28 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO3 



123) has practically disappeared; it is very lightly sclerotized. There 

 is a large, soft suboral lobe, SL (fig. 123), present that extends 

 anteriorly into the cibarium in a tonguelike manner (fig. 123). The 

 labium is furnished with a single pair of muscles (figs. 123, 125) 

 that probably correspond with the inuscle of the prementum, 22, in 

 the generalized form. 



In Dcndroctonous the musculature is similar to that of Pantomorus 

 with a few minor variations. 



Pantonwrus leucoloma Boh, and Listroderes obliquus Klug., Cur- 

 culionidae, and Enpsalis minuta Drury, Brentidae, are the larval 

 species studied. 



In Pantomorus (figs. 126, 127, 128) the ventral muscle of the 

 lahrum, j (fig. 127), and the muscle of hypo pharyngeal bar Y, 10 

 (fig. 127), are very well developed; the cibarial and pharyngeal 

 muscles are rather weak. The pharyngeal muscles, 11 (fig. 127), are 

 probably homologous with the dorsal dilator muscles, 11, in the gen- 

 eralized plan ; they are inserted dor sally on the wall of the pharynx 

 posterior to the frontal connective. Hypopharyngeal bar Y (fig. 127) 

 is continuous with a broad lateral and ventral sclerotized plate that 

 passes beneath the anterior region of the pharynx to become joined 

 with the bar, Y of the other side. A median, flat, sclerotized posterior 

 extension arises from the posterior dorsal margin of the labrum (fig. 

 127, ME) ; it is a resilient piece. When the ventral muscle of the 

 labrum, j (fig. 127), is retracted, the labrum is depressed and the 

 sclerotized dorsal extension, ME, abuts against the posterior inner 

 surface of the epistomal suture (fig. 127, ES). When the ventral 

 muscle of the labrum, j, relaxes, the resiliency of the extended proc- 

 ess, ME (fig. 127), pushes the labrum back into its normal position 

 thus doing the work of a muscle. There is a heavily sclerotized intra- 

 labial rod, IR (fig. 127), present that terminates laterally on the 

 posterior lateral walls of the labium and which is joined to the dorsal 

 labial wall adjacent to the mouth opening. The labial muscles con- 

 form with those of the generalized form in origin and insertion. 



In Listroderes the muscles are essentially the same as those in 

 Pantomorus. The posterior dorsal margin of the labrum is furnished 

 with the median posterior extension, ME, also. The dorsal muscle 

 of the labium, 20, is inserted laterally on the dorsal wall of the labium. 



The muscles in Eupsalis are similar to those of Pantomorus. The 

 dorsal muscle of the labium, 20, is inserted as in the case of Listro- 

 deres. The dorsal dilator muscle of the anterior region of the pharynx. 

 p, is present in this species. 



