TABANUS FROM THE ANGLO-EGYPTIAN SUDAN. 177 



latter, rather than a distinct species. While this is certainly possible, it seems 

 for the present advisable — until the question can be definitely decided by the 

 examination of further material belonging to both sexes — to concede specific 

 rather than merely varietal rank to T. viordax. Although on a cursory examina- 

 tion Tahanus mordax may easily be mistaken for T. leucostomus, since, in the 

 female sex at any rate, the abdominal markings in the two cases are identical, 

 the former may be distinguished from the latter by the great development of the 

 supra-antennal protuberance, and by the absence of an appendix to the anterior 

 branch of the third lona-itudinal vein. 



