Vol. xxvii] 



ENTOMOLOGICAL NEWS. 



26l 



radial sector forks basally to the R-M cross-vein, or, in other words, 

 the small cross-vein is situated on the third longitudinal vein, instead 

 of on the praefurca; (2) the lower branch of the cubitus 

 is distinctly sinuous, the cell Cut having a convexity on the lower side 

 towards the base. The resemblance between the venation of Myceto- 



Fig. 2. Olbiogaster, venation. 



bia (fig. i) and Olbiogaster (fig. 2) is in some respects still more 

 marked, and it is worthy of particular notice that in Olbiogaster afri- 

 canus Edw., and still more conspicuously in O. sackcni Edw., the low- 

 est of the three veins arising from the discal cell (M 3 ) is less strongly 

 chitinized than the other two, suggesting that the venation of Mycetobia 

 has arisen directly from that of Olbiogaster through the obsolescence 



of Ms. 



In almost all other Mycetophilidae the radial sector, when it forks at 

 all, does so nearer the wing-apex than the position of the R-M cross- 

 vein, which, besides, is usually sloping, and not straight as it is in 

 Mycetobia. The only exception to this rule is the genus Pachyneura, 

 in which the radial sector forks exactly at the R-M cross-vein. In all 

 other Mycetophilidae, with the exception of Leiomyia (Glaphyroptcra) 

 and its allies, the cell GUI is concave instead of convex on its lower 

 margin. Ditomyia and Symmerus, genera which, together with Myce- 

 tobia, have been made to form the subfamily Mycetobiinae, agree in both 

 these respects with the other Mycetophilida-, and I therefore consider 

 that they are not at all closely related to Afycetobia. The genus Ms- 

 sochria, recently described from the Seychelles Islands, is, on the other 

 hand, closely related to Mycetobia. Its venation is very interesting, as 

 the media is evanescent; it evidently represents a further stage of evo- 

 lution from Mycetobia, in which the lowest branch of the originally 

 three-branched media has already disappeared. 



A comparison with other Diptera as regards the position of the 

 radial fork reveals the fact that in the Tipulid.-c, Culioidse, Psychodidae, 

 Orthorrhapha P.rachycera, and Cyclorrhapha, it always takes place 



