Common American House Spider
Parasteatoda tepidariorum
Theridiidae (Cobweb Spiders), Order Araneae. Key family characteristics include a rounded abdomen, comb-like serrated setae on the fourth pair of tarsi used for flinging silk over prey, and building irregular tangle webs.
Physical Description
The spider features a bulbous, globose, rounded abdomen that rises high above the small cephalothorax. The body texture is somewhat smooth with fine hairs. A noticeable dorsal pattern is visible on the abdomen, typical of theridiids.
Size Estimate
Body length ranges from approximately 5 to 8 mm for females and slightly smaller for males, with a leg span up to 20 to 25 mm. This specimen appears to be an adult female based on the prominent, rounded abdomen.
Coloration & Markings
Base coloration ranges from yellowish-brown to dark brown or grey. The abdomen features a distinct mottled pattern of darker brown, grey, and white markings, often including a series of angled chevrons or a central scalloped band.
Web Type
Builds an irregular three-dimensional tangle web, commonly known as a cobweb. These webs are constructed in corners, under furniture, in basements, and around exterior overhangs using sticky silk threads designed to intercept walking or flying insects.
Eye Arrangement
Consists of eight small eyes arranged in two rows of four, typical of the Theridiidae family, positioned on the front of the cephalothorax.
Leg Characteristics
Legs are moderately long and slender, featuring visible dark banding or ring patterns. They lack heavy spination but possess specialized comb-like claws on the hind tarsi.
Venom & Safety Information
Venom Information
Contains mild neurotoxic venom used primarily to subdue small invertebrate prey. It is generally not potent enough to affect large mammals or humans significantly.
Medical Significance
Not medically significant. Bites are extremely rare, usually occurring only when the spider is pressed directly against the skin. Symptoms are typically minor, limited to localized pain, redness, or mild swelling that subsides quickly.
Safety Recommendations
No special precautions needed beyond normal caution. If relocation is desired, gently guide the spider into a container using a piece of cardstock and release it outdoors.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution, highly common in North America and worldwide. Frequently found in close association with human habitations, including homes, garages, sheds, barns, and protected outdoor vegetation or rock crevices.
Behavior & Temperament
Docile and non-aggressive. Spiders hang upside down in their web waiting for prey. When disturbed, they typically drop from the web on a silken thread or retreat to a nearby crevice rather than bite.
Diet & Prey
Feeds primarily on household pests and flying insects including flies, mosquitoes, moths, beetles, and other spiders. Prey is immobilized with silk thrown from the hind legs before being envenomated.
Seasonal Activity
Active year-round indoors, though mating and peak population visibility typically occur during the warmer spring and summer months.
Description
The Common American House Spider is a familiar and harmless resident of human dwellings. Recognized by its bulbous abdomen and messy tangle web in quiet corners, it plays a beneficial role by consuming nuisance insects.
Key Features
Rounded, bulbous abdomen, mottled brownish coloration with chevron patterns, and construction of messy tangle webs in corners of buildings.
Similar Species
Steatoda species (False Black Widows) and Latrodectus species (True Widows). False widows have a shinier, darker, often purplish-black body, while true widows display distinct red markings such as an hourglass.
Life Cycle
Females construct brownish, pear-shaped silk egg sacs containing dozens to hundreds of eggs, attaching them near the web. Spiderlings hatch, undergo multiple molts, and may disperse via ballooning. Lifespan for females can reach over a year.
Ecological Importance
Serves as an effective natural pest control agent inside homes and gardens, consuming large quantities of mosquitoes, flies, and other potential vectors of disease.
Conservation Status
Not evaluated by the IUCN, but populations are secure, abundant, and thriving globally in association with human structures.
Interesting Facts
Despite being common indoors, these spiders can change their color slightly over several weeks to better match their background environment for optimal camouflage.
Photography Tips
Use macro lenses with adequate side lighting or a diffuser to highlight the intricate patterns on the rounded abdomen without startling the spider in its web.
Identified: 2026-09-08T20:20:31.869035