406 



ARTHROPODA 



\vith a triangular joint, the cardo (c), which is followed by a larger stipes (sf). 

 The stipes in turn supports two chewing lobes, the inner, or lacinia (It), and an 

 outer, or galea (le). The galea may either form a sheath for the lacinia, or, as 

 in many beetles (fig. 470), it may be tactile and jointed again. The stipes also 

 bears the maxillary palpus (pm), consisting of from three to six joints, and is 

 the most leg-like part of the appendage. The labhim arises as a pair of ap- 

 pendages 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, cleft in Orthoptera, a result of 



FIG. 444. FIG. 445. 



FIG. 444. Chewing mouth parts of cockroach (Peri planet a orient alls). The lettering 



is the same in figs. 444-447. C, cardo; gl, glossa; h y, hypopharynx; /, lobe; le, li, external 



and internal lobes of maxilla; Ir, labrum; m, mentum; md, mandible; mx, maxilla; 



p, pm, maxillary palpus; pg, paraglossa; pi, labial palpus; sm, submentum; 5/, stipes. 



FIG. 445. Licking mouth parts of bumble bee (Bombus terrestris). 



incomplete fusion. This may bear inner and outer processes, the glossce (gl) 

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

 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. 445), stand next to those 

 already described, there being many transitional stages. Labrum and mandi- 

 bles retain their primitive condition, while maxilla? 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 

 which bears the unpaired tongue or glossa (gl), which corresponds to the fused 

 glossa; (or to the hypopharynx ?) of the first type and which is used for sucking 



