THE DEVELOPMENT OF INSECTS 



31 



FIG. 15.- 



Typical Pupa of a Sphinx 

 Moth. 



The casting of the pupal skin and the emergence of the 

 adult constitutes the final moult in the cycle where the 

 development is indi- 

 rect. The life cycle is 

 completed with the 

 laying of eggs by these 

 adults. 



26. The Purpose 

 of Metamorphosis. 

 The purpose of meta- 

 morphosis, especially the complete type, is explained as 

 are other specializations. It seems to be to the advan- 

 tage of the insects to have the diiferent vital functions 

 performed at 

 dLTerent pe- 

 riods of the 

 life of the in- 

 sects instead 

 of all at the 

 same time. 

 The larval 

 stage is de- 

 voted to 

 feeding and 

 growth and 

 the storage of 



food material for the adult stage. The pupal stage is solely 

 for change in form and structure to adapt the insect for 

 the functions of the adult which are reproduction and 

 spread. 



There are intermediate forms of metamorphosis. In 

 these the nymph may not resemble the adult even to 

 such a degree that it may be recognized. However, 



FIG. 16. Larva of Imperial Moth 



