The common house spider, scientifically known as Parasteatoda tepidariorum, is a small arachnid often found in homes around the world. Typically measuring about 5 to 10 millimeters in body length, these spiders are usually brown or gray with distinctive markings. They build irregular webs in corners, attics, and basements, where they catch insects. These spiders are harmless to humans and play a beneficial role in controlling pest populations. They are nocturnal hunters, primarily feeding on flies, moths, and other small insects. While they may be unsettling to some, common house spiders are an important part of the indoor ecosystem.