CHARACTERS OF IRE COLXOfTE&A. 297 



The illustration on p. 281 will suffice to explain the divisions of the body of a Coleopterous insect, 

 and the parts of its upper, or dorsal, surface. The insect is represented as divided into four parts, viz., 

 (1) the head; (2) the pro-thorax (bearing the anterior pair of legs); (3) the ineso- arid metathorax (bear- 

 ing the intermediate and posterior legs, the wing-covers, and the wings) ; and (4) the abdomen. This 

 last in the living insect is, however, usually closely attached to the metathorax, forming with it and 

 the mesothorax the so-called " hind body." The mouth consists of a labrum, or upper lip ; a mentum, 

 or chin; a lower lip, immediately adjoining the mentum, and two pairs of jaws, viz., the upper, 

 or mandibles, and the lower, or maxillae ; the latter and the labiuni bearing each a pair of small-jointed 

 appendages called palpi. All these parts are subject to a wide range of modification, which furnishes 

 not only a guide to the food and habits of the insects, but to their classification, the form of the 

 different parts of the mouth being amongst the most constant characters of the genera and families. 

 Throughout all the modifications, however, it is to be noted that the labium, or lower lip, never 

 assumes the form it does in the order Orthoptera, where it shows a division into two lobes, or blades, 

 indicating its fundamental condition, in the lower annulose types, as a third pair of mouth-appendages, 

 bearing the labial palpi on the sides. In Coleoptera, the lower part of the labium is much 

 contracted in size, and the upper part, forming the ligula, or tongue, is an undivided horny or 

 coriaceous plate. This difference is important, as constituting one of the chief signs of the higher 

 specialisation of the Coleopterous order. Besides the mouth, the under-surface of the three segments 

 of the thorax requires the attention of the student. Each segment beneath is normally divided into 

 five parts, or plates, separated from each other by tine sutures, the middle plate protruding a narrow 

 lobe between the articulating cavities, or sockets, of each pair of legs, and the side pieces (two on each 

 side, called episternum and epimeron) being of various shapes according to the genera. The form of 

 these breast-plates, or sternums, especially the various shapes of the processes between the haunches 

 of the legs and the extent to which they take part in forming the rim of the haunch-sockets, constitute 

 most trustworthy guides in ascertaining the natural relationship of the genera and families. The 

 abdomen is composed of a series of rings, or segments, each having its dorsal and its ventral plate, or 

 segment, the spiracles, or breathing-holes, being on or near the points of junction of the two plates. 

 The legs are composed of (1) a haunch, which articulates with the body ; (2) a small narrow appendage, 

 on the inner side at its apex, called the trochaiiter ; (3) the femur, or thigh ; (4) the tibia, or 

 shank ; and, lastly (5), the tarsi, or foot, consisting of a number of joints, differing according to the 

 great primary divisions of the order, and bearing a pair of claws at their tips. 



With regard to the stages through which Beetles, like all true insects, have to pass before reaching 

 the winged adult state, we have already said that their development is by complete metamorphosis, 

 that is, the intermediate stage between the active, feeding, larva and the adult, variously called in 

 the different orders, pupa, nymph, or chrysalis, is a period of quiescence, the insect being encased, 

 trunk and limbs, in a membranous or horny integument, and having time and repose sufficient for the 

 elaboration of the great change taking place in nearly all its parts. The metamorphosis, however, is 

 not so complete as in the Lepidoptera (Butterflies and Moths), the swaddling-cloth of the pupa not 

 forming a simple case, but separately covering body and limbs. The larva varies very greatly in 

 form in the different families; it is generally elongated, clothed with a tough skin, and furnished 

 with six feet, in which case it has often a tolerably close resemblance to the perfect insect, 

 minus the wings ; but in some large groups it is a footless maggot, and, again, in a few parasitic 

 genera it is an active hexapod in one stage of its growth and a maggot in another. In all its 

 forms, however, it has a distinct head, and thus may be distinguished from the often similar larvse 

 of Dipterous insects. Viewing the order generally, it may be said that the larva is less unlike the 

 adult and the metamorphosis less complete, than in the Hymenoptera and Lepidoptera, and that 

 the Coleoptera must therefore rank as a less perfect or specialised type than either of those orders 

 of insects. 



Amidst all their great diversity of forms and habits, the Coleoptera offer no example of those 

 wonderful social and architectural instincts which excite our admiration in Bees, Wasps, and Ants of 

 the order Hymenoptera. and of White Ants in the Orthoptera. Neither are there any instances of a 

 third, or neuter class of individuals, such as we see in the social species of the above-named orders. 

 No clear case even of co-operation among the individuals of a species is known ; the nearest approach 

 228 



