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 the cephalothorax. The body is moderately hairy with a rounded shape. Females tend to be significantly larger and rounder than males, which have smaller abdomens and longer legs relative to their body size.
Size Estimate
Body length ranges from 5 to 8 millimeters for females, with a leg span of approximately 1.5 to 2.5 centimeters. This appears to be an adult or sub-adult specimen.
Coloration & Markings
Base coloration ranges from yellowish-brown to dark brown or grayish. The abdomen typically features mottled patterns, dark chevron markings, or spots along the dorsal side, while the legs are distinctly banded with dark rings.
Web Type
Builds an irregular, three-dimensional tangle web commonly known as a cobweb. These webs are constructed in corners of rooms, near ceilings, under furniture, or in sheltered outdoor areas like porches and sheds.
Eye Arrangement
Eight small eyes arranged in two slightly curved horizontal rows of four, typical of the family Theridiidae, with lateral eyes often touching or closely grouped.
Leg Characteristics
Long, slender legs with distinct dark banding. The legs are covered in fine setae and lack heavy spination, ending in small claws used for manipulating silk within the tangle web.
Venom & Safety Information
Venom Information
Contains neurotoxic venom used primarily to subdue small invertebrate prey. The venom has very low potency regarding humans and is not medically significant.
Medical Significance
Harmless to humans. Bites are extremely rare and typically only occur if the spider is squeezed directly against the skin. Symptoms are minor, usually limited to localized redness and mild temporary discomfort similar to a mosquito bite.
Safety Recommendations
No special precautions needed as they are harmless. 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, barns, garages, and basements, as well as sheltered outdoor niches.
Behavior & Temperament
Docile and non-aggressive. They spend most of their time hanging upside down in the center of their cobwebs, reacting to vibrations by retreating or dropping on a silk thread if disturbed.
Diet & Prey
Feeds on various household and garden pests including flies, mosquitoes, ants, beetles, and other spiders. Prey is caught in the tangle web and wrapped in silk before venom is injected.
Seasonal Activity
Active year-round indoors, with peak mating and wandering activity occurring during the warmer spring and autumn months when males search for females.
Description
The Common American House Spider is a familiar and harmless inhabitant of homes worldwide. With its bulbous, patterned abdomen and fondness for quiet corners, it acts as a dedicated pest controller, quietly managing populations of flies and mosquitoes without posing any threat to humans.
Key Features
Globular, bulbous abdomen with mottled brown and cream patterns; distinct dark banding on long, slender legs; tendency to inhabit irregular three-dimensional tangle webs in indoor corners.
Similar Species
Steatoda grossa (False Black Widow) has a darker, shinier, and more purplish-black abdomen without prominent chevrons. Latrodectus species (Black Widows) are shinier black and feature a distinct red hourglass marking.
Life Cycle
Females produce several brownish, pear-shaped silk egg sacs containing hundreds of eggs each, often hanging them within the web. Spiderlings disperse via ballooning after hatching, progressing through multiple molts to reach maturity over a year.
Ecological Importance
Serves a vital role in natural pest control within human dwellings and surrounding gardens, helping to suppress populations of disease-carrying insects and other arthropods.
Conservation Status
Not evaluated by the IUCN, but populations are extremely stable, abundant, and widespread globally due to their close association with human habitats.
Interesting Facts
American House Spiders can change their overall color slightly to match their background environment over a period of time. They are remarkably long-lived for web spiders, with some females surviving for over a year.
Photography Tips
Use macro photography with side lighting to highlight the intricate patterns on the abdomen and the banding on the legs. A tripod helps maintain sharpness since webs often occupy dim corners.
Identified: 2026-09-05T14:35:57.935157