302 THERE VII^E. 



tinged with brown along the borders of the veins; poisers tawny, 

 their knobs black, with a hoary tinge. 



" Length of the body 3±- lines, of the wings 5 lines. East India." 

 (Walker.) 



240. Thereva invaria, Walk. 



Thereva invaria, Walker, Ins. Saund., Dipt. pt. 3, p. 159 (1852). 

 2 . " Body black, clothed with black hairs ; head clothed 

 beneath with white hairs ; sucker pitchy, clothed with tawny 

 hairs ; breast and underside of abdomen grey, the former partly 

 clothed with whitish hairs; abdomen spinclle-sbaped, very much 

 longer than the chest ; hind borders of the segments lurid • a laro-e 

 tuft of white hairs on each side of the base ; legs black, clothed 

 with short black hairs, beset with a few black bristles ; foot- 

 cushions pitchy; wings slightly grey; wing-ribs pitchy; veins 

 black, strongly marked, pitchy towards the base ; brands brown ; 

 poisers pitchy. 



" Length of the body 5 lines, of the wings 9 lines. East India " 

 (Walker.) 



Genus PSILOCEPHALA, Zett. 



Psilocephala, Zetterstedt, Ins. Lapp. p. 525, note (1838) ; id., Dipt. 

 Scand. i, p. 19 (1838) (Psilocehala, lapsus). 



Genotype, Bibio imberbis, Jin. (Sweden) ; by Coquillett's 

 designation (1910).* 



This genus differs from Thereva in the bare face ; and from a 

 nearly allied European genus, Dialineura, which may probably 

 occur in India, it is known by the 1st antennal joint beinc no 

 broader than the 2nd and not more bristly than usual. The 

 alleged character that the 1st joint is shorter than the 2nd and 

 3rd combined, as compared with its being longer than the 2nd and 

 3rd together in Dialineura, seems an uncertain one. 



The species are by no means almost bare, as stated by Verrall. 



Range. Europe, Asia, North, Central, and South America, 

 North and South Africa, Madagascar, Sokotra. 



Life-history. Probably similar to that of Thereva. 



Five species are definitely known from India or Ceylon, with 

 one additional species, sequens, Walk., requiring confirmation. 

 These five are difficult to tabulate, from the general similarity of 

 the descriptions, although when placed side by side the species 

 may appear quite distinct. The colour of the legs, though 

 apparently an unreliable character, is perhaps as constant a one 

 as any, but the present table is, at best, only a preliminary one.f 



* It would have been better to have selected the well-known European 

 ardca, F., as genotype. 



t It is advisable in this family to compile a separate table for each sex, but 

 the females are known of only three out of the five species. 



