Common House Spider

The Common House Spider (Parasteatoda tepidariorum, formerly Achaearanea tepidariorum) is the small brown spider in nearly every cobweb you see indoors. It is one of the most widely-distributed spiders in the world, established in homes across every inhabited continent, and almost certainly the species responsible for most of the unidentified webs in your home right now. This guide explains how to recognise one, how its biology compares to better-known relatives like the Black Widow, and why it is genuinely harmless despite being a member of the same family.

Quick identification: is this a Common House Spider?

• Body length 5-8 mm for females, 4-5 mm for males. Females noticeably more rounded.
• Variable yellowish-brown to dark brown, often with a mottled or chevron pattern on the abdomen. No two individuals look exactly alike.
• Globular (round) abdomen that is much larger than the cephalothorax in adult females. Males have proportionally smaller abdomens.
• Tangled, three-dimensional cobweb in the corner of a ceiling, in a window frame, or behind furniture. The web is messy and irregular, not flat or spiral.
• Hangs upside-down in the web, often with a small brown spherical egg sac suspended nearby.
• Slow-moving when disturbed. Drops on a single silk line and remains still rather than running. Very different from a Hobo or Wolf Spider.

Anatomy

Cephalothorax

The cephalothorax is small, oval and a uniform yellowish-brown to dark brown. Compared with the rounded abdomen behind it, the cephalothorax often looks almost too small for the spider. There are no special markings: no violin, no chevron, just a smooth dome with eight eyes at the front.

Abdomen

The abdomen is the obvious feature. In a mature female, it is round, glossy and considerably larger than the rest of the spider. The base colour ranges from pale yellow-brown through tan, mid-brown, dark brown to almost black. On top of that base colour, the abdomen often shows a complex pattern of darker chevrons, V-shapes, dots, dashes and pale lines. The pattern is highly variable: two Common House Spiders from the same web can look notably different. This variability is the species’ defining feature.

Legs

Legs are slender, mid-brown, with darker bands at the joints (visible on close inspection). Leg pair I (front) and IV (rear) are the longest. The legs are not particularly hairy and the spider does not look “furry” the way a Wolf Spider does.

Eyes

Eight small eyes arranged in two horizontal rows of four, the standard cobweb-spider arrangement. The eyes are tiny and equally sized. Without magnification you will not see them as individual points, just a darker patch at the front of the cephalothorax.

Where Common House Spiders live

The Common House Spider lives almost exclusively in close association with human structures. Original natural range was probably restricted to a smaller area in the Americas, but the species has been carried by human trade to every continent except Antarctica and is now considered cosmopolitan. Indoors you will find them in window frames, ceiling corners, behind furniture, in basements, in garages, in barns, in commercial warehouses, and in greenhouses (the species name “tepidariorum” means “of warm rooms”). Outdoors they build webs in the eaves of buildings, under porch overhangs, in sheds and around outdoor light fixtures, where their prey gathers in large numbers.

The species is climate-tolerant within human structures: the spider thrives at the temperatures and humidities humans find comfortable.

Webs, prey and behaviour

Common House Spiders build messy, three-dimensional tangle webs (cobwebs). The web has no recognisable geometry: it is a loose meshwork of silk lines running between two surfaces, often a corner where a ceiling meets a wall or where a window frame meets a sill. Some lines have sticky droplets along their length to capture flying prey; other lines act as guy-wires.

The spider hangs upside-down at the densest point of the web, usually near the top of the structure. When prey hits a sticky line and struggles, the spider drops on a silk line, bites the prey and wraps it in silk. Common prey includes house flies, mosquitoes, moths, ants, small beetles, and occasionally other spiders.

One distinctive behaviour: when the web is disturbed, the spider does not run away in the manner of a Hobo Spider. Instead it drops vertically on a single silk dragline and either remains motionless on the line, slowly climbs back up to the web, or descends to the floor and walks slowly away. Combined with their small size and willingness to live in close proximity to humans, this slow non-aggressive behaviour is part of why the species is so easily ignored.

Egg sacs and life cycle

Female Common House Spiders produce a series of small, brown, papery, pear-shaped egg sacs roughly 6 mm across. The female suspends each egg sac in the web near her usual resting position and guards it. A single female may produce ten or more egg sacs over her lifetime, with around 100 to 400 eggs each. The presence of multiple brown spheres hanging in a corner cobweb is a strong sign of a Common House Spider rather than any other species. Spiderlings hatch and disperse on the wind by ballooning on silk threads.

Are they dangerous?

The Common House Spider is in the family Theridiidae, the same family as the Black Widow. Despite that relationship, the Common House Spider is not medically significant. Bites on humans are very rare. When they do occur the effects are mild and transient: a small red mark at the bite site, sometimes a brief sharp pain, occasionally a small itch. Symptoms typically resolve within a day with no treatment. There are no documented cases of serious medical consequences from a Common House Spider bite.

The species’ venom is real and active against insect prey, but the toxins involved are not the alpha-latrotoxin family that gives the Black Widow its medical reputation. In practical terms a Common House Spider is harmless.

Common House Spider vs lookalikes

• Black Widow: glossy black with red hourglass underneath. Larger and more uniformly black. Outdoors only in most cases. See full guide.
• Cellar Spider: tiny pale body with extremely long, thin legs. Hangs in cobwebs but the spider itself looks completely different. See full guide.
• Hobo Spider: brown, larger body, flat funnel web rather than tangled cobweb. See full guide.
• Yellow Sac Spider: pale tan, fast-moving, runs across walls and ceilings rather than sitting in a web. See full guide.

If you are not sure which species you have, try the spider identifier quiz: five quick questions and you will get a ranked best match.

Frequently asked questions

Related guides

• Hobo Spider identification guide and quiz
• Cellar Spider (Daddy Long-Legs)
• Black Widow Spider
• Spiders in North America

 (2026, April 29). Common House Spider. Animal Corner. Retrieved 2026, October 6, from https://animalcorner.org/animals/common-house-spider/

. "Common House Spider." Animal Corner, 2026, April 29, https://animalcorner.org/animals/common-house-spider/.