American House Spider
The common house spider (Parasteatoda tepidariorum), referred to internationally as the American house spider, is a spider species of the genus Parasteatoda that is mainly indigenous to the New World, with P. tepidariorum australis (common gray house spider) also encountered in some parts of Myanmar and Pakistan. American house spiders are synanthropic and build their tangled webs in or near human dwellings, often in secluded areas such as between loose walls and behind open doors and attic windows. Their prey mechanism is similar to that of the other cobweb spiders: the spider follows disturbances transmitted along the web to entangle and then paralyze its prey, which usually consists of household insects and other invertebrates (often considered as pests).
American house spiders are generally dull brown in coloration, with patterns of differing shades often giving a vaguely spotted appearance (particularly noticeable on the legs). Their average body size is a quarter-inch (6 mm) long, but they can be an inch (2.5 cm) or more across with legs outspread. Their size and coloration allow the spiders to blend into the background and escape notice.
Like some other species of the family Theridiidae, P. tepidariorum is similar in body shape and size to widow spiders, which have venom that is classified as potentially dangerous.
As these spiders live in constant proximity to human beings, they are not usually aggressive and will even let a human hand approach their web. Like any other spider, however, they are afraid of bigger foes, and, in most cases, will retreat behind an obstacle (such as a dried leaf or prey remains) upon perceiving more than usual disturbance to their web. Further disturbance may lead to the spider dropping down on a thread, then running away from the web. If the distance is not considerable, it will usually return to its web within a couple of days. Otherwise, it will start a new one.
American house spiders possess poor vision and cannot detect any movement more than 3-4 inches away. If cornered, they will feign death as last resort.
American house spiders will bite humans only in self-defense, when grabbed and squeezed. Regular bites are dry and no more painful than a bee sting, but some females can deliver sharp, venomous bites. If venom is administered with the bite, symptoms may include swelling and itching around the area and may trigger antibody allergies in some individuals. Medical attention is not required, but rest is recommended.
The venom of the American house spider is a neurotoxin similar to that of the black widow, but much less potent. It is often extracted and sold as an insecticide for farm use in the United States and Canada. It is also powerful enough to kill the same species of spider on occasion.