28 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO7 



of the frontoclypeal area of the head (fig. 8 A) anterior to the frontal 

 gangHon (FrGng). The large hypopharyngeal muscles (tig. 8 A; tig. 

 13 D, hplimcl), on the other hand, arise hehind the frontal ganglion 

 connectives ; they are inserted on a pair of broad platelike lobes of 

 the sitophore, representing the oral arms of the hypopharynx in other 

 insects (fig. 2 D ; fig. 13 A, F, _v). 



Neuroptera {Megaloptera and Planipennia). — The arms of the 

 cleavage line on the head of neuropterous larvae go always mesad of 

 the antennae in the manner characteristic of most Ilolometabola, and 

 at their greatest extent they cut entirely through the clypeal area. 

 On the adult head the cleavage line is absent. 



The Megaloptera, including Raphidia, show very clearly the inter- 

 antennal position of the frontal arms of the cleavage line (fig. 10 A, 

 D, G). In the larva of Sialis (D) there is present a fully developed 

 epistomal sulcus {es) setting off the clypeus from the frontal area 

 behind it, and the arms of the cleavage line end at this groove. In 

 Corydalus (A), Chauliodes (C), and Raphidia (G), however, the 

 epistomal sulcus is represented only by short lateral grooves (A, es', 

 es') containing the anterior tentorial pits (at, at), and in these forms 

 the frontal arms of the cleavage line extend through the clypeal area 

 to the distal margin of the latter. At ecdysis, as seen in Cliauliodes 

 (C), the frontal clefts cut out a triangular frontoclypeal apotome 

 (frcapt). The frontoclypeal nature of the apotomal triangle is shown 

 by the origin of the labral and hypopharyngeal muscles on its upper 

 part (A, Ibrmcls, hphmcl) and the attachment of the cibarial muscles 

 (dlcb) on its lower part. In the larva of Sialis, in which the epistomal 

 sulcus is complete (D), these same groups of muscles, as shown by 

 Rober (1941), arise respectively on the frontal and clypeal areas of 

 the prospective apotome. 



The adult megalopteran head is like the larval head with respect to 

 the development of the epistomal sulcus, the sulcus being complete in 

 the imago of Sialis (fig. 10 E, F, es) as it is in the larva (D), but 

 interrupted between the tentorial pits in Corydalus (B), Chauliodes, 

 and Raphidia as it is in the larvae of these forms (A, C, G). The line 

 of exuvial cleavage in the larval cuticle, however, is suppressed in the 

 adults of all these latter genera (B). The adult head of Sialis presents 

 a median groove that forks anteriorly into a pair of weakly impressed 

 lines (E, F, incs) diverging behind the antennal bases. Though these 

 grooves of the imaginal head of Sialis are regarded by Rober (1941) 

 as the "coronal suture" and the "frontal sutures," Rober notes that 

 the latter do not have the position of the frontal lines of the larva, 

 which he says are preformed lines for rupture of the cuticle at ecdysis. 



