4 Pysche [February 



head-capsule behind the eyes is well developed, the gula large, 

 the maxillary plates {a & h mxp) reduced and the mandibular 

 sutures (a. ms) short and end near the antennae. 



In the Coreids (Fig. 8) we find a similar arrangement, but the 

 inner edges of the frontal ridges do not meet together so closely 

 and do not cover the base of the antennae. The gular region is 

 elongated. 



In certain of the Pentatomids (Fig. 9) the clypeus (cl r) is 

 deflexed near its junction with the labrum, the frontal ridges 

 (fr) lie alongside of, but do not fuse with it. The clypeus thus 

 becomes dorsal, and the maxillary plates are thrown forward. 

 A similar arrangement takes place in the genus Coleotichus. 



The Reduviid head (Fig. 10) is the most difficult of all the 

 Hemiptera to homologize, on account of the distortion that has 

 taken place through its elongation, the ventral part having devel- 

 oped out of all proportion to the dorsal surface. 



In Pristhesancus (Fig. 10) it is impossible to recognize the 

 clypeal region from an external view, but upon dissection one 

 finds that the pharynx is attached to the head by its lateral struts 

 at a point slightly anterior to the base of the antennae (6. st), 

 and the pharyngeal muscles are attached to the medio-dorsal 

 surface behind these points. By homology with other Hemi- 

 pterous heads this must be the clypeal region (c. dr.). This form 

 of head could be brought about by two processes, firstly by amal- 

 gamation of the sides of the frontal ridges with the sides of the 

 clypeus in such a head as Figure 9, and the forward movement 

 of the lateral parts of the head, along with the elongation of the 

 gula; or, secondly, the frontal ridges could have moved forward 

 with the lateral and ventral parts of the head, and become abor- 

 tive, leaving the clypeus surrounded by and fused with the head- 

 capsule. In allied species there is a small prominence behind each 

 antenna which appears to be the remains of the frontal ridges, 

 thus indicating that the latter process is the more likely one. 

 The labrum and epipharynx (lb e), the maxillary plates (mxp) 

 and the mandibular sutures (ms) and the articulation of the 

 mandibular setse (art. man. s.) are normal and easily homologized 

 with other Hemipterous heads. The head behind the eyes is 

 greatly elongated. 



The nearest homology to the Hemipterous mouth parts is 



