64 THE EEPOET OF THE No. 36 



Arising from the dorsal part of each lateral margin of the occipital foramen, 

 there is on each side a furrow or suture, more distinct than the epicranial suture, 

 which extends in a broad curve across the lateral aspect of the head to the cephalic 

 aspect, where it becomes obsolete (Figs. 1, 4, 5, and 27, vf). These are the vertical 

 furrows. They are not represented in lepidopterous larvge. They are also wanting 

 in the ScolioneuringB and Fenusinse and Phlebatrophia, which is a leaf-mining 

 phyllotomid. In Cephus the vertical furrows are distinct, but do not project be- 

 yond the cuticular fold of the prothorax. They are also present in Tremex, but 

 not so distinct as in Cephus. 



The dorsal, lateral, and the greater part of the cephalic and caudal aspects 

 of the head form a single area, the epicranium. This area is ordinarily subdivided 

 into three definite areas, the vertex, the front, and the genae, but in larvae and 

 generalized insects the number is greater. In some species these areas or sclerites 

 are surrounded by sutures ; in others a part of sutures are wanting. 



The shield-shaped area enclosed by the dorsal part of the arms of the 

 epicranial suture is the front (Figs. 1, 2, 3, and 9, f). There is not much varia- 

 tion in the size or shape of the front; the most marked is as to whether it is as 

 broad or broader than long. In ScoUoneura the stem of the epicranial suture is 

 only about one-half the length of the arms and the dorsal end of the front is an 

 acute angle. The surface of the front is usually similarly sculptured to the ad- 

 jacent parts. An exception is found in Cimhex, where it is roughened by irregular 

 anastomosing lines. 



The area on the dorsal aspect of the head included between the vertical fur- 

 rows is the vertex (Figs. 1, 2, and 4, v). It extends ventrad on each side of the 

 front to the ventral margin of the head and bears on its ventral portion the an- 

 tennae (Fig. 2, at) and the simple eyes or ocelli. The vertex is divided into two dis- 

 tinct pieces by the stem and arms of the epicranial suture. The front and vertex 

 are fused in Tremex through the obsolescence of the epicranial suture (Fig. 10). In 

 lepidopterous larvse there is a narrow plate, the adfrontal plate, formed by the 

 fusion of a part of the tentorium to the ental surface of the vertex along the epi- 

 cranial suture and extending as a narrow plate along each lateral margin of the 

 front like an inverted V. This plate is wanting in the Tenthredinoidea. 



The caudal portion of the head between the parts of the vertex on each side is 

 occupied for the most part by the genae (Figs. 1, 4 and 5, g). The genae can not 

 be considered other than as an area in these larvae: there are no sutures separating 

 it from the vertex. It is questionable whether it is ever more than an area of the 

 vertex. The portion of the head hetween the eyes and the ventral margin of the 

 head is usually designated as the genae. 



Between the genas of each side and the lateral margin of the occipital fora- 

 men, there is a distinct triangular sclerite in Pamphilius, the postgense (Figs. 4 

 and 5, pi). The apex of this triangle is located at the caudal end of a vertical 

 furrow and its base forms a part of the ventral boundary of the head. The suture 

 forming the lateral boundary of each postgena is not so distinct in Cimhex, and 

 each postgena, while triangular in outline, extends only to the middle of the 

 lateral aspect (Fig, 5). 



There is a transverse suture in PampliUhis extending on the dorsal part of the 

 caudal aspect of the head between the caudal ends of the vertical furrows, separat- 

 ing off a distinct sclerite, the occiput (Figs. 4 and 5, oc). This suture is subob- 

 solete at the middle of its course and the occiput is distinctly constructed at middle. 

 In Cim,hex this suture extends on each side to the dorsal end of a postgena and 



