204 Annals Entomological Society of America [Vol. XIII, 



vestiture of the occiput shows more or less distinct regions of 

 which one is very clearly defined. This is a region just back 

 of the compound eyes, the posterior eye orbit, set off from the 

 rest by a row of more prominent hairs (Figs. 3, 4 and 7). There 

 is a small patch of fine bristles at the base of each epioccipital 

 sclerite, while the epicephalon is bare, except for the post ver- 

 tical bristles. The metacephalon is divided into two lateral 

 regions by the vestiture, leaving a groove in the center prac- 

 tically bare. 



Viewing the head from the front (Figs. 1 and 2) the most 

 striking difference between the sexes is in the compound eyes. 

 Those of the male are very large, being practically contiguous 

 for a short distance, while in the female they are smaller and 

 widely separated. The antennae of the female are located higher 

 up than are those of the male, and the vertical bristles are much 

 larger. Except for a considerable narrowing in the male the 

 regions in both sexes are homologous. The male head bears 

 more bristles than the female but they are weaker and less 

 prominent. 



At the extreme vertex of the head in both sexes there is a 

 heavily chitinized, slightly raised, almost equilateral triangle, 

 with its apex directed towards the base of the antennae. This 

 is the ocellar triangle (ot) and it bears a simple eye in each 

 corner. It bears three or four pairs of stout short bristles, 

 the posterior ones upright, and the anterior ones directed for- 

 ward. Below the ocellar triangle and above the base of the 

 antennae is a region known as the front. In the males this is a 

 triangle with the apex directed upward and is known as the 

 frontal triangle (ft.) (Fig. 2). In the females the front (f) is 

 broad, somewhat rectangular, bears a pair of bristles located 

 just below the ocellar triangle, and directed forward, the 

 cruciate bristles. In the male these two bristles are located 

 very close together at the apex of the frontal triangle. 



The vertex in the female bears two pairs of large vertical 

 cephalic bristles, the inner pair convergent and the outer pair 

 divergent. Behind the ocellar triangle is a pair of divergent 

 post vertical bristles. 



On each side of the front, bordering the compound eyes, is a 

 narrow region which reaches from the vertex to the base of the 

 antennae, where it is cut off by an oblique division line. These 

 two areas are the parafrontal plates (prf) bearing eight pairs of 



