the Butterflies of the White Nile. 51 



There are many species of Pierinae, and severa of 

 these are abundant, or at least common, so that when 

 individuals are taken into consideration this group by 

 far outnumbers all the others put together. 



In the S. Sudan, as everywhere, there are some favoured 

 spots where butterflies are found in unusual numbers. 

 One may spend an hour in such a spot among clouds of 

 " Whites " and " Yellows " without catching sight of a 

 Swallow-tail, a Nymphalid or a Skipper. 



The impression left on the mind is that throughout the 

 Anglo-Egyptian Sudan, alike on the Red Sea coast and on 

 the White Nile, from Khartum right up to Rejaf, the 

 beautiful, but puzzling genus Teracohis is dominant. 



The most abundant and generally distributed species 

 are T. evarne and T. eupompe, but several others — T. daira, 

 T. evagore, T. phisadia, T. halimede and T. profomedia, are 

 common enough where they occur, and it is indeed a 

 beautiful and a bewildering sight to see these " orange- 

 tips " and " crimson- tips," with here and there a " purple- 

 tip " flying over the dead grass or the flowering shrubs. 



That the Butterfly Fauna of the White Nile has a de- 

 cidedly desert character was noticed long ago by Butler 

 (9. p. 25) and by Dixey (12. p. 142). This is made very 

 clear by a comparison with the fauna of S. Arabia, brought 

 to our knowledge mainly by the labours of Col. Yerbury 

 in Aden and its neighbourhood. 



A glance at the preceding table shows that, as might 

 have been expected, the South Arabian Fauna is even 

 poorer than that of the White Nile, but — with the notable 

 exception of the total absence of the great genus Acraea — 

 the distribution between the families is very similar. It 

 is very remarkable that out of the Arabian total of fifty 

 species, no less than thirty-eight are found on the White 

 Nile.* 



Although Yerbury's operations were confined to a com- 

 paratively small area it may be assumed that his list is 

 nearly complete, whereas mine is very far from such 

 perfection. Collectors with more time at their disposal 



* It is not possible when comparing lists to be certain that 

 different authors mean the same things by the same names. But 

 this difficulty has been minimised by the fact that neither Dr. 

 Dixey nor Col. Yerbury are "splitters." My conclusions are 

 mainly, though not entirely, founded upon the great Hope Collec- 

 tion, in which the Pierinae have been so admirably arranged by 

 Dr. Dixey. 



