Common American House Spider, Theridiid House Spider
Parasteatoda tepidariorum
Family Theridiidae (Cobweb Spiders), Order Araneae. Key family characteristics include a globular abdomen, small eyes, and a comb of serrated bristles on the tarsus of the fourth pair of legs used for pulling silk.
Physical Description
The spider has a bulbous, rounded abdomen that sits relatively high, a smaller oval cephalothorax, and relatively long, thin legs. The body surface is finely haired, and females are notably larger and rounder than males.
Size Estimate
Body length ranges from 5 to 8 mm for females and 3.8 to 4.7 mm for males, with a leg span of roughly 2 to 3 cm. This specimen appears to be an adult or subadult.
Coloration & Markings
Base coloration ranges from yellowish-brown to dark brown or grey. The abdomen typically features mottled patterns, chevron markings, or dark spots, while the legs are visibly banded with darker rings.
Web Type
Builds an irregular, three-dimensional tangle web, commonly known as a cobweb, typically constructed in corners of rooms, near ceilings, under furniture, or around porches and exterior structures.
Eye Arrangement
Consists of eight small eyes arranged in two slightly curved horizontal rows of four, typical of the Theridiidae family, with median eyes sometimes situated on slight tubercles.
Leg Characteristics
Legs are long, slender, tapering, and distinctly banded with darker brown or grey rings. They possess fine hairs and a comb of serrated bristles on the hind tarsi for handling sticky silk.
Venom & Safety Information
Venom Information
Possesses mild neurotoxic venom used primarily to immobilize small insect prey. It is not considered dangerous to humans or large pets.
Medical Significance
Harmless to humans. Bites are rare, typically only occurring if the spider is trapped directly against the skin. Symptoms are generally limited to minor localized pain, redness, or swelling, similar to a mild mosquito bite.
Safety Recommendations
No emergency action needed. If desired, gently coax the spider into a cup using a piece of paper and release it outdoors. Keep living areas clean to discourage web building.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution found worldwide in temperate and tropical regions. Prefers human-made structures, homes, outbuildings, basements, and occasionally sheltered outdoor locations like rock overhangs and tree bark.
Behavior & Temperament
Timid and non-aggressive. Spiders hang upside down in their webs waiting for prey. When disturbed, they typically drop from the web on a silk thread or scurry to a nearby crevice.
Diet & Prey
Feeds primarily on household insects including flies, mosquitoes, ants, beetles, moths, and other spiders. Prey is captured in the sticky web threads, wrapped securely in silk, and envenomated.
Seasonal Activity
Active year-round indoors in climate-controlled environments, with mating and egg-laying activity peaking during the warmer spring and summer months.
Description
The Common American House Spider is a familiar yet harmless indoor roommate. With its globular abdomen and haphazard web built in quiet corners, this spider plays a beneficial role by keeping unwanted household pests in check without posing any danger to humans.
Key Features
Globular, patterned abdomen, irregular tangle web, banded legs, and a preference for human dwellings and undisturbed indoor corners.
Similar Species
Can be confused with the Brown Recluse (Loxosceles reclusa), which lacks banded legs, has a distinctive violin pattern on the cephalothorax, and builds sheet webs instead of tangle webs.
Life Cycle
Females produce several brownish, pear-shaped silk egg sacs containing up to several hundred eggs. Spiderlings hatch after a couple of weeks, undergo multiple molts, and disperse via ballooning or crawling. Lifespan can exceed a year for females.
Ecological Importance
Serves as an effective natural pest control agent inside homes and buildings, helping to suppress populations of nuisance insects like flies and mosquitoes.
Conservation Status
Not evaluated by the IUCN, but populations are abundant, widespread, and thriving globally alongside human habitation.
Interesting Facts
House spiders can change their overall color slightly to match their background environment over a series of molts, and females will fiercely guard their egg sacs against intruders.
Photography Tips
Use macro lenses with good side lighting to highlight the leg banding and abdominal patterns. Photograph from a slightly elevated angle while the spider rests in its web.
Identified: 2026-09-07T09:29:22.185645