EXTERNAL ANATOMY OF THE COLEOPTERA. 



25 



Fig. 7. 



Prosternum of thorax of 

 D. marginalis. 



separate pieces, the prcescutum, scutum, scutellum, and 

 post-scutellum ; but these are 

 all joined together, with no 

 trace of suture in the prono- 

 tum of the Coleoptera. 



The prosternum bears the 

 two front (or anterior) legs, 

 and is divided into three parts, 

 viz. (Fig. 7) a, the sternum; 

 b b, the episterna, and c c, 

 the epimera. The coxa, or 

 hinge-plate of the leg, is seen 

 at d] e is the trochanter ; f, the femur, or thigh; g, the 

 tibia, or shank ; and h, the 

 tarsus, or foot, of which the 

 joints are separately num- 

 bered. The first three joints 

 in the male of Dytiscus mar- 

 ginalis are widened into a 

 round plate, provided with 

 suckers beneath, as will be 

 seen by Fig. 7 ; in which, 

 with the other cuts of the 

 thoracic segments, only one 

 of the limbs is represented. 

 All these figures are, of 

 course, considerably mag- 

 nified. 



The mesothorax, which 

 bears the wing-cases, or ely- 

 tra, and the intermediate " Flg ' 8< 



. , ,, . , .A. Mesothorax of D. marginalis, 



Or middle pair Of legs, IS seen vertically. 



also divided into two por- B. Ditto, seen from above. 



