Common American House Spider
Parasteatoda tepidariorum
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
Rounded, bulbous abdomen with a slightly smaller cephalothorax. Females tend to be larger with a significantly more spherical abdomen, while males are smaller and narrower.
Size Estimate
Body length ranges from 5 to 8 mm for females and 3.8 to 5 mm for males, with a leg span of roughly 1.5 to 2.5 cm.
Coloration & Markings
Dull brownish-yellow to dark brown base coloration, featuring chevron or patterned markings along the dorsal side of the abdomen that can vary from light grey to nearly black.
Web Type
Irregular tangled cobweb constructed in corners, window frames, and protected structural angles.
Eye Arrangement
Eight eyes arranged in two rows of four, typical of the Theridiidae family, with lateral eyes often touching.
Leg Characteristics
Long, slender legs with faint dark bands or rings, lacking heavy spination but featuring a comb-like serrated row of bristles on the fourth tarsus.
Venom & Safety Information
Venom Information
Neurotoxic venom primarily targeted at small invertebrate prey; generally weak and ineffective against human physiology.
Medical Significance
Not medically significant. Bites are rare, mostly defensive if pressed against skin, resulting in minor localized pain or swelling comparable to a mild insect sting.
Safety Recommendations
Keep living areas clean to deter prey, gently relocate spiders outside using a cup and paper if desired, and treat any accidental minor bite with basic antiseptic.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution worldwide; frequently found indoors in human dwellings, garages, basements, and outdoors under rocks, woodpiles, and bark.
Behavior & Temperament
Timid and non-aggressive; typically retreats or drops from the web when disturbed.
Diet & Prey
Generalist predator feeding on crawling and flying insects such as flies, mosquitoes, beetles, and other spiders.
Seasonal Activity
Active year-round indoors, with peak outdoor visibility and reproductive activity during the warmer spring and summer months.
Description
The Common American House Spider is a familiar and harmless indoor resident, often found hanging upside down in its messy cobweb near windows or in dark corners. It plays a beneficial role in controlling household insect pests.
Key Features
Bulbous, rounded abdomen, brownish coloration with chevron patterns, and preference for building messy, three-dimensional cobwebs in structural corners.
Similar Species
Steatoda species (False Black Widows) and Latrodectus species (True Black Widows), which are distinguished by darker, glossier bodies and distinctive red hourglass markings.
Life Cycle
Females produce several brownish, pear-shaped silk egg sacs containing up to several hundred eggs; spiderlings hatch and disperse via ballooning.
Ecological Importance
Serves as an effective natural pest controller in homes and gardens, consuming large numbers of nuisance and disease-carrying insects.
Conservation Status
Not evaluated by the IUCN, highly abundant, and globally secure with stable populations.
Interesting Facts
Females can live for several years, frequently hanging around the same web site if undisturbed, and they actively tend to their egg sacs until hatching.
Photography Tips
Use macro lenses with adequate lighting or a ring flash, approach slowly to avoid triggering their escape response, and capture both dorsal and lateral views for clear identification.
Identified: 2026-09-22T23:09:21.398441