AMNH. American Museum of Natural History. CAS. California Academy of Science. CM. Carnegie Museum. Chic. AS. Chicago Academy of Science. Clev. MNH. Cleveland Museum of Natural History. LMH. Collection of Lawrence M. Huey. JKJ. Collection of J. Knox Jones, Jr. CMNH. Colorado Museum of Natural History. FM. Chicago Museum of Natural History. HM. Hastings Museum, Hastings, Nebraska. ISC. Iowa State College. MCZ. Museum of Comparative Zoology. MO. University of Missouri Museum of Zoology. MVZ. Museum of Vertebrate Zoology, Berkeley, Calif. NMC. National Museum of Canada. NGFP. Nebraska Game, Forestation, and Parks Commission. NCS. North Carolina State College. OHIO. Ohio Wildlife Research Unit, Ohio State University. OKLA. Oklahoma Agricultural and Mechanical College. PM. Provincial Museum of British Columbia. ROM. Royal Ontario Museum of Zoology. SDM. San Diego Natural History Museum. SITC. Southern Illinois Teachers College. USBS. United States Biological Surveys Collection. USNM. United States National Museum. UCM. University of Colorado Museum. UIM. University of Illinois Museum of Natural History. UM. University of Michigan Museum of Zoology. UU. University of Utah Museum of Zoology. The species are arranged from least to most progressive, and the subspecies are arranged alphabetically. The synonymy for each subspecies includes first a citation to the earliest available name then one citation to each name combination that has been applied to the subspecies and, finally, any other especially important references. Marginal records of occurrence for each subspecies are shown on the maps by means of hollow circles and these localities are listed in clockwise order beginning with the northernmost locality. If more than one of these localities lies on the line of latitude that is northernmost for a given subspecies the western-most of these is recorded first. Marginal localities have been cited in a separate paragraph at the end of the section on specimens examined in the account of a subspecies. Localities that are not marginal are shown on the maps by solid black circles. Localities that could not be represented on the distribution map because of undue crowding or overlapping of symbols are italicized in the lists of specimens examined and in the lists of marginal records.