118 STORY OF THE REPTILES 



takes effect. The warning is similar in purpose to 

 that of bright warning colors seen in the brilliant 

 snakes, some stinging insects, and in Belt's little frog 

 already noted. We have seen that many harmless 

 snakes imitate a rattle by vibrating an ordinary tail 

 against a leaf, whereby doubtless they hope to terrify 

 a foe. One serpent has rough serrations (or teeth- 

 hke notches) on its side-scales ; and by rubbing the 

 folds of the body together back and forth a sort of 

 mechanical hiss is made which is a threat — perhaps at 

 times a call. Any snake makes a husky rattling noise 

 as its coils rub past each othei' in its excitement. 



Other reptiles have rude voices — there being, it 

 is said, some evidence of vocal cords in the geckos. 

 Crocodiles are well known to have voice, bellowing 

 being a very loud form of challenge by the males ; 

 and the mother and young each have a distinct cry. 

 The tortoise-forms hiss or breathe audibly when dis- 

 turbed, and they perhaps have a slight voice. 



In this connection it may be noted that many 

 reptiles evidently play with each other, but it is 

 usually in their courting antics where this prevails. 

 Turtles have mock-fights between the sexes, and the 

 male alligator makes a silly exhibition of himself in 

 the presence of his mate by either turning round and 

 round on land or circling in the water, which he 

 churns threatenino^ly with his tail, to show her how 

 he would treat a rival should one come near. Dr. 

 Merriam reports two snakes seen in the act of rear- 

 ing up and apparently playing with each other. 



It is quite evident that lizards romp with each 



