Common American House Spider
Parasteatoda tepidariorum
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
The spider has a bulbous, globular abdomen that is noticeably larger than its cephalothorax, typical of comb-footed spiders. It has relatively slender legs and a smooth exoskeleton without heavy spination.
Size Estimate
Body length ranges from 3 to 8 millimeters, with females being larger than males. The leg span is approximately 15 to 25 millimeters.
Coloration & Markings
Coloration typically ranges from yellowish-brown to dark brown or grayish, featuring mottled patterns, chevrons, or dark spots across the dorsal surface of the abdomen.
Web Type
Builds an irregular, three-dimensional cobweb (tangle web) in corners, under furniture, or near ceilings, equipped with sticky vertical trap threads.
Eye Arrangement
Has eight small eyes arranged in two rows of four, with the lateral eyes touching or closely spaced.
Leg Characteristics
Legs are long and thin, often marked with dark bands or rings, and feature a comb of serrated setae on the fourth tarsus used for flinging silk.
Venom & Safety Information
Venom Information
Possesses mild neurotoxic venom designed to subdue small insect prey; poses little threat to humans.
Medical Significance
Harmless to humans. Bites are rare, typically only occurring if the spider is accidentally trapped against the skin, and result in minor, localized pain or swelling.
Safety Recommendations
No special safety measures required; if relocation is desired, gently guide the spider into a container using a piece of paper and release it outdoors.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution; found worldwide in association with human habitations, including houses, sheds, basements, and barns, as well as sheltered outdoor areas.
Behavior & Temperament
Timid and non-aggressive; hangs upside down in its web and retreats when disturbed or vibrates rapidly to blur its outline.
Diet & Prey
Feeds on a wide variety of household insects, including flies, mosquitoes, ants, beetles, and other small spiders trapped in its web.
Seasonal Activity
Active year-round indoors due to climate-controlled environments, with mating and egg-laying peaking during the warmer spring and summer months.
Description
The Common American House Spider is a familiar and harmless indoor roommate found globally. Preferring dark corners and ceilings, it constructs messy cobwebs where it patiently waits for wandering household pests, acting as a natural form of pest control.
Key Features
Characterized by its bulbous, teardrop-shaped abdomen, irregular cobweb construction, long slender banded legs, and preference for indoor human dwellings.
Similar Species
Can be confused with cellar spiders (Pholcidae), which have much longer, thread-like legs, or black widows (Latrodectus spp.), which are typically shinier black with distinct red hourglass markings.
Life Cycle
Females produce brownish, pear-shaped silk egg sacs containing up to several hundred eggs, guarding them nearby until spiderlings hatch and disperse.
Ecological Importance
Serves as an effective biological control agent inside homes by significantly reducing populations of nuisance and disease-vector insects.
Conservation Status
Not evaluated by the IUCN, but populations are secure, abundant, and thriving globally alongside human settlements.
Interesting Facts
Females can produce up to 17 egg sacs in their lifetime, and spiderlings often engage in ballooning to disperse to new locations.
Photography Tips
Use macro lenses with adequate lighting or flash to capture details of the abdominal patterns and leg banding, maintaining a steady hand since they inhabit tight corners.
User Notes
In a house
Identified: 2026-08-25T09:36:11.541244