. Bulletin. Natural history; Natural history. I November, 1961 Smith: Amphibians and Reptiles of Illinois 269. '^^Jit»jip'' Fig. 249.—An adult Sistrurus catenatus catenatus from Piatt County, Illinois. The ground- color is gray, tan, or light brown ; the blotches are dark gray or dark brown. Table 89.—Sexual variation in Illinois Sistrurus catenatus catenatus. Figures in paren- theses are numbers of specimens. Characteristic Males (8) Females (10) Range Mean Range Mean Ventrals 138-145 27-31 30-35 5-7 138-151 22-29 29-40 4-6 Caudals . . . Bod
. Bulletin. Natural history; Natural history. I November, 1961 Smith: Amphibians and Reptiles of Illinois 269. '^^Jit»jip'' Fig. 249.—An adult Sistrurus catenatus catenatus from Piatt County, Illinois. The ground- color is gray, tan, or light brown ; the blotches are dark gray or dark brown. Table 89.—Sexual variation in Illinois Sistrurus catenatus catenatus. Figures in paren- theses are numbers of specimens. Characteristic Males (8) Females (10) Range Mean Range Mean Ventrals 138-145 27-31 30-35 5-7 138-151 22-29 29-40 4-6 Caudals . . . Body blotches Tail rings . Tail length as percentage of total length gradient from north to south is suggested when the average number of dorsal blotches of specimens from central Illinois is com- pared with that of specimens from south- western Illinois. Fifteen specimens from the central part of the state have 23 to 40 (aver- age ) dorsal blotches; seven specimens from Madison and Fayette counties have 26 to 34 (average ). Individual variation in a sample of 18 specimens is as follows: anterior scale rows 25 in 29 per cent of specimens, 26 in 29 per cent, 27 in 35 per cent, and 28 in 6 per cent; scale rows at mid-body are 24 in 12 per cent, 25 in 70 per cent, 26 in 12 per cent, and 27 in 6 per cent; posterior scale rows are 18 in 18 per cent, 19 in 82 per cent. Some vari- ation in darkness of groundcolor is apparent, but, in the course of this study, no melanistic specimens have been found. Kennicott (1855), however, mentions a black example from Cook County. Habits.—Although this small rattle- snake occurs in bogs and other wooded areas, the preferred habitat is probably prairie or old fields with heavy bluegrass cover. Specimens are occasion- ally found under objects such as logs or grain shocks, but most individuals are en- countered sunning themselves on clumps of grass or crossing roads. Several of these snakes have been caught in snap tr
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