70 CLASS V. INSECTS. 



appears in another form without limbs. It ceases to feed or 

 to move. It seems to be totally without life. This is called 

 the chrysalis. After a while, by examining it closely, the imper- 

 fect shape of the butterfly may be distinguished through its 

 surface ; and finally the envelope is broken, and the animal 

 escapes. Its wings are at first short, weak, and moist, but 

 they soon unfold to a greater size, and become strong ; and 

 the insect is in a state to fly. It has now six long legs, a 

 spiral trunk, two antennae, and eyes differing entirely from 

 those of the caterpillar. In short, it is an animal totally dif- 

 ferent ; and yet these wonderful changes are only the succes- 

 sive unfolding of parts contained one within another in the 

 original embryo. 



In the first state, the animal is called the larva; in the 

 second, the nympha or chrysalis ; and the third is called the 

 perfect state. 



A considerable proportion of the insect tribes pass through 

 these three stages of existence. But many only undergo what 

 is called a demi-metamorphosis. Their larva resembles the 

 perfect insect, except that it is without wings. And the only 

 change they experience is, that in the nymph state they have 

 stumps or rudiments of wings, which finally, on casting their 

 skin, are changed into complete ones. Such are grasshoppers 

 and many kinds of bugs. Insects without wings undergo none 

 of these alterations. 



A more detailed account of the phenomena attending the 

 metamorphosis of Insects will be found in a subsequent part 

 of this volume.* 



There are few vegetable substances which escape the dep- 

 redations of insects ; and sometimes their ravages produce 

 very serious evils. Some good as well as evil, however, may 

 be attributed to their agency. Many of them feed upon putrid 

 animal or vegetable matters, whose effluvia might otherwise 

 become dangerous or fatal. Others are made use of in med- 

 icine, in the arts, and sometimes even as food for man. They 

 serve as nourishment for many species of animals. Beasts, 

 birds, reptiles, and fishes, equally make them their prey ; and 

 thus prevent their multiplication to such an extent as to prove 

 a permanent evil to mankind. 



It only remains to give some general account of the orders 

 under which insects have been arranged, and the principles 

 upon which naturalists have proceeded in making the distri- 

 bution of them. 



* See chapter on the Transformation of Animals. 



