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 



to. 



FIG. 611. Ventral aspect of a beetle, Enchroma gigantea: f, 

 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; 

 14', prpsternum; 15, mesothorax; 15', mesoepisternum; 15', 

 mesoepimeron; 15', mesosternum; 16, metathorax; 16", meta- 

 episternum; i6 f . metaepimeron; 16', metasternum; i6 11 , ante- 

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

 17", trochanter; 17, femur; i7 d , tibia; 17', tarsus; 17'", tarsal 

 claws; i7 ea , 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- 



