"The House Spider" (Achaeranea tepidariorum[theridiidae])

The house spider is so cosmopolitan and so widely distributed that no one is certain of its original homeland. It has been spread by ships, rail and other forms of transport, including its own system of ballooning. Valerio (1977) described second instar house spiderlings as "the floating population or dispersion stage." Second instar house spiderlings can resist starvation for 25 days or longer and ballon long distances (Valerio, 1974). The mortality of these spiderlings is greater than 98 percent. Because of their small size, it is difficult for them to capture food.

The established population of house spiders includes newly established spiderlings with webs, more mature instars and adults of both sexes. With every molt, the spiderlings construct larger webs, requiere more food and consequently the number of individuals in the population is reduced, if prey is a limiting factor. The house spider selects web sites at random. If the sites do not yield prey, the webs are abandoned and a new site is chosen and a new web constructed. Air currents play an important role because they direct the movement of the prey and eventually the spiders end up constructing and maintaining webs where food is most available. The dirty webs that concern most homemakers are largely abandoned ones that have failed to yield enough prey. Because most American homes have low humidities, which causes high mortality to spiders, relatively few flying insects enter dwellings, survival of house spiders is often low. Mature house spiders are much more commonly observed under bridges, in barns, greenhouses and warehouses. The house spider is quite effective predator of small insects such as fruit flies, but it also can handle larger prey. Bristowe (1958) fed a house spider another species of spider nearly three times larger, and the small spider enswathed its victim in silk and paralyzed it with a fatal bite. The house spider is also credited with the capture of small snakes and mice. The early spider authority, H.C. McCook, described the capture of a mouse by its tail. The spider bit the mouse's tail, enswathed it with silk, bit the tail again, etc.

Montgomery (1903) described the mating of the house spider in detail. Briefly, the male acts with great caution, for he is much smaller than the female. The female, usually heavy with eggs, signals the male of her desire by vibrating the web and advancing toward the male. The male then eagerly approaches the female and inserts his palps, injecting his sperm. Any sign of aggressiveness by the female causes the male to drop from the web. Multiple mating is common for both sexes. Shortly thereafter, the female lays about 250 eggs in a silken sac which is flask-shaped, about 1/4 to 1/3 inch long, and usually placed near the center of the web. The egg sacs are moved to warmer or cooler sites, as necessary. Under favorable conditions, two or more egg sacs may be present in a web at the same time, and nine sacs may be produced in a season. The eggs hatch after about a week to 10 days. The first instar spiderlings remain in the sac for one molt. The second instar spiderlings then emerge.