VARIATION IN THK COMMON GARTER-SNAKE. 175 



VARIATION IX THE (M)MMOX (JAKTEK-SXAKK iTHAMXOPHIS 



SIRTALIS). 



W. L. SrEKRY. 



The results of the iuvestigatioii suniniarfV.ed in this paper represeut 

 work carried on during the spring and early summer of 1!)02 upon the 

 variations in the common garter-snake. The reasons which led to the 

 work may be stated brietly as follows: Cope in his exhaustive work on 

 the Ophidia of North America has carried his classification into sub- 

 species so far that the amateur naturalist becomes hopelessly confused 

 in trying to locate many of the forms and the zoologist is often at a 

 loss to know just where to place a certain specimen. The attention of 

 the writer of this paper was jiarticularly called to this in trying to 

 place some of the garter-snakes which were picked up near Olivet and 

 were difficult to classify satisfactorily from Cope's work in which he 

 gives eleven sub-species of Tliamiiopliis i^irtalis, the only appreciable dif- 

 ference between them being the matter of coloration. The variations 

 are largely a matter of relative shades of brown and green on the back, 

 and blue or green on the belly, and the distinctness of the stripes and 

 spots on the back. The only absolute distinction of color seems to be 

 the introduction in many of the individuals, of a series of red blotches 

 just below the lateral stripes, which are common in many garter-snakes 

 and which are familiar to any one who lias noticed their coloration. The 

 color changes so frequently, even in a single individual, varying with 

 the freshness of the skin, and in preserved specimens (from which Cope 

 largely worked), with the quality and strength of the preservative, that 

 it seemed there ought to be some further differences in the number of 

 gastrosteges (stomach plates) and the number of urosteges (tail plates), 

 or perhaps in relative measurements, to justify the subdivisions Cope 

 has made. Hence the work was undertaken with a view of finding, if 

 possible, some correlation between color, and proportions and scale var- 

 iation. As the investigation went on it became evident that the results 

 were largeh" negative, but a most interesting set of statistics upon the 

 relative variation of the sexes was obtained and the work drifted largely 

 into that channel. The outline followed in the work and in this paper 

 is identical with the outline which Dr. Clark followed in his investiga- 

 tion of the common water-snake {Natrix fasciata sipe<lon) and the red 

 bellied black-snake (Xatri.r cri/throf/nfitrr) , the results of which are em- 

 bodied in a paper published in the "American Naturalist"" for January, 

 1903. 



The natural history of the garter-snake is so well known that we need 

 hardly tarry over it. As Cope says: "This species ranges all over 

 North America, being limited to the north by its capacity for enduring 

 cold and extending south to Guatemala." It is probably the most com- 

 mon snake in the northern and eastei-n United States and is found in 

 nearly every locality and in the most varied surroundings. During the 

 period when the snake is shedding its skin, i. e., the late spring and 



