(8) 



402 0. GORDON HEWITT. 



The epicranium (epicephalon of Lowne) on the posterior 

 surface of the head is flat. On the anterior surface it is 

 convex, and divided into a number of regions. On the top 

 of the head between the eyes it is called the vertex. This 

 contains the three ocelli situated on a slightly raised ocellar 

 triangle, which is surrounded by a second triangle, the 

 vertical triangle. The median region in front of and below 

 the vertex is the frons. In the middle of this there is a 

 black frontal stripe. In the male the eyes are only narrowly 

 separated by the frontal stripe. In the female the frontal 

 stripe widens out on the vertex. This character provides a 

 ready means of distinguishing the male from the female, as 

 the result of it is that in the male the eyes are close together 

 on the dorsal side being separated by about one fifth of the 

 width of the head, whereas in the female the space between 

 the eyes is about one third the width of the head. The 

 edges of the genes bordering on the frons bear each a row of 

 stout setae the fronto-orbital bristles. The antennae arise 

 from the lower edge of the frons. Each antennae consists of 

 three joints and the arista. The two proximal joints are 

 short and compose the " scape;" The third joint, the 

 flagellum, is longer, somewhat cylindrically prismatic in 

 shape, and hangs vertically in front of the clypeus. It is 

 covered with sensory setae, and contains two pits of sensory 

 function (olfactory, I believe). From the upper side the 

 plumose arista arises. This probably represents the terminal 

 three joints of the antenna. The lower edge of the frons 

 represents the anterior margin of the epicranium. 



The rest of the facial region is composed of the clypeus or, 

 as it is usually called, the face a convenient term, but one 

 which hides its true morphology. The face is depressed, 

 and is covered by the flagellae of the antennae. Between the 

 upper and lateral edges of the face and the lower edge of 

 the epicranium a crescentic opening, the lunule, marks the 

 imagination of the ptilinium. The epistomium is a narrow 

 strip below the face bounding the anterior edge of the 

 proboscis aperture. 



