BRANCH ARTHROPODA; CLASS IN SECT A : THE INSECTS 191 



most of the internal organs of the larva (fig. 55) and a 

 rebuilding of the organs of the adult from primitive be- 

 ginnings. 



The habits of the larvae of insects with complete meta- 

 morphosis and of the young of some insects with incom- 

 plete metamorphosis often differ markedly from the 



FIG. 55. A cross-section of the body of the pupa of a honey-bee, showing 

 the body cavity filled with disintegrated tissues, and (at the bottom) a 

 budding pair of legs of the adult, the larva being wholly legless. 

 (Photo-micrograph by Geo. O. Mitchell.) 



habits of the adults, and as the habits and instincts of 

 insects are remarkably specialized, the study of their be- 

 havior and of the structural and physiological modifica- 

 tion which their varied habits of life have brought about 

 is of much interest and significance. In later paragraphs 

 this phase of insect study will be again referred to. 



Classification. Much attention has been paid to the 

 classification of insects and the 300,000 (approximately) 

 known species have been variously grouped together into 

 orders by different entomologists. A subdivision of the 

 class Insecta into five orders was proposed by Linnaeus 

 about 1750 and was used until comparatively recently. 

 Since then, however, numerous other arrangements have 

 been proposed, all of them agreeing in increasing the 



