EXTERNAL ANATOMY OF INSECTS. 603 
the various retreats to which these animals betake them- 
selves either for food, repose, or to lay their eggs; to 
promote this purpose more effectually, the wings are 
usually curiously folded and laid up under them; and 
where the elytra are very short, as in the Staphylinide, 
these folds are very numerous and complex. In some 
instances, however, as in Molorchus, Atractocerus, &c., 
the wings are only partially protected by the elytra and 
not folded under them; probably they are less in dan- 
ger of laceration from their peculiar habits than the ge- 
nerality. 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 abcve nearly membranous, from the injury to 
which they would otherwise be exposed; in the latter 
part also the spiracles in Coleoptera are not covered by 
the inosculations of the segments, as is the case in most 
other Orders, and therefore probably require some co- 
vering 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 ap- 
pearance of two elytra in these cases is given, doubtless, 
for the sake of symmetry and beauty, a subordinate at- 
tention 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 as- 
sistance, more than the extent and dimension 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 muscular apparatus 
that elytra do not move much in flight, yet by giving a 
