RATTLESNAKE 



647 



at the end the dry resonant rattle which has given rise to the common name 

 of the reptile. The coloration of rattlesnakes is apt to be quite variable, 

 even in a single locality. Some individuals may be dark, even nearly black, 

 while others are extensively gray, reddish, or yellowish. 



The rattle of the rattlesnake is a structure which is formed incidentally 

 to the general molt of the outer skin. (See fig. 64). Snakes of all species 

 cast off the outer, worn layer of the skin one or more times each year. 

 In the garter or gopher snakes, in which the tail is tapered to the end, 

 the 'slough' usually comes away in a single piece, being turned inside out 

 as the snake glides out of it, and such cast skins are to be found from 



Bulton 



Fig. 64. Eattle of Pacific Eattlesnake (a) and diagrammatic section of same (&), 

 showing manner in which parts of rattle are held together and yet remain loose enough 

 to permit of movement when tail is vibrated. 



time to time in the field. The molt of the rattlesnake, so far as the body 

 is concerned, is the same as in other snakes. But the tip of the tail in this 

 species is blunt and bears a thickened horny covering with one (later two) 

 constrictions. When the molt occurs, this horny tip is held by the new tip 

 growing beneath it. Successive molts result in a series of these dry seg- 

 ments being formed, each of which is caught over or under the two adjacent 

 ones. The number of segments in a rattle (provided the first small segment 

 or 'button' is still adhering) thus indicates merely the number of times 

 the snake has molted. Large snakes have been found in which only a few 

 segments of the rattle remained, the balance having been worn or broken 

 off. The largest number of rattles which we know definitely to have been 

 found on a rattlesnake was 22. Most individuals have 8 to 10. 



