EXTERNAL ANATOMY OF INSECTS. 595 
pleura, the base and apex, the angles, and the hypoderma. 
At first it should seem as if an elytrum was not like other 
wings divided into areas; but I think upon examination 
it will be found that, though often nearly obsolete, these 
are represented in it ; for the epzpleura* with the recurved 
part of the external margin seems to me analogous to the 
Costal Area; the inflexed part adjoining the scutellum and 
often going beyond it to the Anal, and the rest of the organ 
to the Intermediate. All this you may see in the dung- 
chafer, Geotrupes stercorarius. 'The axis” or pivot by 
which the elytrum articulates with the trunk is generally 
placed about the middle of its base, but nearer the scutel- 
lar than the humeral angle, and varies in length and shape 
in the different tribes, -but not so as to merit particular 
notice ; it may be regarded as composed of three parallel 
pieces, one belonging to each area, that of the costal be- 
ing the longest. In many these pieces are marked by no 
line of distinction, but in Macropus, &c., they may be 
readily traced *. The suture 4 is the znternal margin of 
the elytrum from the point of the scutellum to the end. 
In many beetles the right hand suture, looking from the 
anus to the head, has a lower ledge or margin, and the 
other, one more elevated, which when they are closed 
lies upon the former; in some Dynastide there seems a 
kind of ginglymous structure in this part, each suture 
being fitted with a kind of ridge which is received by 
a channel of the other; in these the suture is generally 
marked out by an adjacent channel: but the most re- 
markable structure of this part distinguishes the genuine 
species of the genus Chlamys, in which both the sutures, 
* Prare XXVHI. Fic. 6—8. d’”’. > Ibid. Fre. 3—5. b!", 
© Tbid. Fic. 3. 4 Pirate X, Fie, 1. cl”. 
20.2 
