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 metathorax are concealed. 



Each sternum or ventral part of each thoracic segment is composed 



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

 head; 2% gena of the epicranium; 3, eye; 7, antenna; 77, 

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

 the prothorax; i4 f , proepimeron or epimeron of the prothorax; 

 14'. prosternum; 15, mesothorax; is e , mesoepisternum; i5 f , 

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

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

 coxal piece of the metasternum; 17", coxa; 17 s1 , trochantin; 

 :7 b , trochanter; 17°. femur; i7 d , tibia; i7 e , tarsus; i7 el , tarsal 

 claws; i7 e2 , pulvilli; 18, elytron. 



of a single sclerite (Fig. 608. z.) 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- 



