Common American House Spider, House Cobweb Spider
Parasteatoda tepidariorum
Theridiidae (Cobweb Spiders), Order Araneae. Key family characteristics include a comb-like row of setae (the comb) on the tarsus of the fourth leg used for pulling silk from the spinnerets.
Physical Description
Bulbous, globular abdomen that is noticeably higher than it is long, paired with a smaller, rounded cephalothorax. The body appears smooth with sparse fine hairs. Females are significantly larger and more bulbous than males, which have slimmer abdomens and longer legs.
Size Estimate
Body length ranges from 5 to 8 mm for females and 3.8 to 6 mm for males. Leg span is approximately 1.5 to 2.5 cm. This specimen appears to be an adult female.
Coloration & Markings
Variable background color ranging from yellowish-brown to dark brown or grey. The abdomen features mottled patterns of white, dark brown, and black, typically including a series of dark chevron or triangular spots along the dorsal midline and darker bands on the legs.
Web Type
Irregular tangle web, commonly known as a cobweb. Constructed in sheltered, dark corners, window frames, under furniture, or eaves, consisting of a chaotic mesh of sticky silk threads connected to a retreat area.
Eye Arrangement
Eight small eyes arranged in two slightly curved rows of four. The lateral eyes are closely touching or contiguous, while the median eyes are separated, typical of the Theridiidae family.
Leg Characteristics
Long, slender legs with distinct dark brown or reddish-brown banding. The legs lack heavy spination but possess fine hairs and the characteristic comb-like structure on the fourth pair of tarsi for manipulating silk.
Venom & Safety Information
Venom Information
Contains neurotoxic components designed to immobilize small invertebrate prey. The venom is generally considered low in potency regarding humans and is not medically significant.
Medical Significance
Harmless to humans. Bites are extremely rare, usually occurring only if the spider is directly squeezed or trapped against the skin. Symptoms are typically mild, consisting of localized minor pain, redness, or slight swelling that resolves quickly.
Safety Recommendations
No special safety measures are strictly necessary as they are harmless. If unwanted indoors, gently relocate them outside using a cup and a piece of paper rather than using pesticides.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution, found worldwide in association with human habitations. Prefers indoor environments, basements, sheds, garages, and sheltered outdoor corners, thriving in microhabitats with high insect traffic.
Behavior & Temperament
Docile and non-aggressive. They spend most of their time hanging upside down in their webs. When disturbed, they typically retreat quickly into a dark corner, drop from the web on a silken thread, or feign death.
Diet & Prey
Generalist insectivore feeding on crawling and flying household pests including flies, mosquitoes, ants, beetles, moths, and other spiders. Prey is subdued by wrapping it in sticky silk before delivering a venomous bite.
Seasonal Activity
Active year-round indoors where climate is controlled, though reproduction and egg-sac production peak during the warmer spring and summer months.
Description
The Common American House Spider is an inconspicuous yet beneficial neighbor found in homes across the globe. Recognized by its globular, patterned abdomen and untidy cobweb, this master architect quietly regulates indoor insect populations without posing any threat to human inhabitants.
Key Features
Globular, pear-shaped abdomen with mottled brownish-white chevron patterns, long banded legs, and an untidy tangle web constructed in structural corners.
Similar Species
Steatoda species (False Black Widows) which have glossier, more uniformly dark or purple-black bodies and lack the distinct mottled chevron patterns characteristic of Parasteatoda tepidariorum.
Life Cycle
Females construct multiple brownish, pear-shaped papery egg sacs containing up to several hundred eggs each, which are hung within the web. Spiderlings disperse via ballooning after hatching. Lifespan for females can reach over a year.
Ecological Importance
Acts as an effective natural pest control agent inside buildings and human structures, helping to suppress populations of nuisance insects and disease vectors like mosquitoes.
Conservation Status
Not evaluated by the IUCN, but populations are extremely secure, widespread, and abundant globally due to their close association with human environments.
Interesting Facts
Despite being considered a pest due to the messiness of their webs, these spiders are valuable biological control agents. Females can live for over a year and often remain in the exact same web location for their entire adult life if food is abundant.
Photography Tips
Photograph from a top-down or slight lateral angle to capture the dorsal abdominal patterns and body proportions. Use macro lighting or diffuse flash to highlight the fine mottling without casting harsh shadows.
Identified: 2026-08-22T14:25:18.254292