CLASSIFICATION OF THE ANIMAL KINGDOM. 121 



are Wasps, Bees, etc. The eighth order, Goleoptera, or Beetles, with a 

 pair of dense horny anterior wings, and a thin posterior pair, folded up 

 when not in flight, whose larvae possess heads and sometimes feet. 



Having thus specified the orders, the author proceeds next to a descrip- 

 tion of the anatomy of perfect insects; and as regards their legs, instead 

 of the stiff appendages of the last class — Myriofioda, we find a beautiful 

 structure composed of five portions — the coxa or hip, the trochanter, the 

 femur or thigh, the tibia or shank, and the tarsus or foot, which last is 

 again divided into a variable number of jointed segments. Some insects 

 are provided with hooks on the last joint of the tarsus, others with a single 

 claw like the Louse, (Pediculus,) others again have flaps or suckers, and 

 thick pulvilli, to enable them to climb vertical polished surfaces. The 

 thighs of the posterior legs of some insects are greatly enlarged, to 

 enable them to leap; others, by the enlargement of the tibia and other 

 parts, possess the power of burrowing under the ground, while the legs of 

 some swimming insects resemble oars. As regards their means of flight, 

 the wings, which are invariably attached to the two posterior segments of 

 the thorax, are very variable in their shape and structure, some have four, 

 some two, and some none at all. 



The outer integument of insects, which in this respect resembles the skin 

 of vertebrate animals, consists of three distinct layers — the epidermis, the 

 rete-mucosum, where the colouring lies, and the cutis or true skin; and 

 each wing is only a kind of prolongation of this common covering, and 

 is "composed of two delicate films of the epidermis, stretched upon a 

 strong and net-like framework." Many insects are also provided with 

 other appendages, such as spines, hair, scales, etc. The muscular system 

 of this class is highly developed, particularly in the legs and wings. Their 

 mouths are wonderful instruments, and are either mandibulate or haustellate, 

 the former, or perfect mouth, consists of an upper lip, (labrum,) an under 

 lip, (labium,) two upper jaws, (mandibulae,) and two under jaws, (maxillae,) 

 both pairs of which work horizontally; the lower lip is divided into two 

 portions — the mentum, or chin, and the tongue. Besides these there are 

 also some curious appendages inserted upon the maxillae and labium, called 

 palpi, or feelers. The suctorial or haustellate mouth, though it differs 

 very much in outward appearance from the last, yet the parts composing 

 it are fundamentally the same as those met with in the mandibulate class. 

 These last mouths vary considerably. The Hemiptera, for instance, have 

 four lancets, which are only the mandibles and maxillae altered in shape, 

 and they are enclosed in a sheath, the base of which is covered by a small 

 scale; and these answer, the one to the labium, and the other to the 

 upper lip of mandibulate insects; and the same general order is found 

 throughout. 



