NO. 13 STAPH YLINIDAE BLACKWELDER II 



or epicranial suture). The term gena is used to designate the area 

 (fig. I E, ge) on the lateral aspect of the head between the eye and 

 the dorsal articulation of the mandible. It is not set ofif as a separate 

 sclerite. The frons is present as an area in all insects to be defined 

 by the frontal sutures and the epistomal suture, if present, but bear- 

 ing the origin of the labral retractor muscles. In the present species 

 neither the frontal nor the epistomal sutures are present, and the 

 frons is therefore represented only in a triangular area behind the 

 line of the anterior tentorial pits. 



The clypeus is divided into two distinct sclerites, the postclypeus 

 (fig. I A, E, pclp) and the anteclypeus {aclp). The postclypeus is 

 fused with the frons at the line of the anterior tentorial pits and 

 extends around the antennal fossae. The anteclypeus is a membranous 

 strip between the anterior margin of the postclypeus and the labrum 

 (/m). 



The labrum (fig. i G, H) is a broad bilobed sclerite attached to the 

 cephalic end of the clypeus. It is continuous with the rest of the dorsal 

 surface of the head. Its anterior dorsal margin is clothed with both 

 stout and fine setae, whereas the remainder of its dorsal surface is 

 smooth and less heavily sclerotized. The ventral surface is covered 

 with very fine recumbent hairs, with two large areas of cross-hatched 

 ridges. The ventroposterior projections of the labrum are the tormae 

 (tor) and carry the insertion of the retractor muscles of the labrum. 



Lying between and posterior to the tormae and caudad of the ven- 

 tral surface of the labrum is an H -shaped sclerite (fig. i G, H) which 

 appears to articulate with the inner faces of the tormae. Its posterior 

 arms taper regularly to a stubby point, from which arise a cluster of 

 very fine fibers or hairs. This sclerite is apparently united by mem- 

 brane to the tormae. 



The epipharynx is apparently not present as even a definite area 

 unless possibly it is represented by the two ribbed areas on the ventral 

 surface of the labrum (fig. i H). 



The ventral aspect of the head (fig. i A) is occupied by three 

 sclerites or regions. These are a median and two lateral areas. The 

 first is the gula (gu), a narrow longitudinal sclerite with an expansion 

 at the posterior end. The lateral areas are the ventral prolongations 

 of the caudolateral parts of the epicranium. These represent the post- 

 genae and the subocular parts of the vertex as described above. 



The gula (fig. i A, gii) is believed to be a sclerotization of the neck 

 membrane posterior to the submentum and the tentorial pits and be- 

 tween the ventral extensions of the postocciput. The cephalic migra- 

 tion of the tentorial pits from the foramen magnum has extended the 



