Common House Spider

The common house spider, Parasteatoda tepidariorum, is a cobweb spider in the family Theridiidae and one of the most widespread spiders associated with human dwellings. Originally described from Europe, it has spread to become essentially cosmopolitan, thriving in homes, barns, and outbuildings on every inhabited continent. Its close relationship to buildings has made it one of the most frequently encountered spiders by people, even if it often goes unnoticed tucked into an upper corner.

This species builds the classic tangled, irregular "cobweb" that gives the family its common name, spun in undisturbed corners where air currents carry flying insects into the sticky threads. Because it readily colonizes structures and reproduces quickly, it is one of the spiders most people picture when they think of a typical indoor spider.

Although sometimes considered a nuisance simply because of the webs it leaves behind, the common house spider captures flies, mosquitoes, and other small insects that share the same indoor spaces.

• Rounded, bulbous abdomen, typically brownish-gray with darker mottled chevron markings
• Long, thin legs relative to body size, banded with subtle darker rings
• Females are noticeably larger than the small, slender males
• Builds a messy, three-dimensional tangle web rather than a neat circular orb
• Lookalikes include other cobweb spiders such as false widows, which are similarly shaped but often darker and more uniformly colored

True to its name, the common house spider is most often found in and around human structures: basements, garages, sheds, window corners, and the undersides of furniture. Outdoors it also occupies similarly sheltered spots such as rock crevices, hollow logs, and dense vegetation. It is found nearly worldwide in temperate and warm climates, having been spread widely through commerce and travel.

This spider builds an irregular, three-dimensional cobweb in a sheltered corner and waits at its center or nearby retreat for insects to become entangled in the sticky threads. Once prey is trapped, the spider quickly wraps it in silk before feeding. Webs are typically rebuilt or repaired continually rather than replaced daily. Common house spiders are shy and generally retreat or remain motionless when disturbed rather than confronting anything larger than their prey. As indoor predators, they feed on flies, mosquitoes, and other small flying insects.

Females produce multiple tan, papery egg sacs over their lifetime, each containing dozens to a few hundred eggs, which are suspended within or near the web. Spiderlings hatch and disperse on silk threads to establish their own webs nearby. They molt several times over a period of a few months to a year as they grow to adulthood. Common house spiders can live for a year or more indoors, with development continuing year-round in heated buildings even as outdoor populations may slow during colder months.