52 PARTIAL ORISMOLOGY. 



The exact description and knowledge of the oral organs is of great 

 importance in Systematic Entomology, as these parts supply the charac- 

 ters of many genera, and not rarely of entire families: we must, con- 

 sequently, here give a very precise definition of their forms. 



In the first place we must distinguish the BITING organs (instr. cib. 

 mordent ia, s. libera) from the SUCKING ones (instr. cib. suctorict) ; 

 and the former are also specially called MASTICATING organs (instr. 

 masticandi) ; these stand freely beside each other, and display much 

 uniformity in their structure as well as great regularity of shape *, 

 whereby they announce a superior degree of development, so much so, 

 that insects with a masticating mouth, notwithstanding its very 

 similar conformation, take the precedence of those with suctorial organs. 

 The latter are more or less united together, and assume very different 

 shapes in the several orders, of which we shall particularly treat below- 



The masticating mouth (as found in the Coleoptera, Dictyotoptera, 

 Neuroptera, and many Hymenopterci) consists of the following organs : 



The upper lip, LABRUM, (labrum, labium superius, PI. III. f. 11. i), 

 is very generally of the form of a segment of the circle, or a triangular, 

 or quadrangular, somewhat convex corneous plate, which is united 

 posteriorly by a membranous hinge with the clypeus. Fabricius f 

 originally called this organ clypeus, in which he was followed by Illi- 

 ger {. This latter writer applied the name of labrum to the narrow 

 anterior appendage of the true labrum, which is very seldom present, 

 but is found in some of the Hymenoptera (Hylceus), and is called by 

 Kirby and Spence the APFENDICLE (appendicula}. 



The upper jaws or MANDIBLES (mandibulce, PI. III. f. 11 13. o, o), 

 which are two strong, corneous, somewhat bent hooks, their inner 

 margin being more or less dentate ; and which articulate with the 

 cheeks at their broad basis, and move by ginglymus, opposed to each 

 other like the blades of scissors. 



The under jaws or MAXILLA (maxillae, PI. III. f. 12 and 13, P, P), 

 are also a pair of organs which in many respects resemble the mandibles, 

 although smaller and more delicately constructed. They are not simple, 

 but distinctly consist of four pieces. The two first hang attached to 



* See what Kirby and Spence say upon their variety, Introduction to Entomology, 



vol. iii. p. 473 ; what Burmeister says above must be taken comparatively TR. 



j- Philosoph. Entom., p. 37. + Terminologie, p. 220. 



Burmeister says it is the genus Hylaus, without indicating that he means of Fabricius. 

 I know it only in the females of the genus Halictus, which are comprised in the above 

 genus of Fabricius TR. 



