COLEOPTERA. 
495 
mesothorax often bear a striking resemblance to elytra (this 
can be well-seen by removing the scales from the paraptera, 
orpatagia, as they are termed, of a sphinx moth); and the 
fact that in many Coleoptera ( e.g. y Dytiscus) what appear to 
be rudiments of the fore wings exist beneath the elytra. 
The argument based on the thickened structure of the 
elytra loses its force when we consider the more or less elytra¬ 
like wings of many other insects (Heteroptera, certain Blatti- 
dae, et al .); and it probably would not have been seriously 
urged but for the presence of the so-called rudimentary wings 
beneath the elytra of certain beetles. These, however, have 
been found to correspond in structure and position to the 
alulae of the wings of other insects; but most important of 
all, a study of the development of elytra has proven that they 
are wings. 
The hind wings are membranous, and in most species very 
efficient organs of flight. But in some of the pre-eminently 
running beetles the hind wings are wanting, and the elytra 
serve only as a protection to the abdomen. With some of 
these insects the elytra are even grown together where they 
meet on the middle line of the back. Instances of this kind 
are not uncommon among the ground-beetles and the dark¬ 
ling beetles. 
The different mouth-parts are very evenly developed; 
we do not find some of them greatly enlarged at the ex¬ 
pense of others, as in several other orders of insects. The 
upper lip, or labrum, is usually distinct; the mandibles are 
powerful jaws fitted either for seizing prey or for gnawing; 
the maxillae are also well developed and are quite compli¬ 
cated, consisting of several distinct pieces; the maxillary 
palpi are usually prominent; and the lower lip, or labium, is 
also well developed and complicated, consisting of several 
parts and bearing prominent labial palpi. 
The larvae are commonly called grubs. They are usually 
furnished with six thoracic legs, and often with a single 
proleg at the caudal end of the body; some, however, as 
