446 



COMPARATIVE ANATOMY 



CHAP. 



1. The upper lip (labrum Ibr) is an unpaired piece which covers 

 the oral aperture in front and from above, and has nothing* to do with 

 the limbs. 



2. The Mandibles (upper jaws, md) consist on each side of a 

 powerful but unsegmented masticatory plate with toothed edge. 



3. The anterior maxillae (lower jaw). Each of these 2 maxillae 

 consists of a 2-jointed basal portion (mx^, which carries first a 

 5-jointed feeler (pin, palpus maxillaris), and second, 2 un jointed 



771 X. 



Fig. 303. Mouth parts of Blatta (Orthoptera, after Savigny). Ibr, Labrum (upper lip) ; md, 

 mandible; mx 1} anterior pair of maxillae; mx. 2 , posterior pair of maxillae = lower lip (labium); st, 

 stipes (stem) ; m, mentum ; sm, submentum ; mi and me, mala interna and externa, inner and outer 

 ridges of the 1st and 2d pairs of maxillae ; pm, palpus maxillaris, feeler of the anterior maxillae ; pi, 

 palpus labialis, feeler of the posterior maxillae. 



masticatory ridges, one outer (me, mala externa) and one inner (mi, 

 mala interna). 



4. The posterior maxillae together form the lower lip (labium, mx 2 ). 

 Each posterior maxilla consists of the same parts as the anterior 

 maxillae (basal part, 3-jointed feeler pi, outer and inner masticatory 

 ridges me and mi), but the 2 basal parts on each side have grown 

 together behind and below the mouth in the middle line. 



These mouth parts are adapted for biting and chewing. 



We shall now describe the most important modifications of the above type in 

 systematic order. 



