A 5-in (45 mm) long brown spider with gray markings found in northwestern North America. Males are more venomous than females. A bite causes erythema, blisters, subsequent necrosis of the skin, and sometimes severe, persistent headaches. Systemic corticosteroid therapy may be helpful. Aplastic anemia, intractable diarrhea, or vomiting may occur and, although rare, may be fatal.