CLASS INSECTS. 



SUB-DlVISION. 



ANTHROPODARIA OR ARTICULATED ANIMALS, 



PBOPEELT SO CALLED. 



511. Articulated animals owe their superiority to the 

 class vermes to the superior development of their nervous and 

 locomotive systems, and to the more complete localization of 

 their organs. Some of these characteristic differences have 

 been already pointed out ( 380). The following synoptic 

 table may therefore suffice to recal certain of the characters 

 peculiar to the various groups. 



ARTICULATED ANIMALS, properly so called. 



Aerian respira- 

 tion by tracheae or 

 pulmonary sacs. 



A head distinct 

 Tom the thorax, 

 Burnished with an- 

 tennae. 



/ Body composed of 

 three distinct por- 

 tions, head, thorax, ._ 

 and abdomen ; three f 



-J 



Insects. 



f pairs of feet ; gene- 

 J rally wings. 



I No distinction be- ] 



I tween the thorax and I 



I abdomen ; twenty, j Myriapocla. 



I four pairs of feet or J 



\more ; no wings. / 



Head not distinct from the thorax ; no ' 

 antennae. 



pairs of feet. 



Lrachnides. 



CLASS INSECTS. 



512. To the definition given of this class of animals in 

 the subjoined synoptic table, we have only to add, that they 

 have no vascular system properly so called, and that nearly 

 always they undergo metamorphoses when young. They are 

 the only invertebrate animals organized for flight. 



513. The tegumentary skeleton of insects, that is, the 

 med integuments, preserves sometimes a certain flexi- 

 B B 



