30 ELEMtNTS or O-MOJIOLOoY. 



only one pair, they are usually situated on the upper lip ; when two 

 or more, the posterior ones are generally on the lower lip; and in 

 some insects furnished with a sucking trunk, they are oftentimes 

 found inserted at each side of that organ. These feelers are com- 

 posed of several joints, the number of which vary. Like the antennae, 

 to which they bear analogy, they are endowed with powers of motion, 

 but still more extensively. They also serve, like the antennse, as an 

 essential character in the construction of genera ; and from their situ- 

 ation, the number of joints, termination, and relative proportion and 

 size, are exceedingly useful for that purpose. 



Frons, the Front: the anterior or fore part of the head, the space 

 between the eyes and the mouth. 



Clypeus, Shield of the head in coleopterous insects : the part cor- 

 responding with the front of the head in the other orders. In the 

 beetle kind it is advanced more or less upon or over the mouth, and 

 in some forms a sort of cap, the rim of which extends so far over the 

 head as to conceal the mouth beneath. The anterior edge of the c/y- 

 peus is sometimes mistaken for the upper lip. 



Vertex, the Crozon or summit of the Head. 



GuLA, that part which is opposed to the front of the head, usually 

 called the Throat. 



TRUNCUS, the Trunk: the second principal division of which an 

 insect consists, comprehending that portion which is situated between 

 the head and the abdomen. The trunk includes the Thorax, Collar, 

 Sternum, and Seutel. 



Thorax : a term indefinitely applied sometimes to the whole trunk, 

 the seutel excepted : in a stricter sense it implies only the dorsal part 

 of the trunk, and maj^ be considered as expressive of that portion of 

 the superior surface which lies between the head and the base of the 

 wings. The appropriation of suitable terms, by which a thorax con- 

 .sifting of one or of several pieces may be discriminated from each 

 other, is desirable. In some the thorax is of a single piece, as in the 

 orders Coleoptera and Hemiptcra; in that of Lepidoptera it comprehends 

 several segments, and a similar structure is still more conspicuous to 

 view in the order Hymenoptera. The first or anterior segment of the 

 thorax, in those consisting of several pieces, has been sometimes 

 called the collar ; but in admitting this, the coleopterous and hemipterous 

 orders of insects can have no thorax. This will be rendered plain, 

 v'hen we consider that in the latter kinds of insects the first pair of 

 legs arises from what is usually luiderstood by the lower surface of 

 the thorax ; the interior segment, in hymcnopterous insects, corre- 

 sponds with the whole thorax in the former, for the first pair of legs 

 arises from it in exactly the same manner. In the former, the thorax 

 of 3, single piece is immediately succeeded behind by a seutel^ while in 



