l6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO3 



IX. DASCILLOIDEA 



From this superfamily adult and immature stages of Nosodcndron 

 calif ornicum Horn, Nosodendridae, and Heterocerus sp., Hetero- 

 ceridae, larvae were studied. In the adult Nosodendron (figs. 50, 

 51, 52), of the labral muscles only the ventral muscle of the labrum, 5 

 (figs. 51, 52), is present. The cibarial, pharyngeal, and hypopharyn- 

 geal muscles are well developed. The muscle of hypo pharyngeal bar 

 Y, 10 (figs. 51, 52), is especially massive. Bar Y (fig. 52) is greatly 

 modified ; it forms a strong, lateral support to the mouth and is con- 

 tinuous with a broad, thin, sclerotized structure that extends ven- 

 trally and posteriorly to become united- with the ventral head wall. 

 The dorsal and ventral muscles of the labium, 20 and 21 (figs. 50, 52), 

 are present ; they originate in the gular area posterior to the submen- 

 tum. The mentum completely covers the prementum in this species 



(fig- 52). 



In the larval Nosodendron (figs. 53, 54, 55) the labral muscles are 

 absent as is also the compressor muscle group of the cibarium, 12 

 (fig. 54). The dorsal dilator muscles of the cibarium, 5, 6, and 7, 

 the muscle of hypo pharyngeal bar Y , 10, and the dorsal dilator muscles 

 of the pharynx, p and 11, are all massive and are collected more or 

 less in the region of the posterior area of the cibarium (figs. 53, 54). 

 Bar Y (fig. 54) is large and forms a strong support on the sides of 

 the mouth; it extends ventrally on the sides of the posterior hypo- 

 pharyngeal region. The full complement of labial muscles is present. 



In Heterocerus the labral, cibarial, pharyngeal, and hypopharyngeal 

 muscles are similar to those of Nosodendron; the muscle of hypo- 

 pharyngeal bar Y is trifurcate. The dorsal muscle of the labium, 20, 

 arises at the posterior end of the anterior tentorial arms and is 

 inserted on the dorsal wall of the labium at what is probably the base 

 of the hypopharynx. The ventral muscle of the labium, 21, takes its 

 origin medially in the posterior region of the postmentum and is 

 inserted medially at the base of prementum i. Muscle 22 (probably 

 the muscle of the prementum) originates on a transverse bar that 

 connects the anterior tentorial arms; it is inserted laterally in the 

 posterior region of prementum 2. 



X. DRYOPOIDEA 



Helichus fastigiattis (Say), Dryopidae (figs. 56, 57, 58), is the 

 adult form selected for study from this superfamily. The muscula- 

 ture in this species is, with some modification, of the generalized 

 plan. The compressor muscle group of the cibarium, 12, is absent 



