118 GENERAL CHARACTERS OF BEETLES. 



the cabinets of collectors ; and we may safely affirm, that at least 

 as many more yet remain to be discovered. 



639. The conversion of the first pair of wings into elytra^ or 

 hard wing-cases, and the complete in closure of the second pair 

 by these, when the insect is at rest, constitute, as we have seen, 

 the distinguishing features of the Order. The elytra, when 

 expanded, are of little or no use in flight, generally remaining 

 nearly motionless ; when closed, they meet along the back in a 

 straight line, which is called the suture. The structure of the 

 mouth, in this order, has been already described. The head is 

 provided with two antennas, which vary in form, but which have 

 usually eleven joints ; the form of these often differs considerably 

 in the two sexes. The eyes are large and protuberant, espe- 

 cially in the carnivorous species, and in those, the slowness of 

 whose habits makes them need quick powers of sight, for the 

 purpose of avoiding their enemies. Of the three segments of the 

 thorax, the anterior one (commonly termed the corslet) greatly 

 surpasses the two others in size ; being so much developed at 

 their expense, as almost to constitute the thorax by itself. The 

 two latter segments are firmly united to each other, and to the 

 commencement of the abdomen ; and the chief movement of the 

 parts of the trunk upon one another, is between the first and 

 second segments of the thorax ; the latter being prolonged for- 

 wards into a sort of footstalk, which is received into a cavity in 

 the former, and thus serves as a kind of pivot for its movements. 

 The abdomen usually consists of only six or seven segments ; the 

 remainder of the nine, which properly form this part, being 

 consolidated in the last. 



640. Although the characters already mentioned are applica- 

 ble to by far the greater number of insects included in this Order, 

 nearly all of them are subject to exceptions. Thus, there are 

 many species, in which the organs of flight seem altogether 

 wanting, in one sex, at least, as in the female Glow-worm ; even 

 here, however, the rudiments of elytra will be found. In other 

 instances, the elytra are fully developed, so as to cover the upper 

 surface of the body ; but adhere together along the suture, so as 

 to prevent the expansion of the wings, which are, consequent! v. 



