340 PERCY SLADEN TRUST EXPEDITION 



47. Oscinis acuticornis, n. sp. 



This is the smallest species ; it is entirely more or less shining black except for its 

 paler legs and yellow halters, and can be at once recognised from its small size and the 

 pointed tip to the large third antennal joint. 



Head (PI. 16, fig. ll). The frontal triangle is shiny black and practically covers the 

 whole frons from the vertex to the rounded front margin just above the antennae, leaving 

 only the eye-margins free. The face is deeply pitted between the eyes and below the 

 lunula, and the antennae are partly sunk in this pit. Below the pit the face is seen to 

 project when viewed in profile. Antennte black with a large hairy third joint ending in 

 a small spike which is 2Dartly formed by a terminal thorn ; arista blackish, stout and 

 pubescent ( x 45), second joint with a hair. Eyes microscopically pubescent. 



The specimens are not in good condition but it is possible to see a fine fronto-orbital 

 row of bristles, crossed post-verticals and upright ocellars. Jowls about one-sixth of the 

 height of the eye. 



Thorax sparsely clothed with fine bristles, the last pair of dorso-centrals present. 

 Scutellum slightly brassy with a rounded tip and two terminal bristles. 



Wings (Fig. 25), veins dark brown. 



Halters pale yellow. 



Legs pale brown with darker femora. 



Fig. 25. Oscinis acuticwnis, n. sp., wing. 



Abdomen duller black than thorax. 

 Size about f mm. 



Locality. Seychelles. Mahe : marshy ground near sea-level at Cascade, 20. II. 

 1909. 



The following four s^^ecies form a group of very similar species which are allied to 

 0. atricornis Zett., and differ from the normal forms of the genus in their more slender 

 shape. They are shining black in colour and with wings whose length is in general 

 unusually great relative to the body length. They are somewhat variable in colour of 

 the legs and in the relative breadth and length of the wings. This is noticeably the case 

 in the first species (0. oculata) in which specimens occur which are exactly similar in all 

 the important characters except that the wings (in the extreme cases) may vary between 

 the forms given in Figs. 26 and 27. It is possible that further knowledge of the habits 

 and food plants may enable the species to be more accurately subdivided. 



48. Oscinis oculata, n. sp. 



$, ?. Head (PL 16, figs. 12, 13). Frons black with a large shining frontal triangle 

 (fig. 20), the base occupies very nearly the full space from eye to eye at the vertex, the 



