8 GUIDE TO CALIFORNIA INSECTS 



Concluding processes. 



12. Completion of expansion of wrinkled parts by blood pressure produced 

 by filling the air sacs and by the contraction of the muscles of the body wall. 



13. Hardening of cuticle on exposure to the air. 



14. Beginning of feeding. 



15. Completion of oxidization of skin pigment. 



Metamorphosis is the term used to express the changes an insect undergoes 

 from the time it hatches from the egg until it assumes the adult condition. 

 In the more primitive insect it is not very striking. In those that possess 



Figure 2. Photograph of a vine hopper just molted, and of the skin from which 

 it came. 



wings the change on becoming adult is very much more evident. The 

 somnus just preceeding the last molt is longer and the whole thoracic 

 structure is reorganized to provide the hinge and musculation necessary 

 fOf flight. When the change to the adult becomes so profound as to extend 

 the somnus over the entire instar preceeding the acquirement of adult 

 structures we have a third type of metamorphosis. This inactive and non- 

 feeding stage, the pupa, usually becomes very different externally from the 

 larva. The development of complex metamorphosis permits a simultaneous 

 improvement in the adaptation of both the young and the adult insect. 

 Insects having this kind of metamorphosis greatly outnumber all others. 



