IXSECTS. 



241 



The second method of subdivision depends upon the 

 facts of life-history. In the first or amctabolous group the 

 young leaves the eggs with the general shape and appear- 

 ance of the adult, the chief difference being that of size. 

 In the second or hcmimctabolous division the young upon 

 leaving the egg differs from the adult in the lack of wings. 

 During growth the skin is often molted, and with each 



FIG. 67. Life-history of the Colorado potato-beetle (Doryphora de ce.mUneatcf) . 



a, eggs; b, larva; c, pupa; d, adult. 



molt the wings increase in size until at last the adult 

 condition is reached. In the third or holometdbolous group, 

 a form, the larva, hatches from the egg, which differs 

 greatly from the adult. This increases greatly in size 

 but without marked change in appearance, until, at a 

 single molt, it changes its appearance completely and 

 becomes a pupa, in which condition it remains quiescent 

 until by a final molt the adult characters are assumed 

 (fig. 67). These changes constitute a metamorphosis. 



