178 NORTH AMERICAN INSECTS. 



present condition and extent at least, produce suffi- 

 cient nourishment to sustain us, or them. 



After it has attained its full growth, the caterpillar 

 stops eating, casts its skin and becomes a chrysalis or 

 cocoon (Pupa.) Some suspend their cocoons from the 

 branch of a tree, as for instance, the Asterias, others 

 bury themselves in the ground, as do all the Hawk- 

 moths, and in this condition remain throughout the 

 cold winter season. Thus the chrysalis passes its life 

 in a state of torpor, without eating or moving, until 

 after a shorter or longer period it bursts its skin, and 

 the perfect butterfly, or moth, issues, no more to in- 

 jure vegetation, because it has exchanged its mouth 

 for a spirally rolled tongue, with which it can only 

 suck the juices of plants and flowers. 



In this metamorphosis, some very great changes oc- 

 cur in the appearance and beauty of the insect, as well 

 as in its form and structure. Some of the handsomest 

 caterpillars issue from their cocoons the plainest,even 

 the ugliest looking butterflies, and vice versa. Thus 

 the potatoe-worm is remarkable for its beautifully va- 

 riegated colors, but when it becomes adult as a hawk- 

 moth, it has a unform dingy gray color. But the con- 

 trary is often the case, and an insignificant looking 

 caterpillar is as often metamorphosed into a very hand- 

 some butterfly. 



Such changes, however, are not confined to insects, 

 but are also common throughout the animal kingdom, 



