176 METAMonrnosEs of animals. 



The muscles, which before were uniformly distributed, (159,) 

 are now gathered into masses. The limbs are elongated, 

 and wings spring forth from the thorax. More active motions 

 then reappear in the digestive organs, and the animal, burst- 

 ing the envelop of its chrysalis, issues in the form of a winged 

 moth. 



370 The different external forms which an insect may 

 assume is well illustrated by one which is unfortunately too 

 well known in this country, namely, the canker-worm. Its 

 eggs are laid on posts and fences, or upon the branches of our 

 apple-trees, elms, and other trees. They are hatched about 

 the time the tender leaves of these trees begin to unfold. 

 a b e d 



Fig. 147. 

 The caterpillar {a) feeds on the leaves, and attains its full 

 growth at the end of about four weeks, being then not quite 

 an inch in length. It then descends to the ground, and en- 

 ters the earth to the depth of four or five inches, and having 

 excavated a sort of cell, is soon changed into a chrysalis or 

 aiymph, {h.) At the usual time in the spring, it bursts the 

 sivin, and appears in its perfect state, under the form of a 

 /noth, (J.) In this species, however, only the male has 

 .vings. The perfect insects soon pair, the female (c) crawls 

 up a tree, and, having deposited her eggs, dies. 



371. Transformations no less remarkable are observed 

 among the Crustacea. The metamorphoses in the family of 

 virrhipedes are especially striking. It is now known that 

 he barnacles, y^Balanus,) which have been arranged among 

 J he mollusks, are truly crustaceans ; and this result of modern 

 lesearches has been deduced in the clearest manner from the 



