NUTRITION PROPER. 



333 



divided and masticated by the jaws working toward one 

 another laterally (not vertically, as in vertebrates). 



m*fi 



nvx.p 



Fig. 213. — The mouth parts of a grasshopper enlarged : Ibr, labrum ; m m, 

 mandibles ; lb, labium ; Ip, labial palpi ; /, tongue ; mx mx, maxilla? ; 

 mxp mxp, maxillary palpi. 



Serial Homology of these Parts.— As already 

 said (page 273), the insect head consists of four segments 

 with their paired appendages. The labrum is an exten- 

 sion downward of the first segment, and the antenna; are 

 the jointed appendages; the mandibles are the paired 

 appendages of the second segment; the maxillae, the 

 paired appendages of the third segment; while the la- 

 bium and its paired appendages belong to the fourth 

 segment (Fig. 215). 



