American House Spider

The American house spider is a small cobweb-weaving spider in the family Theridiidae, one of the most commonly encountered spiders in and around homes across much of North America and, through human transport, in many other parts of the world. Despite the common name, it is not exclusively found in the Americas, having spread widely alongside human structures.

This spider builds the classic messy, three-dimensional tangle web often called a cobweb, typically constructed in undisturbed corners of ceilings, window frames, garages, sheds, and basements. The irregular structure of the web, combined with sticky gumfoot lines that trail down to the ground, is used to snare crawling and flying insects that blunder into the silk.

As a generalist predator of small household and garden insects, the American house spider plays a useful ecological role in controlling populations of flies, ants, and other small arthropods that wander into its web.

• Females have a rounded, bulbous abdomen, roughly 5–8 mm long, typically brownish-gray with darker mottled or chevron-like markings
• Males are smaller and slimmer than females, with a less rounded abdomen
• Legs are relatively long and thin compared to the body, banded with lighter and darker segments
• Builds an irregular, three-dimensional tangle web (cobweb) rather than a symmetrical orb web
• Often confused with other cobweb spiders, including some Steatoda species (false widows), which tend to have a more uniformly dark, shinier abdomen

This species is found across most of North America and has been introduced to parts of Europe, Asia, and elsewhere through human activity. It thrives in and around human structures, favoring undisturbed corners of garages, basements, sheds, barns, window frames, and eaves, though it can also occur in natural settings such as under rocks or logs. It is active year-round in heated indoor spaces and seasonally outdoors in temperate climates.

American house spiders are sedentary web-builders, remaining near their irregular tangle web and waiting for prey to become ensnared in the sticky gumfoot silk lines that run down from the web to nearby surfaces. When an insect touches these lines, the spider quickly moves in to subdue and wrap it. They feed on a variety of small arthropods, including flies, ants, and other insects that wander into their webs, making them a beneficial natural predator around structures. Like most spiders, they generally avoid contact with people and will retreat rather than confront a disturbance, though a spider may bite in self-defense if directly handled or trapped against skin.

Females produce silken egg sacs, often several over their lifetime, each containing dozens to well over a hundred eggs, which are typically suspended within or near the web for protection. Spiderlings hatch after a few weeks and disperse from the egg sac, sometimes ballooning on silk threads to new locations, and begin building their own small webs. Young spiders grow through a series of molts over several months, gradually developing adult coloration and proportions. Adults can live for roughly one to two years under favorable conditions, with reproduction and activity peaking during warmer months.