Common American House Spider
Parasteatoda tepidariorum
Theridiidae (Cobweb Spiders), Order Araneae. Key family characteristics include a rounded, bulbous abdomen, comb-like serrated bristles on the tarsus of the fourth pair of legs used for pulling silk from spinnerets, and untidy, three-dimensional tangle webs.
Physical Description
The spider has a distinctive, highly rounded, bulbous abdomen that hangs heavily over a smaller, compact cephalothorax. The legs are relatively thin and spindly with noticeable dark banding. The specimen exhibits the classic silhouette of a mature female cobweb weaver, with a glossy yet textured exoskeleton.
Size Estimate
Body length of approximately 5 to 8 mm for females (excluding legs), with a leg span of roughly 1.5 to 2.5 inches. This specimen appears to be an adult female based on the prominent, rounded abdominal proportions.
Coloration & Markings
Mottled brown, grey, and black coloration with chevron or triangular markings along the dorsal side of the abdomen. The legs feature distinct dark brown or black rings alternating with lighter tan or grey banding.
Web Type
Builds an untidy, three-dimensional tangle web or cobweb in structural corners, eaves, and window frames. The web consists of sticky vertical lines extending downward to anchor points to capture walking or flying prey.
Eye Arrangement
Eight small eyes arranged in two horizontal rows of four, typical of the Theridiidae family, positioned closely together on the anterior portion of the cephalothorax.
Leg Characteristics
Long, slender legs with fine hairs and distinct dark banding. They lack heavy spination but possess specialized comb-like structures on the hind tarsi for manipulating silk.
Venom & Safety Information
Venom Information
Neurotoxic venom specialized for subduing small insect prey. It is mild and generally ineffective against human physiology.
Medical Significance
Harmless to humans. Bites are extremely rare, typically only occurring if the spider is directly squeezed or trapped against the skin. Symptoms are usually limited to mild, temporary local pain or minor swelling.
Safety Recommendations
No special precautions needed. If relocation is desired, gently guide the spider into a cup using a piece of cardstock and release it outdoors.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution worldwide, frequently found in association with human habitations, basements, sheds, and exterior eaves, as well as sheltered natural rock crevices and tree hollows.
Behavior & Temperament
Docile and non-aggressive. They spend most of their time hanging upside down in the center of their web, retreating rapidly into a nearby crevice or dropping to the ground only when heavily disturbed.
Diet & Prey
Inivorous diet consisting primarily of flying or crawling household pests such as flies, mosquitoes, ants, moths, and other small spiders trapped in their tangled webs.
Seasonal Activity
Active year-round indoors, but most noticeable during late summer and autumn when mating season prompts males to wander in search of females.
Description
The Common American House Spider is a familiar yet discreet neighbor found in homes and outbuildings across the globe. Recognized by its bulbous, patterned abdomen and chaotic tangle web tucked into corners, this master pest controller quietly helps regulate indoor insect populations while remaining entirely harmless to humans.
Key Features
Bulbous, highly rounded abdomen; mottled brown and grey pattern with chevrons; untidy cobweb construction; spindly banded legs.
Similar Species
Steatoda grossa (False Black Widow), which is typically darker, shinier, and more purplish-black without the prominent light-and-dark chevron patterning.
Life Cycle
Females construct multiple brownish, pear-shaped paper-like egg sacs containing hundreds of eggs. Spiderlings hatch and disperse via ballooning or crawling short distances. Lifespan for females can extend over a year.
Ecological Importance
Actively functions as a natural biological control agent by consuming large numbers of nuisance and disease-vector insects around human habitations.
Conservation Status
Not evaluated by the IUCN, but highly abundant, secure, and thriving globally alongside human development.
Interesting Facts
These spiders often maintain multiple webs, moving between them to find better hunting locations. They are capable of capturing prey significantly larger than themselves, including small vertebrates on rare occasions.
Photography Tips
Photograph from the side to capture the distinctive abdominal silhouette and leg banding. Use macro lighting or indirect natural light to highlight pattern details without casting harsh shadows.
Identified: 2026-08-31T23:41:55.392933