Common American House Spider
Parasteatoda tepidariorum
Theridiidae (Cobweb Spiders), Order Araneae. Key family characteristics include a rounded abdomen, comb-like serrated bristles on the tarsus of the fourth leg used to pull silk, and building irregular tangle webs.
Physical Description
The spider has a bulbous, swollen, high-domed abdomen that is notably larger than the cephalothorax. The body features a somewhat glossy texture with fine hairs. The proportions show short-to-medium slender legs relative to the heavy, rounded body.
Size Estimate
Body length ranges from 5 to 8 millimeters for females, with a leg span of roughly 1.5 to 2.5 centimeters. This specimen appears to be an adult female based on the notably large, rounded abdomen.
Coloration & Markings
Base coloration varies from yellowish-brown to dark grayish-brown. The abdomen features a complex pattern of dark chevrons, spots, and sometimes whitish or pale mottling. The legs show distinct dark banding at the joints.
Web Type
Constructs an irregular, three-dimensional tangle web commonly known as a cobweb. The web is anchored in corners, under structures, or inside sheltered cavities like machinery and eaves, consisting of sticky tension lines extending in various directions.
Eye Arrangement
Consists of eight small eyes arranged in two slightly recurved rows of four, typical of the Theridiidae family, with lateral eyes situated close together or touching.
Leg Characteristics
Legs are moderately slender with distinct dark brown or blackish banding. The fourth pair of legs possesses a specialized comb of serrated setae used for wrapping prey. Legs are typically held close to the body or spread out within the tangle web.
Venom & Safety Information
Venom Information
Neurotoxic venom typical of cobweb spiders, but specialized for invertebrate prey. It has low potency relative to humans and is generally not considered medically significant.
Medical Significance
Harmless to humans. Bites are rare and usually only occur if the spider is squeezed directly against the skin. Symptoms are typically limited to minor, localized pain, redness, or mild swelling that resolves quickly without treatment.
Safety Recommendations
No special control measures are necessary as they are harmless and beneficial. If relocation is desired, gently guide the spider into a container using a piece of card or paper and release it outdoors.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution found worldwide in association with human habitations, outbuildings, basements, sheds, and sheltered outdoor niches such as under vehicles or equipment.
Behavior & Temperament
Docile and non-aggressive. They spend most of their time hanging upside down in the center of their cobwebs. When disturbed, they typically drop from the web on a silken thread or retreat into a nearby crevice.
Diet & Prey
Feeds opportunistically on a wide variety of crawling and flying insects trapped in the cobweb, including flies, mosquitoes, beetles, ants, and occasional other spiders.
Seasonal Activity
Active year-round indoors, with peak outdoor visibility and reproductive activity during the warmer spring, summer, and autumn months.
Description
The Common American House Spider is a familiar yet unobtrusive neighbor, frequently found spinning its messy scaffolding of silk in dark corners, sheds, and vehicle engine bays. With its high-domed, patterned abdomen and preference for quiet, undisturbed shelters, this master architect of the cobweb plays a quiet role in keeping pest insect populations in check around human environments.
Key Features
Bulbous, globular abdomen with dark chevron patterns, irregular three-dimensional tangle web construction, and typical habitation within human-made structures.
Similar Species
Can be confused with Steatoda species (False Black Widows), which tend to have glossier, more solid-colored or differently patterned abdomens, or Latrodectus species (Black Widows), which are jet black with distinct red hourglass markings beneath.
Life Cycle
Females construct brownish, pear-shaped papery egg sacs containing up to several hundred eggs, hanging them within the web. Spiderlings hatch, disperse locally via ballooning or crawling, and undergo multiple molts to reach maturity over several months.
Ecological Importance
Serves as an effective natural pest controller in and around human dwellings, preying heavily on household insect pests like mosquitoes, flies, and gnats.
Conservation Status
Not evaluated by the IUCN, but populations are secure, abundant, and widely distributed globally due to close association with human habitats.
Interesting Facts
These spiders are remarkably adaptable to indoor environments where central heating allows them to remain active and reproduce year-round, well protected from winter elements.
Photography Tips
Use a macro lens to capture the fine abdominal patterns and eye arrangement. Ensure good lighting or an external flash to bring out details in darker areas, and shoot from a stable position since the spider hangs suspended in a loose web.
Identified: 2026-09-14T15:55:07.072688