An adult female Dermacentor variabilis (American dog tick)

Champman AS, Bakken JS, Folk SM, et al. Diagnosis and management of tickborne rickettsial diseases: Rocky Mountain Spotted Fever, Ehrlichoioses, and Anaplasmosis-United States: A practical guide for physicians and other health-care and public health professionals. MMWR Recomm Rep 2006; 55(RR-4):1.