According to Pete Haws, author of "Getting to Know Spiders," there are approximately 3,000 species of spiders in North America, but only a few of them live indoors, and even fewer still are actually poisonous to humans. Those spiders that are poisonous and live in the home can be quite dangerous to humans if disturbed. However, many of these spiders prefer to live inconspicuously in areas of the home that are seldom disturbed by humans.
Brown Recluse Spiders
The brown recluse spider earned its name because of its shy, reserved nature. Brown recluses are commonly found in homes in the southern and midwestern states, but are rarely seen by humans because they generally hide in dark, dry areas of the home and are only active at night. The bites from the brown recluse, which are not often felt initially, are only life-threatening to humans with weakened immune systems. However, bites can be extremely painful. If you are bitten, seek immediate medical treatment.
Black Widow Spiders
The black widow spider is so named because the female of the species will generally kill and eat her male partner after mating. The female black widow can be identified by her shiny black color and the characteristic red hourglass shape on her abdomen. The bite from a female black widow can be fatal to small children and people who already have medical conditions or health concerns. The bite is sometimes painless at first, but will become painful within a few hours. The male black widow spider is also black, but not quite as shiny, and significantly smaller than the female. The male also does not carry the potentially deadly venom. If they are living in your home, you will most likely find them in dark corners of the ceiling, closets, and other quiet and undisturbed areas. Black widow spiders live throughout the United States.
Hobo spiders hang out in the northwestern United States--Idaho, Washington, Montana, Wyoming, Oregon, Utah and some areas of Colorado. Hobo spiders prefer ground level moist areas of the home such as basements. The male and female hobo spiders are about the same size, but the male’s mouth parts, called palpi, are larger, and according to the National Park Service, resemble boxing gloves. The hobo spider is in the family of funnel-web spiders that produce a funnel-shaped web to catch their prey. Hobo spiders can be aggressive with little to no provocation, and can inflict a serious and painful bite. Although never fatal, bites from the Hobo spider can cause headaches, nausea, vomiting, blurred vision and pain and swelling in the bite area.