Kansas, and from Cedar Bluff Reservoir, 23 miles west and seven miles south of Hays in Trego County, western Kansas, where live-trapping was carried on in 1959 and 1960. Additional data were obtained on numerous field trips to various collecting localities in northeastern Kansas. My first-hand knowledge of the species is also based, in part, on many years of field experience with the far western subspecies _C. c. mormon_ in western Oregon and California, and on similar experience in 1947 and 1948 with the southern subspecies, _C. c. anthicus_ in central Louisiana. This varied field experience with the species at localities well scattered throughout its geographic range has added perspective to the study even though most of the records were collected within a radius of three quarters of a mile. No one locality can be regarded as entirely typical of a species' habitat over its range as a whole. According to my philosophy, the ecological niche of a species is subject to geographical variation analogous to the variation to be seen in the morphological characters of the animal itself. Different community associates, including different competitors, prey, and predators, and different physical factors enforce a somewhat different way of life on a species in geographically remote parts of its range. When analyzed these differences often turn out to have a genetic basis. Thus, limits of tolerance to heat, cold, and drought often vary geographically, and the population density, reproductive potential, seasonal cycle, and other properties of populations may be altered either by the direct effect of the environment, or through its effect on the genetic constitution, produced by natural selection. The local population of racers studied was near the center of the species' geographic range, and is to some extent representative of the species as a whole, though differing in its ecology from other populations in proportion to their remoteness and the distinctness of their habitats. It has not been demonstrated that ecological traits of populations change in a discontinuous manner or correspond in their limits with those of named subspecies. More likely geographical variation is continuous and parallels morphological variation only in a general way. Certainly the boundaries of subspecies' ranges should not be accorded undue emphasis in an ecological study.