooning after hatching. They undergo multiple molts to reach maturity and can live for over a year.
Ecological Importance
Serves as an effective natural pest controller in domestic environments, helping to suppress populations of flies, mosquitoes, and other synanthropic insects.
Conservation Status
Not evaluated by the IUCN, but populations are secure, widespread, and thriving globally in association with human habitats.
Interesting Facts
Females can produce up to 17 egg sacs in a lifetime. They frequently share web space with conspecifics when food is abundant, and they are exceptionally adept at catching pest insects inside buildings.
Photography Tips
Use macro lenses with good side-lighting to highlight the abdominal patterns and eye arrangement. Ensure the background is stable since the spider may be small within the frame.
Identified: 2026-09-20T16:45:43.807481