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 



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FIG. 138. Metamorphosis of the Monarch butterfly , A 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 antennae, 

 different mouth parts, different almost everything. And, by 

 the intervention of a curious quiescent stage called the pupal 



