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 diseus- 
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 Moceasins, and Crotalus, Rattlesnakes, are 
about equally to be 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 
