20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO3 



In Popillia (figs. 75, /6, yy), of the labral muscles only the ventral 

 muscle of the labrum, j (figs. 75, 76), is present. The cibarial, 

 pharyngeal, and hypopharyngeal muscles are similar to those of the 

 generalized plan except that the dorsal dilator muscle of the pharynx, 

 II, is absent. Muscle group /j (figs. 75, 76) may or may not be 

 homologous with the compressor, muscles of the anterior region of 

 the ciharium, ij (fig. 2), in Periplaneta; they are well-developed 

 diagonal muscles inserted on the anterior dorsal wall of the cibarium 

 and they apparently have the same function. The compressor muscle 

 group of the cibarium, 12 (fig. 75), is wide, but not long and it is 

 confined to the posterior dorsal region of the cibarium. There is 

 only one labial muscle present, jp (figs. 76, 77) ; it is a single unit 

 of fibers arising centrally in the middle region of the labium and 

 extending slightly anteriorly and dorsally to become inserted me- 

 dially on the dorsal labial wall. The function, probably, is to assist 

 in moving the hypopharyngeal region in some manner. The levator 

 muscle of the labial palpus, 24 (fig. yy), arises on an intralabral 

 tormalike process extending mesad from the lateroventral base of 

 the labium; this structure extends in a hoop form dorsally and is 

 joined to the process on the opposite side of the labium. The ten- 

 donous insertion end of one of the maxillary muscles enters the in- 

 tralabial region (fig. yy) and extends through the modified, hoop- 

 like structure to be inserted on the maxillary base ; it has no efifect 

 on the movement of the labium. 



In Macrodactylus the median labial muscle, ^p, is absent ; a muscle 

 probably corresponding to the ventral muscle of the labium, 21, of 

 the generalized form arises rather medially in the anterior region of 

 the postmentum and is inserted ventrally on the base of the pre- 

 mentum. The cibarial, pharyngeal, and hypopharyngeal muscles are 

 similar to those in Popillia; the compressor muscles of the anterior 

 region of the cibarium, ij, are absent as is also the ventral muscle of 

 the labrum, 5. 



In Lucanus the median labial muscle, jp, and the ventral muscle 

 of the labrum, 5, are absent ; the ventral muscle of the labium, 21, is 

 similar to that in Macrodactylus. The muscle of hypopharyngeal 

 bar Y, 10, is large and branched because of the fact that bar Y has 

 a wide, thin, multibranched distal end, and muscle 10 is, of course, 

 inserted on these distal branches. There is a muscle group present 

 that possibly is homologous with the compressor muscles of the an- 

 terior region of the cibarium, Jj, in Popillia; the fibers are arranged 

 on the dorsal wall of the cibarium more longitudinally than diago- 

 nally, which is the case in Popillia. The cibaiial muscles are all 



