428 A7inals Entomological Society of America [Vol. VI, 



the vertex. The vertex or cranium (ec) comprises the dorsal 

 region in front of the occiput and bears the ocelli. This area 

 is not marked off from the frons (f), which lies above and 

 between the bases of the antennae (ant). The anterior margin 

 of the frons is united with the base of the clypeus or tylus (c). 



Below and on either side of the compound eyes (e) lie the 

 genae (g) while the ventral posterior portion of the head capsule 

 forms the basal plate or gula (gu). The clypeus, as has been 

 previously stated, is fused at its base with the frons, and at this 

 point is narrow, but as it curves forward and downward it widens 

 at its tip to form the base of attachment for the labrum (Ibr) 

 from which it is separated by a narrow membranous ring. 



The labrum is an elongate triangular sclerite. Its anterior 

 surface is convex, while its posterior surface is flat and contains 

 a groove which lies above the groove on the basal half of the 

 anterior surface of the labium (lab). 



On either side of the clypeus is a narrow prolongation of the 

 frons called the fulcrum, jugum or zygum (fr). The fulcra lie 

 close to the lateral walls of the clypeus, hiding them, but are not 

 united with them except at their bases, where they fuse with the 

 head capsule. The fulcrum is shorter than the clypeus, its 

 anterior margin lying behind the swelling of the tip of the 

 clypeus. Its ventral margin extends to the base of the antenna 

 where it fuses with the base of the maxillary laminae (ml) . 



The maxillary laminae or gena postica lie below the base of 

 the antennae. Their bases are fused with the genas and their 

 ventral . margins are united with the bucculee (bu) , which are 

 chitinous plates projecting from the anterior ventral side of the 

 head on either side of the base of the labium. The bucculce 

 serve to protect the posterior membranous portion of the base 

 of the labium. 



The rostrum, vagina or labium (lab) articulates with the 

 anterior ventral region of the head between the bucculas and is 

 made up of four segments, the terminal segment at its tip bear- 

 ing numerous sensory organs. The labium contains, as stated 

 above, a dorsal groove in which lie the setae (s). The edges of 

 the groove, distal to the overlying labrum, overlap, forming a 

 closed tube, thus giving the enclosed setae more support (PL 

 LVI, f. 8 s.). At its basal end the groove becomes very shallow; 

 the labium becomes filled with muscles, tracheas and nerves, 

 and the setae in this portion of the labium gradually come to lie 



