INSECTA JAWS. 



523 



L.in 



lobed, or crooked. In the last case the first or second joint is elon- 

 gated forming the shaft, to which the distal and shorter joints are 

 attached at an angle as the flagelluni (Apis). 



The following structures enter into the formation of the mouth 

 parts: the upper lip (labrum), the upper jaws (mandibles), the first 

 pair of maxilla 1 or lower jaws, the second pair of maxilla? or lower 

 lip (labium). The upper lip is a plate, which is usually movably 

 articulated to the cephalic shield and covers the mouth from above. 

 Beneath the upper lip to the light and left are the mandibles or upper 

 jaws, in the form of two 2>(^pless biting plates ; they are unjointed, 

 and therefore more powerful as masticatory organs. The .first pair 

 of maxilla? or lower jaws have a more complicated structure. They 

 are composed of 

 several joints, 

 and are, there- 

 fore, adapted for 

 los powerful but 

 more varied move- 

 ments in aid of 

 the masticatory 

 process. 



The maxilla? of 

 the first pair (fig. 

 430) are made up 

 of the following- 

 parts : a short 

 basal joint (cardo, 

 C), a longer se- 

 cond joint or 

 shaft (stipes, St) 

 with an external scale (squama palpigera), to which is attached 

 a many- jointed palp (paljms maxillaris, Jlxt.). Two blades, an 

 internal and external, are attached to the distal end of the second 

 joint [and known respectively as lacinia and galeci\ (lobus externus, 

 internus, L. in, L. ex). The maxilla? of the second pair arise from 

 the throat, and are partially fused together across the middle line 

 so as to form the unpaired lower lip or labium. It is rarely the case 

 that all the parts of the first maxilla? are discernible in the labium, 

 the fusion being generally accompanied by the reduction and dis- 

 appearance of certain parts. There are, however, cases in which 

 all the elements of the first maxilla- can be shown to exist (Orthop- 



Lr 



FIG. 430. Mouth parts of a lilatfii (after Savifmy). ", Head 

 seen from the front : Oc, ocelli ; Mxt, maxillary palp ; Lf, 

 labial palp, b, Upper lip (labrum, Lr). c, Mandible (Md). 

 d, 1st maxilla : C, Cardo ; Sf, stipes ; L. in, lobus interims ; 

 L. ex, Lobus externus. e, 2nd rnaxillsv or labium (lower 

 lip), clearly composed of two halves. 



