6.5 



COLEOPTERA. 



COLEOPTERA. 



The clypeus is the part to which the labrum is attached, and which 

 is usually on the same plane with it. The term clypeus will seldom 

 lie found in descriptions, excepting in giving the characters of those 

 beetles which belong to the LameUicorncs, a tribe in which this part 

 is greatly developed (fys. 17 and 18, d), and where the labrum is 

 hidden beneath it. 



Under the labrum the mandibles (inandibulic) are situated. These, 

 as their name implies, are the organs of nmndiication ; they move 

 horizontally, and are most commonly of a shape more or less 

 approaching to a triangle. Their form however varies according to 

 the food of the insect. 



Generally speaking, in beetles which feed upon vegetable sub- 

 stances the jaws are broad, obtusely pointed at the apex, and have 

 moreover a broad flat surface at their base (often with little sharp 

 ridges), which somewhat resembles a molar tooth of herbivorous 

 quadrupeds. (Fig. 21.) In those species whose habits are carnivo- 

 rous the jaws are longer and less stout, have the apex acutely pointed, 

 and several sharp tooth-like processes on their inner side. (Pig. 20.) 



Next in succession follow the maxilla;, or under jaws (fig. 17, n, and 

 fig. 22) : these organs are situated beneath the mandibles, and, like 

 them, move horizontally. A typical maxilla consists of several parts, 

 the principal of which are the hinge (cardo), a piece situated at the 

 Lase of the maxilla (fig. 22, d) ; the maxillary palpus (fig. 22, a), an 

 articulated organ generally composed of four joints ; the outer lobe 

 (lobim superior), which in beetles of carnivorous habits is a two-jointed 

 process (Jig. 22, 4) situated between the maxillary palpus and the 

 inferior lobe (lobus inferior), which last portion constitutes the inner 

 part of the maxilla, and is often formed like the blade of a knife, and 

 furnished generally with a series of bristles or hairs on the inner edge. 

 (Fig. 22, c.) The maxillae seem to be used with the labium in direct- 

 ing the food during manducation, and the bristles on the inner edge 

 appear to serve as a kind of strainer through which the juices are 

 pressed, for we observe that solid substances are seldom swallowed by 

 insects in their imago state. 



The labium, or under lip (fig. 17, i and g, and/</. 23 and 26), is 

 a moveable organ which serves to close the mouth beneath, and is 

 generally divided by a transverse suture, in which cane the lower 

 portion constitutes the mentum, or chin. The tongue (fig. 23, c), 

 which may be considered as a portion of the labium, in Col-opterous 

 Insects, is usually situated at the apex of that member, or emerging 

 from it. The labial palpi (fig. 28, I, b, and fig. 1 7, /) are two articu- 

 lated organs usually springing from the summit of the labium on 

 each side. 



Having now briefly noticed the head and its parts, we come to the 

 thorax. On this portion it will be unnecessary to dwell : we need 

 only mention that the thorax in insects tn composed of the three flrst 

 Mgmento of the body, which in the larva state are usually distinct ; 

 these are termed the prothorax, mesothorax, and metathorax ; and it 

 generally happens that in the perfect insect one of these segment* is 

 greatly developed at the expense of the other two, particularly on 

 the upper surface of the body ; such is the case in the Beetle Tribe, 



HAT. HI8T. DIV. VOL. II. 



where the first portion or prothorax (fig. 16, a) and the small plate 

 (fig. 16, b), which is a part of the mesothorax, are all that is visible 

 from above when the elytra are closed. Some few entomologists, 

 therefore, in describing Beetles, call the part (fig. 16, a) the prothorax, 

 but it is most commonly called the thorax. The small plate (fig. 16, 4) 

 above referred to ia called the scutellum, and is usually of a triangular 

 form. 



To the thorax are attached the legs and wings : the anterior pair 

 of legs are attached to the prothorax ; to the mesothorax the inter- 

 mediate pair of legs and the anterior pair of winps, or elytra, as they 

 are termed in the Culeoptera ; and to the metathorax the posterior 

 pair of legs and the hinder pair of wings. Of the wings enough has 

 been said for the present. 



The legs in Beetles vary according to their habits. Thus in some 

 they are formed for running (fig. 27), in others for swimming (fig. 28) ; 

 here they are very broad and flat : in others again their structure is 

 suited to burrowing habits (fig. 29) ; and fig. 30 represents the hind 

 leg of a beetle, which has the power of leaping to a great distance, 

 where the thigh is very large. 



A leg may be divided into five principal parts : the coxa, or hip 

 (rt, fig. 27 and 29), which is the first joint, or that joined to the body, 

 where it plays in a socket ; the next part, or second joint of the leg, 

 is the trochanter (6, fiyi. 27. 28, and 29) ; the third is the femur, or 

 thigh (c, figt. 27, 28, and 29) ; the fourth -joint is called the tibia, or 

 shank (d, figt. 27, 28, and 29) ; the fifth and last part is the tarsus (e, 

 figs. 27, 28, and 29) : this part in a great portion of the Coleopterous 

 Insects is composed of five joints ; in many a lesser number is found, 

 but in none do they exceed five : the last joint of the tarsus is usually 

 terminated by two hooked claws called unguiculi (g, fig. 27), and the 

 apex of the tibia is furnished generally with two straight spines called 

 the calcaria (/, figs. 27 and 28). 



As regards the classification of the Coleoptera, as well as of insects 

 in general, in almort every work which treats of the subject, a new 

 method is proposed. We shall content ourselves however with 

 noticing two that which is most commonly adopted on the conti- 

 nent, and that which is followed by most entomologists of our own 

 country : the former is the method proposed by Latreille, and the 

 latter by Stephens. 



In the classification of the Coleoptera, published by Mr. Stephens 

 in his 'Systematic Catalogue of British Insects,' the various sections 

 and subjections are as follows : 



Order, Coleoptera. 



Sect. 1. Adtphaga. 



Sub-Sect. 1. (jeodephaga. 



2. Hydradephaga. 



3. Philhydritla. 



4. Necrophaga. 

 Sect. 2. Ckilognathomorplia. 



Sub-Sect. 1. Clavicorrux. 



2. LameUicornet. 



3. S/ernori. 



4. Malacodermi. 



Sect. 3, ndminthomorpka. 



Sub-Sect. 1. Ilhinchophora. 



2. Lowrjicornes. 

 Sect. 4. Anoplurimorpha. 



Sub-Sect. 1, Eupoda. 



2. Cyclica. 



3. Trimeri. 

 Sect. 5. Ifeteromera. 

 Sect. 6. Brachelytra. 



The arrangement of Latreille is founded upon the number of joints 

 of the tarsi. He accordingly divides beetles into the four following 

 great sections : 

 Section 1. Pentamera, including all those Beetles which have five 



joints to their tarsi. 

 Section 2. Jleteromera, Beetles with five joints to the tarsi of the 



two anterior pah's of legs, and four to those 



of the posterior pair. 

 Section 3. Tetramera, Beetles with only four distinct joints to all 



the tarsi. 

 Section 4. Trimeri, Beetles with only three distinct joints to the 



tarsi. 



On comparing these two arrangements, it appears that, there is 

 considerable difference of opinion between the authors of them as to 

 the value of certain groups. Ths Trimeri, according to Latreille, is 

 made one of the four great sections, whilst Mr. Stephens makes the 

 same group a sub-section of a tribe of not equal importance with 

 Latreille' s first division, the Pentamera. 



