Common American House Spider
Parasteatoda tepidariorum
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
The spider features a bulbous, rounded abdomen that hangs heavier toward the rear, a distinct and smaller cephalothorax, and relatively delicate joints. Females are notably larger and rounder than males, which have smaller abdomens and longer legs.
Size Estimate
Body length ranges from 5 to 8 millimeters for females, with a leg span of approximately 15 to 25 millimeters.
Coloration & Markings
Base color ranges from yellowish-brown to dark brown or grey. The abdomen typically displays mottled patterns, dark chevron marks, or distinct spots.
Web Type
Irregular, three-dimensional tangle web commonly known as a cobweb, constructed in corners of rooms, windows, or sheltered outdoor structures.
Eye Arrangement
Eight small eyes arranged in two slightly curved rows of four, typical of the Theridiidae family.
Leg Characteristics
Long, thin, tapering legs featuring noticeable dark banding, lacking heavy spination but equipped with comb-like setae on the fourth tarsus.
Venom & Safety Information
Venom Information
Contains mild neurotoxic venom primarily adapted to immobilize small insect prey.
Medical Significance
Harmless to humans. Bites are rare, typically only occurring if trapped against the skin, resulting in minor localized irritation.
Safety Recommendations
No special precautions needed. Can be gently relocated outside using a cup and paper if desired.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution; found worldwide associated with human habitations, basements, sheds, and sheltered outdoor vegetation.
Behavior & Temperament
Timid and non-aggressive; hangs upside down in its web, retreating rapidly to a nearby crevice when disturbed.
Diet & Prey
Feeds on various small insects like flies, mosquitoes, ants, and other spiders caught in its sticky tangle web.
Seasonal Activity
Active year-round indoors, with peak mating and web expansion occurring during the warmer spring and summer months.
Description
A familiar and harmless tenant of human structures, the American house spider constructs messy webs in quiet corners to catch nuisance insects, playing a beneficial role in natural pest control.
Key Features
Bulbous, mottled brown abdomen, irregular cobweb construction, and preference for indoor anthropogenic environments.
Similar Species
Steatoda grossa (False Black Widow), which is darker, glossier, and more robustly built.
Life Cycle
Females produce several brownish, pear-shaped silk egg sacs containing hundreds of eggs. Spiderlings disperse via ballooning after hatching.
Ecological Importance
Serves as an effective natural predator of household pests, including mosquitoes and flies.
Conservation Status
Not evaluated by the IUCN, highly abundant and widespread globally.
Interesting Facts
Females can live for several years and often remain in the same web location for their entire adult lives if undisturbed.
Photography Tips
Use macro lenses with side-lighting to highlight the intricate patterns on the abdomen while keeping a safe, non-disturbing distance.
Identified: 2026-09-09T02:15:27.006426