136 THE BOOK OF A NATURALIST 



tongue," says Lacepede in his Natural History of 

 Serpents, "is to catch insects, which it catches by 

 means of its double tongue." This notion about 

 the use of the double tongue is quite common 

 among the older ophiologists, and, along with it, 

 the belief that snakes prey chiefly on insects. And 

 here I cannot resist the temptation to quote a few 

 more words touching on this point from Lacepede 

 — a very perfect example of the teleological spirit 

 in science which flourished a century ago, and made 

 things easy for the naturalist. " We are not," he 

 says, " to be amazed at the vast number of serpents, 

 both species and individuals, which inhabit the 

 intertropical countries. There they find the degree 

 of warmth which seems congenial to their natures, 

 and the smaller species find abundance of insects to 

 serve them for food. In those torrid regions, where 

 Nature has produced an infinite multitude of 

 insects and worms, she has likewise produced the 

 greatest number of serpents to destroy the worms 

 and insects ; which otherwise would multiply so 

 exceedingly as to destroy all vegetable productions, 

 and to reduce the most fertile regions of the earth 

 into barren deserts, inaccessible to man and animals ; 

 nay, even these noxious and troublesome insects 

 would be finally obliged to destroy each other, and 

 nothing would remain but their mangled limbs." 



Here the French naturalist pauses, aghast at the 

 frightful picture of desolation he has himself con- 

 jured up. 



When enumerating the uses to which a serpent 



