464 



ARTHROPODA. 



The labium arises as a pair of processes which early approach each 

 other and fuse behind the mouth. All the parts of the maxilla 

 may be recognized, only it must be remembered that the basal 

 parts of the two sides are fused. The united cardines form an 

 under chin, the submentum, the stipites a chin or mentum, which 

 in the Orthoptera is cleft, a result of incomplete fusion. This 

 may bear inner and outer processes, the glosscv (gl) and the para- 

 glosses (pg) respectively, and the labial palpus. The mandible con- 



FIG. 486. FIG. 487. 



Fio. 486. Chewing mouth parts of cockroach (Periplaneta orientalis). The letter- 

 ing is the same in figs. 486-489. c, cardo ; gl, glossa ; /it/, hypopharynx ; I, lobe ; 

 le, li, external and internal lobes of maxilla; Zr, labrum ; m, memtum ; md, man- 

 dible ; mx, maxilla ; p, pm, maxillary palpus ; pg, paraglossa ; pi, labial palpus ; 

 sm, submentum; st, stipes. 



Fio. 487. Licking mouth parts of bumble bee (Bombus terrestris). 



sists of merely the basal joint, altered for biting, while the rest of 

 the appendage, common in Crustacea as the mandibular palpus, is 

 lacking. 



The licking mouth parts, like those of the bees (fig. 487), stand 

 next to those already described, there being many transitional 

 stages. Labrum and mandibles retain their primitive condition, 

 while maxillae and labium are greatly elongate, are connected at 

 the bases, and can be folded away beneath the head or extended at 

 will. The small submentum is followed by an elongate mentum 



