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, Enchroma gigantea : /, 

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

 thorax; 14, prothorax; i4 e , proepisternum or episternum of 

 the prothorax; 14', proepimeronor epimeron of the prothorax; 

 14', prosternum; 15, mesothorax; 15, mesoepisternum; is f , 

 mesoepimeron; 15', mespsternum; 16, metathorax; i6 e , meta- 

 episternum; i6 f . inetaepimeron; 16', metasternum; i6 !1 , ante- 

 coxal piece of the metasternum; 17, coxa; 17", trochantin; 

 T7 b , trochanter; i7 c , femur; i7 d , tibia; i7 e , tarsus; 17'', tarsal 

 claws; i7 e2 , 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- 



