. 1NSECTA. 



never exhibited, in this class, by the mandibles. Their extremity is 

 often terminated by two divisions or lobes, the exterior of which, in the 

 Orthoptera, is called the galea. We have already said that the upper 

 lip was called the labrnw. The other, or the labium properly so styled, 

 is formed of two parts ; the one, inferior and solid, is the menlitm or 

 chin ; the other, which is usually provided with two palpi, is the 

 lignlfi. 



In the Sucloria, or those that live by the suction of fluid aliment, 

 these various organs of manducation present themselves under two 

 kinds of general modifications. In the first, the mandibles and the 

 jaws are replaced by little lamina? in the form of setae or lancets, form- 

 ing, by their union, a sort of sucker, which is received into a sheath, 

 supplying the place of a labium, and is either cylindrical or conical, and 

 articulated in the form of a rostrum, or fleshy or membranous, inarti- 

 culated, and terminated by two lips constituting a proboscis. The 

 labrurn is triangular and arched, and covers the base of the sucker. 



In the second modification, the labrum and mandibles are nearly 

 obliterated, or are extremely small : the labium is no longer free, and 

 is only distinguishable by the presence of two palpi, to which it gives 

 insertion : the jaws have acquired a most extraordinary length, and are 

 transformed into tubular filaments, which, being united at their edges, 

 compose a sort of spiral proboscis called the tongue, but which, to avoid 

 all equivocation, it would be better to call spirignntha ; its interior 

 exhibits three canals, the intermediate of which is the duct of the ali- 

 mentary juices. At the base of each of these filaments is a palpus, 

 usually very small, and but slightly apparent. 



The Myriapoda are the only insects in which the mouth presents 

 another mode of organisation it will be explained in treating of that 

 order. . 



The trunk of insects, or that intermediate portion of their body 

 which bears the legs, is generally designated by the term thorax, or 

 corselet by the French. It is composed of three segments, not well 

 distinguished at first, the relative proportions of which vary consider- 

 ably. Sometimes, as in the Coleoptera, the anterior, much the largest, 

 separated from the following one by an articulation, moveable, and alone 

 exposed, appears at the first glance to constitute the entire trunk, and 

 is called the thorax or corselet ; sometimes, as in the Hymenoptera, 

 Lepidoptera, &c., it is much shorter than the ensuing one, has the 

 appearance of a collar, and, with the two others, forms a common body, 

 attached to the abdomen by a pedicle, or adhering closely to it across 

 its whole posterior width, and is also called thora.v. These distinctions 



