COLEOPTERA, 



503 



are greatly developed ; they project from the body wall, with which 

 they are hinged, and constitute the wing-covers or elytra. The par- 

 aptera of the mesothorax are concealed. 



Each sternum or ventral part of each thoracic segment is composed 



Fig. 611. — ^Ventral aspect of a beetle, Enckroma gigantea : /, 

 head; 2% gena of the epicranium; 3, eye; 7, antenna; //, 

 thorax; 14, prothorax; 14% proepisternum or episternum of 

 the prothorax; 14^ , proepimeron or epimeron of the prothorax; 

 141, prosternum; 15, mesothorax; 15®, mesoepisternum; 15^, 

 mesoepimeron; 15*, mesosternum ; 16, metathorax; i6«, meta- 

 episternum; i6^ metaepimeron ; i6», metasternum; i6»i, ante- 

 coxal piece of the metasternum; 17^ coxa; 17*^, trochantin; 

 17^, trochanter; 17®, femur; 17'*, tibia; 17^, tarsus; 17*1, tarsal 

 claws; 17^2, pulvilli; 18, elytron. 



of a single sclerite (Fig. 608, /.) As indicated above, the three sterna 

 are designed as the prosternum, mesosternum, and metasternum, 

 respectively. 



In some beetles the metasternum is divided into two unequal por~ 



