The hobo spider, Tegenaria agrestis (Walckenaer 1802), was accidentally introduced into the United States probably in Seattle, Washington during the early 1900's and gradually spread through Washington, Oregon, Idaho and into southern British Columbia during the 20^th Century. Concurrent with the expansion in range, there have been reports of necrosis in humans allegedly caused by bites from Loxosceles reclusa Gertsch & Mulaik 1940 (which does not occur in the Pacific Northwestern U.S or Canada) or T. agrestis. The geographic range of T. agrestis now extends into Montana, Utah, Nevada and most recently, central and southwestern Wyoming.