Overview
The Common House Spider (Parasteatoda tepidariorum), also known as the American house spider, is one of the most familiar and ubiquitous arachnids on the planet. Belonging to the cobweb weaver family (Theridiidae), this modest spider has formed an extraordinarily successful synanthropic relationship with human habitation. Spinning intricate, irregular three-dimensional tangle webs in quiet corners of rooms, barns, and garden sheds, it performs vital natural pest control by capturing nuisance insects.
Biology and Physical Characteristics
Parasteatoda tepidariorum is characterized by a bulbous, spherical abdomen that is mottled with varying patches of yellowish-tan, dark brown, and charcoal gray, bordered by subtle pale chevrons. Its carapace is reddish-brown, and its long, slender legs display alternating dark brown and yellow bands. Females are considerably larger than males. Like all theridiids, it features a specialized ‘comb’ of serrated bristles on the tarsus of its fourth pair of legs, used to comb out sticky silk threads to immobilize prey.
Behavior and Ecology
The web of the common house spider appears haphazard and messy, but it is an ingenious structural trap. The spider anchors taut vertical ‘gumfoot’ lines coated in sticky glue droplets to the ground or wall base. When a crawling insect encounters a gumfoot line, the tension breaks, catapulting the prey into the air where it dangles helpless. The spider dashes down, throwing combs of silk over the prey before administering a paralyzing venomous bite. Females produce distinctive teardrop-shaped, papery brown egg sacs containing up to 400 eggs.
Conservation and Human Impact
Assessed as Least Concern globally, Parasteatoda tepidariorum is exceptionally abundant and faces zero extinction threats. While frequently feared by arachnophobic homeowners, this species is completely harmless to humans; its small chelicerae cannot easily penetrate human skin, and its mild venom causes no medical harm. Instead, house spiders are highly beneficial allies, consuming copious pest insects including mosquitoes, houseflies, and clothes moths.
Interesting Factoid
The American house spider’s web is built with spring-loaded ‘gumfoot’ tripwires: when an unsuspecting bug bumps into the bottom strand, the line snaps upward like a bungee cord, yanking the trapped insect into mid-air so it cannot crawl away!
Last updated: October 2026