DOLICHOPIDJE. 145 



Ala lofjo axillari ohsokto, vena costali circa apicem alae abrupta, 

 cubitcdi simplici ; areolis prcebracldali et anali minatisaimis, poliracliiali 

 c/fusa in discalem elonyatam, vnta transversa simplici clausam. Abdomen 

 si'tj mentis 5 (aut pluribus in mare). 



The Dolichopidte are in general small flies, rarely exceeding 

 three lines in length ; distinguished by the prevalence of metallic 

 tints, with a partial coating of tomentum, repelling water, which 

 communicates a hoary gloss particularly to the lower parts ; this 

 is composed of excessively minute, short, compressed, pellucid 

 hairs, laid flat, and often so thickly set as to overlap in several 

 layers. The head is nearly as broad as the thorax, usually repre- 

 senting a segment less than a hemisphere ; the occiput flat and 

 vertical, its orbit towards the vertex with a row of bristles 

 (" supercilia," Bouche), another row, often of a different colour, 

 or else a beard of soft hair, along the lower orbit. The eyes 

 mostly pubescent, large, occupying the sides of the head entirely, 

 so as to form part of the peristoma, scarcely ever leaving a narrow 

 line of cheek between. On the front they are distant, except in 

 the males of the genus Diaphorus. The vertex is usually more or 

 less sunk between the eyes, leaving a prominent tubercle, which 

 bears the three ocelli in a triangle guarded by long bristles. The 

 face is not expanded into cheeks below; the lower region not 

 inflected to the peristoma, but separated from the upper by an 

 elevated line or by a tubercle at each side. Sometimes, especially 

 in the males, the face becomes extremely narrow, or the eyes meet 

 below the antennae. There are no vibrissae. The cavity of the 

 mouth is nearly round, filled by the proboscis, which is directed 

 downwards, in general projecting little, but larger in the female 

 than the male, not forming a visible angle with the short retracted 

 mentum. The palpi of one piece, broad, compressed, inserted on 

 the base of the proboscis, meeting in front, and incumbent on it, 

 like a bilobed epistoma. The labrum is unusually stout, and 

 its deflected sides are furnished with one or two sharp teeth; 

 these are separated by deep incisions, but are not free, as has been 

 represented (Hal. z. j. v. 35 i), nor does there seem to be ground 

 for considering them as representing the maxillae (LI. gen. iv. 290). 

 The tongue, which is abruptly enlarged at the base, is by this 

 means prevented from fitting closely into the groove of the labrum, 

 and lies lower down between the toothed edges of it. There is no 

 trace of maxilla. The genera Orthochile and Aphrosylus present 

 modifications of this structure, noticed in their proper places. The 

 antenna are extended forwards, usually shorter than the head, 

 VOL. i. u 



