392 THE TRANSITION TO LAND 



character to some extent, but it is quite distinctive in the pit vipers. In- 

 dividual characteristics of the pit vipers found in the United States are 

 as follows. 



The rattlesnakes are by far the most abundant and important of the 

 poisonous snakes in the United States. They are nervous, tempera- 

 mental snakes that are quick to strike and carry a very potent poison. 

 These snakes are best known by the rattle which consists of a series of 

 rings of dried skin on the tip of the tail. When a person gets excited 

 and nervous his hands often tremble ; snakes do not have any hands, so 

 their tails tremble when they are excited. When the tail trembles at 

 high speed the rattle makes a characteristic whirring sound that is easily 

 recognized after it has once been heard. When the skin is shed a ring 



Photo by Winchester 



Fig. 26.15. Rattlesnake poison. This innocent looking pile of crystals, about a half 

 an inch in diameter, contains the crystallized poison extracted from thirty rattlesnakes. 



of the posterior part of it is left behind to form a ring of the rattle. It 

 is sometimes said that a rattlesnake's age can be told by the number of 

 rings on the rattle. This is not accurate, for the snake may shed its 

 skin from one to three times a year and the rings are sometimes broken 

 off. Another superstition holds that a rattlesnake always rattles before 

 striking. They rattle when they get excited but if you suddenly step 

 on one that may be sleeping it will strike immediately without waiting 

 to rattle. 



The fangs are long and curved and fold back against the roof of the 

 mouth in a sheath of skin when not in use. When danger threatens the 

 snake will probably try to get away first, but if pressed closely will pull 

 itself into loose loops facing its foe ready to strike. As the snake strikes, 

 the lower jaw is dropped down, the fangs become erect, and the head hits 

 with enough force to drive the fangs into the flesh. At the moment they 

 enter, the poison sacs contract and inject the poison and the snake jerks 

 its head back ready to strike again. All of this takes place with light- 



