LAMB— DIPTERA : LONCH^ID^, SAPROMYZID^, EPHYDRIDiE, ETC. 



339 



OsciNis, Latreille. 



Oscinis Latreille, Hist. Nat. Ins. et Crust., xiv. (1804), p. 385. 



46. Oscinis dissimilicornis, n. sp. 



This species has different coloured antennae in the two sexes. This occurs also in 

 0. dimorpha Osten-Sacken as described in " Diptera from the Philippine Islands," Berlin. 

 Ent. Zeitschr., xxvi. (1882), p. 245. The present species differs in several respects; the 

 head is pale, the wings non-infuscate, the hind femora and tibiae are black instead of 

 brown, the size is about 1^ mm. instead of from 2^ to 3. They must be somewhat 

 related forms. 



$. Head. Frons yellow, dull ; the frontal triangle is duU greyish-black with a 

 broad base extending from eye to eye and a rounded front margin ; it extends to about 

 one-third of the distance from the vertex to the base of the antennae. Three pairs of fine 

 upper fronto-orbital bristles, outer orbital bristles short but stout and slightly converging 

 post-verticals, parallel upright ocellars one each side of the front ocellus. The rounded 

 front margin of the frontal triangle has small bristles, and the frons is also provided with 

 small bristles. Face whitish with small vibrissoe ; jowls pale yellow, a little less than 

 one-third the vertical height of the eye ; posterior eye-margins grey ; back of head 

 black. 



Eyes oval, microscopically ( x 16) pubescent. 



Antennae all yellow, arista black with slightly thickened basal joint, the rest being 

 very finely pubescent. 



Tongue black and chitinous. 



Palpi yellow. 



Thorax and scutellum dullish black with greyish yellow pollination and very short 

 bristly hairs on the dorsum of both ; the last dorso-central bristles present, two parallel 

 terminal scutellar bristles and two shorter side ones. Pleura same colour as thorax ; 

 metanotum shining black. 



Wings (Fig. 24) in no way infuscate, veins brown. 



Halters with a rather elongate whitish head and pale yellow stalk. 



Legs : front with yellow coxa;, infuscate femora, the rest yellow ; middle with 

 infuscate coxae and femora, the rest pale ; hind also with infuscate coxaj and femora, the 

 tibiae generally infuscate basally. 



Abdomen blackish, slightly shining and slightly paler at the base. 

 $ differs in that the second and third antennal joints are black. 



Size. 



if mm. 



Localities. Seychelles. Mahe: marsh just behind beach at Port Glaud, 5. XL 1908; 

 marshes on coastal plahi, Anse aux Pins and Anse Royale, I. 1909. 



