Common American House Spider
Parasteatoda tepidariorum
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
The spider has a bulbous, globular abdomen that is noticeably higher than it is long, a smaller oval cephalothorax, and relatively long, thin legs. The overall texture is smooth with fine hairs.
Size Estimate
Body length ranges from 5 to 8 mm for females and slightly smaller for males, with a leg span of approximately 2 to 3 cm.
Coloration & Markings
Base coloration ranges from yellowish-brown to dark brown or grey. The abdomen features mottled patterns, often with dark brown or black chevrons, spots, and sometimes a lighter triangular mark near the front.
Web Type
Builds a messy, irregular tangle web (cobweb) in corners of rooms, under furniture, or in sheltered outdoor structures.
Eye Arrangement
Eight small eyes arranged in two rows of four, typical of the Theridiidae family, with lateral eyes touching or closely spaced.
Leg Characteristics
Legs are long and slender, featuring faint dark banding. They lack heavy spination and are used to deftly navigate the tangled threads of the web.
Venom & Safety Information
Venom Information
Contains mild neurotoxic venom used primarily to immobilize insect prey. It is generally ineffective against humans.
Medical Significance
Not medically significant. Bites are extremely rare, usually only occurring if the spider is squeezed directly against the skin, and typically result in only minor localized pain or redness.
Safety Recommendations
No special safety measures required as they are harmless. If relocation is desired, gently guide the spider into a cup using a piece of paper and release it outdoors.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution worldwide; highly commensal with humans, commonly found indoors in homes, basements, sheds, and garages, as well as sheltered outdoor areas.
Behavior & Temperament
Non-aggressive and timid. They hang upside down in their cobwebs, pulling prey up into the tangle when trapped. They retreat or drop to the ground when disturbed.
Diet & Prey
Feeds on a wide variety of household and garden insects, including flies, mosquitoes, ants, beetles, and other spiders, often subduing prey much larger than itself.
Seasonal Activity
Active year-round indoors, with peak reproductive activity and visibility during the warmer spring and summer months.
Description
The Common American House Spider is a familiar and harmless resident of human dwellings worldwide. Recognizable by its rounded abdomen and messy web, it acts as a dedicated pest controller, quietly reducing populations of nuisance insects around the home.
Key Features
Bulbous, dome-like abdomen with chevron patterns, irregular cobweb construction, and a habit of hanging upside down in the web.
Similar Species
Steatoda species (False Widows), which tend to have a glossier, more intensely colored and rounded abdomen, and Latrodectus species (Black Widows), which possess a distinct hourglass marking.
Life Cycle
Females produce several brownish, pear-shaped silk egg sacs containing up to several hundred eggs. Spiderlings disperse via ballooning after hatching. Lifespan can be up to a year or more.
Ecological Importance
Serves as an effective natural pest control agent inside buildings and human-made structures, helping to regulate populations of flies and mosquitoes.
Conservation Status
Not evaluated by the IUCN, but highly abundant, secure, and thriving globally due to its close association with human habitations.
Interesting Facts
Despite their fragile appearance, these spiders can capture and consume large prey like wasps, beetles, and even small vertebrates by trussing them up with sticky silk.
Photography Tips
Photograph from above or the side using macro settings. Good lighting is essential to capture the subtle chevron patterns on the abdomen against a plain background.
Identified: 2026-09-28T17:11:22.812237