30 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, 10/ 



The Y-line on the adult head of Smlis, in fact, is merely a shallow 

 groove of the sclerotic cranial wall, and would appear to have no 

 direct relation to the exuvial cleavage line of the larva. Probably of 

 the same nature is a similar head line in certain other adult Neu- 

 roptera, as that regarded by Ferris (1940) as the persisting "epi- 

 cranial suture" in Plega signata (Hagen). A dried specimen of 

 Climaciella brunnea (Say) shows a faintly impressed line on the 

 head as in Plega signata, but on boiling in water the line completely 

 disappears. 



Among the Planipennia the hemerobiid larva (fig. 10 I) resembles 

 the larvae of Corydalus, Chauliodes, and Raphidia in that the episto- 

 mal sulcus is incomplete and a Y-shaped line of ecdysis is present 

 with the arms going mesad of the anterior tentorial pits {at, at), 

 though they do not extend through the clypeal region. During ecdysis 

 of hemerobiid larvae, Killington (1936) says, "the thorax becomes 

 distended, and a split occurs dorsally along the thorax and extends 

 along the epicranial and frontal sutures of the head." 



In some of the other Planipennia, as Chrysopa, Myrmelcon, and 

 Ascalaphus, the larval head shows no trace of the coronal line 

 (fig. 10 H). Distally on the upper surface of the head, however, 

 is a triangular area set off by the arms of a V-shaped groove con- 

 taining the anterior tentorial pits (H, at, at). Sundermeier (1940) 

 calls this area the "labrum," but he gives no attention to muscle 

 attachments. In the Myrmeleon larva the cibarial muscles arise 

 anteriorly on the triangle, which fact, together with the articulation 

 of the mandibles on its lateral lobes, leaves no doubt that this area 

 beyond the V-shaped groove is in part the clypeus. Owing to the 

 immobility of the labrum, and the absence of a free hypopharynx, 

 there appear to be no labral or hypopharyngeal muscles to identify the 

 upper part of the triangle as the f rons, but it should be noted that the 

 head region above it is entirely occupied by the mandibular and 

 maxillary muscles. The area in question, therefore, must represent 

 the frontoclypeal region of Hemerobius (I) and of the Megaloptera, 

 together with the labrum, the frontal area being reduced because of 

 the absence of the usual frontal muscles. 



There is little evidence available as to the manner of ecdysis in 

 those Planipennia whose larvae have no apparent coronal line of 

 exuvial cleavage on the head. Smith (1922) says of the Chrysopidae 

 that at ecdysis the dorsal split of the thorax extends forward to the 

 head. Henriksen (1932), in reference to Smith's observation, notes 

 that if the cleavage line stops at the head, "this agrees with the fact 



