XXVI INTRODUCTION. 



It is believed that one joint is .added to the number each year; this is but 

 approximately true; there are variations connected with the different ages 

 and rates of growth, the extent of which have not been fully determined. 

 The joints are so easily worn out and broken that it is seldom the case that 

 a large snake has the complete series. 



The probable use of the organ has given rise to a great deal of discus- 

 sion. Because of the resemblance of the sound to the crepitation of the 

 grasshopper, and to the shrilling of the Cicada or harvest fly, though much 

 less rapid in its vibrations than the latter, it is claimed that it draws insect- 

 eating birds within reach. This is possible; but the fact that the snakes are 

 usually so quiet when feeding, and that birds are so rarely found in their 

 stomachs, bears against the supposition. The idea that the rattle produces 

 terrorism in the prey is hardly tenable, since it appears to be least used 

 when feeding, and frightens the game away. The rattles are used in time 

 of coupling, but not with the energy marking their use in anger. In reality, 

 the attitude of the serpent is defensive at all times, unless it be when seek- 

 ing food; it prefers to economize venom and take no risk of losing fangs; it 

 does not wish to strike unless driven to do so; and the rattling is a threat 

 or warning that it is ready if it must. In economizing venom and fangs 

 the rattle is undoubtedly beneficial, and prevents a great many useless 

 strokes; at the same time its action is disadvantageous in that it calls the 

 attention of enemies to its owner. A snake appears to realize how much 

 its subsistence depends on an ever ready supply of venom and perfect 

 fangs, and how helpless it becomes without them. 



It is often asserted that deer destroy a great many snakes. On what 

 foundation the assertion rests I do not know. Hogs are certainly fond of 

 them, and large fowl are especially destructive to the young. 



Ancistrodon, Copperheads and Moccasins, and Crotalii*, Rattlesnakes, are 

 about equally to lie feared. These genera properly belong to North America. 

 Five species of Rattlesnakes are found East of the Mississippi. 



Certain species having plates on the crown resembling those of the 

 Colubers have been given the generic names Crotalophorus, Caudisona, and 

 Crotalus by different authors. These names were synonymous at a time 

 when the species of which we speak were unknown. They were originally 

 applied to species which have not been separated from the genus as first 

 constituted. In view of this, it seems best to regard them as synonymous, 

 and to give to the species with the shields a name less liable to confuse on 



