THE ANATOMY OF IX SECTS. 



13 



less convex, and their mesal surface concave. Usually each mandible consists 

 of a single segment; but in some insects these organs are much more com- 

 plicated. 



In several genera of Rove-beetles [Staphylinidce) each mandible is furnished 

 with an appendage (Fig. 23). This was named the prosthcca by Kirby and 

 Spence. 



Fig. 23. — Mandible of Staphylinus. 



Fig. 24. — Mandible of Euphoria inda. 



In many beetles of the family Scarabaeidae each mandible consists of several 

 more or less distinct sclerites. This is vvel. shown in the mandible of Euphoria 

 inda (Fig. 24). These compound mandibles have not yet been studied with 

 sufficient care to enable us to definitely name the parts. 



The Maxilla. — The maxillae (11) are the more ventral of the two pairs of 

 jaws. They are much more complicated than the mandibles, each maxilla 

 consisting, when all of the parts are present, of five primary parts and three ap- 

 pendages. The primary parts are the cat-do or hinge, the stipes or footstalk, 

 the palpifer or palpus-bearer, the subgalea or helmet-bearer, and the lacinia or 

 blade. The appendages are the maxillary palpus or feeler, the galea or superior 

 lobe, and the digitus or finger. The maxilla may also bear claw-like or tooth- 

 like projections, spines, bristles, and hairs. 



In the following description of the parts of the maxillae, only very general 

 statements can be made. Not only is there an infinite variation in the form of 

 these parts, but the same part may have a very different outline on the dorsal 

 aspect of the maxilla from what it has on the ventral. Compare Fig. 25 and 

 Fig. 26, which represent the two aspects of the maxilla of Hydrophilus. Except- 

 ing Fig. 26, the figures of maxillae represent the ventral aspect of this organ. 



Fig. 25 —Ventral aspect of 

 maxilla of Hydrophilus. 



Fig. 26. — Dorsal aspect of 

 maxilla of Hydrophilus. 



Fig. 



Maxilla of EUodes. 



The Cdrdo or hinge (a) is the first or proximal part of the maxilla. It is 

 usually more or less triangular in outline, and is the part upon which nearly all 

 of the motions of this organ depend. In many cases, however, it is not the 



