COLEOPTERA 



129 



The mouth-parts. — Much use is made of the form of the parts of the 

 labium or lower lip in descriptions of beetles. When fully developed the 

 labium consists of three principal parts and a pair of appendages. The 

 principal parts are the submentum, the mentum, and the Ugula; the ap- 

 pendages are the labial palpi. The basal part of the labium, the part 

 which is joined to the gula, is the submentum (Fig. 214, sm). By an un- 

 fortunate error this sclerite is almost invariably described in works on 

 the Coleoptera as the 'mentum. This fact should be borne in mind by 

 the student when using any of the older books on this subject. The 

 intermediate portion of the labium is the mentum (Fig. 214, m); and the 

 distal portion the Ugula. 



The ventral aspect of a beetle. — In the classification of beetles much 



Fig. 214. — Labium of Harpalus: sm, sub- 

 mentum; in, mentum; lig, ligula; P, labial 

 palpus. 



Fig. 215. — Ventral aspect of a beetle, Enchroma gigantea: 

 Fig. 214a. — Maxilla of beetle; a, cardo; A, prothorax; B, mesothorax; C, metathorax; c, c, c, coxae; 

 ■ stl .P f r s ; c . palpifer; d, palpus; /, galea; em, em, em, epimera; es, es, es, episterna; s, s, s, sterna; /, I, 

 g, lacinia; /;, digitus. trochantins; x, elytrum; y, antecoxal piece of metasternum. 



use is made of certain sclerites and sutures present on the ventral side 

 of the insect. The student should study Figure 215 to become familiar 

 with these structures. In some beetles the metasternum is divided 

 into two unequal portions by a suture which extends transversely a short 

 distance in front of the caudal margin ; the smaller sclerite which borders 

 the posterior coxas in front and often passes between them is called 

 the ante-coxal piece of the metasterum (Fig. 215, y). 



