85 



August, 1907 {J. Bnind) ; R. Benue, between Amara and Ibi, 1008 

 (Dr. J. McF. Pollard, W.A.M.8.). Anglo-Egyptian Sudan: Blue 

 Nile, Senaar, September, 1902 {Major H. N. Dunn, R.A.M.C.). 



It may be worthy of note that the female from the vicinity of 

 Pawa, Northern Nigeria, was received with four specimens of Tahanus 

 tceniola. Pal. de Beauv. (Plate VIII., fig. 61), and a fifth Tahanus 

 too much damaged to be determinable, with the following general 

 label by the Acting Resident of Kano : " Wayam Fly : kills horses." 



Tahanus biguttatus, Wiedemann. 

 Aussereuropaische zweifliigelige Insekten, II., p. 623 (1830). 



Plate VI., figs. 44 (male) and 45 (female). 



This quite unmistakable fly is distributed from Cape Colony 

 to the Anglo-Egyptian Sudan and Abyssinia, and north-westwards 

 at least as far as the Lake Chad region of the French Sudan, Senegal, 

 and Southern Mauritania, while it also occurs to the east of the 

 Red Sea, in the Peninsula of Aden. In West Africa, as also in the 

 Anglo-Egjrptian Sudan or elsewhere, the typical race represented 

 in the figures may, at least in the case of the female, be locally 

 replaced or accompanied by one or other of certain forms, which differ 

 from it chiefly in the colour of the palpi and of the hair on the head 

 and back of the thorax. As wiU be seen from the figures, Tahanus 

 bigiUtatus exhibits a striking sexual dimorphism in the markings of 

 the body ; in the female sex, the hair clothing the head and back 

 of the thorax may be either golden-yellow (as in fig. 45), or whitish 

 yellow. Except for a fringe of whitish hair at the tip, the upper side 

 of the abdomen in the female is usually entirely dark, as shown in 

 the figure, but it occasionally happens that spots are present, similar 

 to those of the male. Thus, two females in the Museum collection, 

 from the Bahr-El-Ghazal, Anglo-Egyptian Sudan, and the 

 Hawash Valley, Abyssinia, have the abdomen spotted as in the 

 male, though in the case of the Abyssinian specimen the spots are 



