OF THE SKELETON. 151 



num, and above to a membranous space, in which the 

 elytra are fixed. The second ilium is united to the first 

 by its anterior margin ; its inferior margin closes laterally 

 the opening of the mesosternum, which receives the coxa 

 of the second pair of legs ; behind it is united by a mem- 

 brane to the metathorax, and above, to the same mem- 

 branous space as the first ilium. At the point of union 

 between the first and second ilium is a short apophysis, 

 formed by a fold of their margins, to which is articulated 

 the coxa. Superiorly this fold is prolonged, and continued 

 with the anterior margin of the first ilium, sending forth 

 two apophyses ; one is directed inward, forward and down- 

 ward, serving for an attachment to many muscles; the 

 other is shorter, horizontal, and serves as the point of ar- 

 ticulation to the elytra. The metathorax is formed of 

 eighteen parts, ten of which have their analogies in the 

 mesothorax ; its under surface is occupied by a sternum 

 of larger size than that of the mesothorax, but in other 

 respects resembling it : its alee are rhomboidal, and extend 

 from the mesothorax to the COXCB of the last pair of legs, 

 to which they are united by a squamous articulation. The 

 lateral angle of these wings presents a small apophysis, on 

 which are articulated, on one hand, the coxa of the meta- 

 pedes, and, on the other, the second ischium. On the 

 medial line of the sternum rises a stout vertical plate, ter- 

 minated by three long apophyses. On each side of the 

 mesothorax are two parts analogous to the ilia, but diffe- 

 rently formed ; these are the ischia : the second ischium 

 is a flat semioval plate, placed above the wing of the 

 metasternum, occupying its entire width, and united to it 

 by a squamose articulation. Its upper margin is united 

 to the first ischium, which is of a very irregular form, pre- 

 senting behind a quadrangular external part, placed on a 

 level with the second ischium, to which it is united by its 



