144 METAMORPHOSES OF ANIMALS. 



mass in the chest. Antennas and palpi are developed on 

 the head, and simple eyes are exchanged for compound ones. 

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

 are now gathered into masses. The limbs are elongated, 

 and wings spring out from the thorax. More active motions 

 then reappear in the digestive organs, and the animal, 

 bursting 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 near the tips of the small branches of the 

 apple-tree, elm, and some other trees. They are hatched 

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



a b c 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 

 enters the earth to the depth of four or five inches, and 

 having excavated a sort of cell, is soon changed into a chry- 

 salis or nymph (&). At the usual time in the spring, it bursts 

 the skin, and appears in its perfect state, under the form 

 of a winged moth (d). In this species, however, only the 

 male has wings. The perfect insects soon pair, the female 

 (c) crawls up a tree and deposits her eggs, and then dies. 



371. Transformations no less remarkable are observed 

 among the Crustacea. The metamorphoses in the family Cir- 

 rhipedes are especially striking. It is now known that the 

 barnacles (Balanus), which have been arranged among the 



