COLEOPTERA. 
491 
THE FIFTH ORDER OF INSECTS,— 
COLEOPTERA, Linn. (Eleutherata, Fabr.),— 
Have four wings, of which the upper pair is crustaceous, in the form of scales, horizontal, 
and meeting [when at rest] along the inner edge by a straight line. They have, likewise, 
mandibles and maxillae, and the lower wings are folded only transversely, and covered by the 
other two, which form a kind of case, and which are generally known under the name of elytra. 
These insects [generally known under the English name of Beetles] are the most numerous 
and the best known of the insect tribes. Their singular forms, the brilliant colours exhibited 
by many of their species, the size of their bodies, the more solid texture of their teguments, 
which renders their preservation much more easy, and the numerous advantages to be derived 
from the investigation of such a variety of forms of their external organs, have merited for 
them the particular attention of naturalists. 
The head is provided with two antennae of variable form, and of which the number of joints 
is generally eleven ; two facetted eyes ; no ocelli ; and a mouth composed of an upper lip, two 
mandibles, mostly of a scaly consistence, two lower jaws (maxillae), each bearing one or two 
palpi, and a lower lip formed of two pieces, namely, the mentum and the tonguelet {languette), 
and accompanied by two palpi, generally inserted upon this latter piece ; those of the 
maxillae, or the outer maxillary palpi (when they bear two), have never more than four joints, 
whilst those of the low'er lip have, ordinarily, only three joints. 
The anterior segment of the trunk, or that which is in front of the wings or elytra, and 
which is commonly named the corselet [prothorax], and which bears the first pair of feet, 
and greatly surpasses in extent the two other segments, which are compactly united together, 
as well as to the base of the abdomen : their under part, or the sternum or breast, serves 
as a point of attachment to the two other pairs of feet.* The second of these segments [or 
the mesothorax], upon which is placed the scutellum, is narrower in front, so as to form a 
short peduncle, which is received into the inner cavity of the first segment [or prothorax], 
and w^hich serves as a pivot to assist in all its movements. 
The elytra and wings arise upon the lateral and superior margins of the hinder division of 
the thorax, [or the meso- and metanotum]. The elytra are crustaceous, and in repose are 
applied one against the other in a straight line along the inner margin, or suture, and are 
always in a horizontal position. In almost every instance they hide the wings, which are 
large, and folded transversely. Many species are wingless ; but the elytra are always present. 
The abdomen is sessile, or united to the thorax by its greatest width : it is composed on the 
outside of six or seven segments ; membranous above, or of a consistence less firm than on 
the under side. The number of joints on the tarsi varies from three to five.f 
Beetles undergo a complete metamorphosis. The larva resembles a worm, with a scaly head 
and mouth, analogous in the number and functions of its parts to that of the perfect insect, 
and also with six legs : some species, however, few in number, are destitute of these appen- 
dages, or have only simple fleshy tubercles. 
The pupa is inactive, and does not take any nourishment. The habitation, mode of life, 
and other habits of these insects, both in their immature and perfect states, vary very much. 
I have divided this order into four sections, after the number of joints of the tarsi. J 
* The mesothorax is always narrow and short, and the metathorax, 
often of larger size, is longitudinally impressed down the centre. 
t Judging from analogy, the Coleoptera described as monomerous 
have probably three joints to the tarsi, but of which the two basal 
joints escape the view : this section, as well as the Dimera, have been 
suppressed in this edition. 
J [The distribution of the Coleoptera, founded upon the number of 
joints in the tarsi, has been objected to by some authors, as it has the 
effect, if rigidly adhered to, of separating certain groups nearly related 
together : as, for instance, the Pselaphidae (which have only 3-jointed 
tarsi), and the Staphylinidae, which have 5-jointed tarsi. Some 
species are also anomalous in the number of the joints of their tarsi 
varying in the sexes. Another objection has been raised to the tarsal 
system, on the ground, that the so-called Tetramera have, in effect, 
I 5-jointed, instead of 4-jointed tarsi ; and the Trimera, 4-jointed, and 
not 3-jointed tarsi, as those names indicate. But these objections 
appear to me insufficient ; due allowances must be made for certain ex- 
ceptions against every rule ; and the peculiar structure of the tetrame- 
rous or trimerous tarsi,equally merits their retention as distinct groups. 
Mr. M'Leay has proposed a classification of the Beetles, founded upon 
