598 EXTERNAL ANATOMY OF INSECTS. 



except at their base, are armed with little teeth, alter- 

 nating with each other like the cogs of a mill-wheel. In 

 apterous beetles the elytra are often connate, or have 

 both sutures as it were soldered together. The margin 3 

 or external edge of the elytra is generally formed by a bead 

 or ridge, which, except in the case of the truncated ones, 

 in which it is straight, curves more or less from the base to 

 the apex; this ridge is often recurved so as to form a kind 

 of channel between it and the disk of the elytrum, as may 

 be seen in the Dynastidce : in some there are two parallel 

 ridges, as in Copris; in Silpha the margin is dilated; in 

 Helceus and Cossyphus it is remarkably so and recurved, 

 so that, in conjunction with those of the prothorax which 

 are similarly circumstanced, they give the animal some re- 

 semblance to a small model of a barge. Though the margin 

 of elytra is most commonly intire, yet in some beetles, as 

 Gynmopleurus Illig., a sinus is taken out of it; in Cetonia 

 it often projects at the base, and in Cryptocephalus in the 

 middle, into a lobe ; in Phoberns MacLeay it is denticu- 

 lated, and in many Buprestes more or less serrulated ; 

 sometimes it terminates before it reaches the apex of the 

 elytrum in a tooth, as in many Carabi Latr. The epi- 

 pleura b or side-cover is that part of the organ in ques- 

 tion, below the margin, with which it usually forms an 

 angle, being more or less inflexed, that covers the sides 

 of the body. It varies in different tribes, being some- 

 times obsolete, as in the weevils [Curculio L.); in the 

 Capricorn beetles it is very narrow; in Carabus, &c, 

 dilated at the base ; in many Heteromerous beetles, as 

 Blaps, Pimelia, &c, it is very wide and conspicuous ; in 



a Plate X. Fig. 1, c. * Plate XXVIII. Fig. 6—8. d"' . 



