the Butterflies of the White Nile. 51 
There are many species of Pierinae, and several 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 8. Sidan, 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 Sadan, alike on the Red Sea coast and on 
the White Nile, from Khartim right up to Rejaf, the 
beautiful, but puzzling genus Teracolus is dominant. 
The most abundant and generally distributed species 
are 7’. evarne and T’. eupompe, but several others—T. daira, 
T. evagore, T. phisadia, T. halimede and T. protomedia, 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 8. 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. 
