i88 ELEMENTARY ZOOLOGY 



a few species, too, young are produced parthenogeneti- 

 cally, that is, are produced from unfertilized eggs. And 

 in the case of a few insect species male individuals are 

 not known. 



Development and life-history. The young insect 

 when just hatched from the egg either resembles, except 

 for the absence of wings, its parent in general appearance 

 as in the case of the locust, or it may, as in the butterfly, 

 emerge in a form very unlike the parent. In the first 

 case the young has simply to grow, that is, to increase 



FIG. 52. The young (at left) and adult (at right) of the bed-bug, Acanthia 

 lectularia, a wingless insect with incomplete metamorphosis. (After 

 Riley.) 



in size, to develop wings, and to make some other not 

 very obvious developmental changes in order to become 

 fully grown. But in the case of the butterfly, and 

 similarly in the case of all other insects as the flies, 

 beetles, bees et aL, whose young hatch in a larval condi- 

 tion differing markedly from the adult, some radical and 

 striking developmental changes occur before maturity is 

 reached. Such insects are said to undergo complete 

 metamorphosis in their development, while those insects 

 like the locusts, the sucking-bugs, white ants, and others, 



