112 



THE UNIVERSE. 



they would require only a very short time to devour all the 

 vegetation on the globe. 



The first period of an insect's life is devoted to develop- 

 ment, to nutrition, and frequently it is only during this 

 time that it eats in the gluttonous manner we have just 



55. Head and Jaws of the Willow-Eating Caterpillar. From Lyonet's Anatomical Treatise. 



spoken of. When it has reached its full development, it 

 seems to have no other object in its existence than repro- 

 duction ; sometimes even the alimentary canal is obliterated, 

 and the animal takes no nourishment. The caterpillar, 

 with its destructive jaws, the ruin of our harvests, is trans- 

 formed into a butterfly, the harmless proboscis of which 

 only imbibes the nectar of flowers. 1 In its last stage the 

 Ephemera lives on love alone ; its digestive apparatus has 

 quite disappeared. 



Some Hemiptera are, however, all through life extremely 



1 See a more special reference to this form of metamorphosis at page 134. 



