GENERATION, SEX AND ONTOGENY 



235 



or the animal is said to undergo or to show metamorphosis in 

 its development. 



This metamorphosis is familiar to all in insects; to zoologists, 

 it is familiar among numerous other kinds of animals. Fig. 138 



FIG. 138. Metamorphosis of the Monarch butterfly, ^4 nosia plexippus: a, Egg; b, larva; 



c, pupa; d, imago, or adult. 



shows the different stages in the metamorphic development 

 of the common large red-brown milkweed butterfly, Anosia 

 plexippus. From the egg hatches a crawling, wormlike larva, 

 wingless, without compound eyes, and with strong jaws and 

 other mouth parts fitted for biting. This creature develops 

 into the winged butterfly with different eyes, different antenna 1 , 

 different mouth parts, different almost everything. And, by 

 the intervention of a curious quiescent stage called the pupal 



