Picture of a mother American house spider, her egg sac, and a couple of recently hatched spiders.

The American house spider is an extremely common spider that is fairly likely to escape notice since it tends to build its tangled web in secluded locations. Its behavior on its web is quiet and efficient, so it generally does not draw attention to itself. There are several species of this genus, Achaearania. Their coloration consists generally in patterns of shades of brown, and they are rather dull in appearance, all of which makes it more easy for them to slip into the background. They are not known to bite people with any high degree of frequency, and their venom is not known to be dangerous to human beings. Their bodies are generally around a quarter of an inch long.

Many species of American house spider share a body shape and size that makes them similar to widow spiders. The widow spiders, however, are glossy black, usually with a red hourglass or other marking (depending on the species), and are quite venomous.

Like many predators, these spiders seem to have no idea that they might become the prey of some other animal. If they are removed from their webs they are rather helpless because they have such poor vision, and their only concern seems to be to leave the uncomfortable place they find themselves in and find their own web or build another one. Should one somehow find such a spider on one's hand, for example, its most likely reaction would be to hurry to the edge of one's palm and drop off the edge, to let itself down to the floor on a safety line of silk. They do not wander around inside one's house except to find a secure place to build a web. Once they have a web they are quite happy to stay there waiting for flies and mosquitoes. Hanging from strands of silk in these cobwebs one may often see one or more roughly spherical sacs made of spiderweb. These sacs contain their eggs.