EXTERNAL ANATOMY OF INSECTS. 605 



either for food, repose, or to lay their eggs ; to promote 

 this purpose more effectually, the wings are usually cu- 

 riously folded and laid up under them; and where the 

 elytra are very short, as in the Staphylinidce, these folds 

 are very numerous and complex. In some instances, 

 however, as in Molorchus F., Atractocerus, &c, the wings 

 are only partially protected by the elytra and not folded 

 under them; probably they are less in danger of laceration 

 from their peculiar habits than the generality. Another 

 use is to protect the upper-side of the alitrunk, which for 

 reasons before assigned is usually softer than the under- 

 side, and also of the abdomen, often above nearly mem- 

 branous, from the injury to which they would otherwise 

 be exposed ; in the latter part also the spiracles in Co- 

 leoptera are not covered by the inosculations of the seg- 

 ments, as is the case in most other Orders, and therefore 

 probably require some covering when the insect is not 

 flying. . In the Apterous beetles this appears to be their 

 principal use ; where these organs are connate, or as it 

 were soldered together, the back of the abdomen is a 

 thin membrane ; the appearance of two elytra in these 

 cases is given, doubtless, for the sake of symmetry and 

 beauty, a subordinate attention to which may be traced 

 in all the works of creation. If we consider the bulk and 

 weight of many flying beetles, we may imagine that they 

 want some assistance, more than the extent and dimen- 

 sion of their wings seem to promise, to support them in 

 the air, and to enable them to move more readily in it ; 

 and although it seems clear from the state of their mus- 

 cular apparatus that elytra do not move much in flight, 

 yet by giving a broad and concave surface to the air, for 

 then they are usually nearly vertical, they may assist in 



