According to etymologists at the University of Wyoming, more than 3,000 species of spiders are found in the United States. The most venomous among these, the black widow, is considered of serious health importance in Wyoming. The venom of the Western black widow contains a neurotoxin that destroys nerve tissue. Deaths are rare, but the bites are extremely painful and may cause difficult breathing, especially in allergic victims. Brown recluse spiders don't live in most parts of Wyoming; however, some have been sighted in extreme southeastern sections of the state. Hobo spiders resemble brown recluse spiders and sometimes are mistaken for them. The hobo spider is also called the aggressive house spider. The bite of a hobo spider is painful, but the venom is not as powerful as that of the black widow or brown recluse.
Hobo spiders are marked with a herringbone or multiple chevron pattern on top of the abdomen. This fast-running brown-colored spider is about 1 to 1 3/4 inches long, including the legs. Because of its brown color, it is sometimes mistaken for the more dangerous brown recluse. However, the brown recluse is only about three-eighths of an inch long and has a distinct violin pattern on the top side of the head that distinguishes it from the hobo. The red or red-orange "hourglass" on the underside of the abdomen of black widows distinguishes them. The Western widow often has two unconnected spots that appear as a rectangle instead of the typical hourglass shape.
Hobo and Western widow spiders are prevalent in the Western states of Wyoming, Montana, Utah, Colorado, Oregon, Idaho and Washington. Hobo spiders prefer moist areas such as basements, window wells and woodpiles. They frequently nest indoors between boxes or storage items, behind furniture and in closets. Western widow spiders seek out piles of wood, leaves and other areas with large amounts of debris. They build webs between objects and trap their victims in the sticky web.
Use caution when encountering any spider, since it is difficult to identify one that poses a risk of danger from one that does not. Take special care when working outdoors in the garden or cleaning closets or storage areas. It is important to educate yourself about dangerous spiders and find out how to prevent exposure to humans and domestic animals.