'9 



Mandibles. — Below the labrum-epipharynx are the strong- 

 ly chitinized prominent manJihles. Each mandible is a single 

 sclerite, toothed on its distal or biting surface. 



Maxillae.— Lying next to and below the mandibles are 

 the viaxilli^.. The cardo is small and elongate, subtriangular 

 in shape and divided into two parts by a transverse line. 

 The stipes is larger, and subquadrangular. Articulating with 

 the stipes are the five-segmented maxillary palpus^ and the 

 two terminal lobes, the galea and the lacinia. The galea 

 forms a sort of hood for the smaller triangular lacinia and is 

 composed of two segments. The lacinia ends in a sharp, 

 strong chitinous tooth. Indications, only, of the suture set- 

 ting off the palpiger can be discovered in the maxilla of the 

 cockroach. 



Labium. — The labium is a single flap-like structure, which 

 lies below the maxilla, and forms the floor of the mouth. It 

 is, although an unpaired organ, really formed in all insects 

 by the fusion of two organs similar in character to the 

 maxillae. The labium is sometimes called, because of this 

 homology of structure, the second maxillae. 



In the cockroach the proximal or articulating sclerite, the 

 subtnentum, is large and shows no indication of its paired 

 origin. The succeeding sclerite, the mentiim, is smaller and 

 also is without indication of an original bipartite condition. 

 Arising from the mentum, however, are the two four-seg- 

 mented labial palpi and four terminal lobes ; two of these 

 lobes and a palpus belong to each lateral half of the mentum 

 and correspond to the lacinia, galea, and palpus, respectively, 

 of the maxillae. The inner lobes of the labium are called 

 glossce and the outer ones, paraglossce. The glossae and para- 

 glossae are fused so that only their distal portions are free 

 and distinct. This fusion of the terminal lobes of the labium 

 is carried farther among most other insects. Often the 

 paraglossa and glossa of each side will fuse completely so 



