The hobo spider, Tegenaria agrestis, is a species introduced to the Pacific Northwest from Europe. For a time, this species was assigned the unfortunate common name of "aggressive house spider", which has now been changed back to its original name. The hobo spider was first identified in the Seattle area in the 1930's. By 1968, the spider could be found in other areas of Washington and in parts of Oregon and Idaho. The hobo spider is of importance because of its ability to cause necrotic spider bites similar to those of the brown recluse spider.
The hobo spider is a member of the funnel-web spider family Agelenidae. Funnel-web spiders are long-legged, swift-running spiders that build funnel or tube-shaped retreats. The hobo spider runs at an average speed of about 0.45 meters (17 inches) per second, with a maximum speed of about 1.1 meters (40 inches) per second. The hobo spider has a brown cephalothorax (the front portion to which the legs are attached) and brown legs, with darker markings on the cephalothorax. The abdomen has a distinctive pattern of yellowish markings on a grayish back ground, although this pattern can be difficult to discern without the aid of a microscope or hand lens. The pattern is generally more discernible in immature specimens. Unlike many other similar-looking spiders, hobo spiders do not have darker bands (like multiple arm bands) on their legs. Spiders with such banding can be assumed not to be hobo spiders.