244 Mr. H. Mace on Butterflies on the Nile. 



Mr. Whitfeild's theory is that these new species have 

 been brought down the river among the fodder which is 

 constantly being imported. Khartomn is steadily develop- 

 ing and importations of this kind continually increase. 

 He thinks that large numbers of insects in all stages come 

 down the river in this way, and that the increasing area 

 of cultivation makes it possible for many to establish 

 themselves. 



It seems a very reasonable conclusion, and is certainly 

 supported by the general distribution of the insects as 

 shown in the above table. Only 19 of the 75 species are 

 found outside the Ethiopian Region, and of these only 

 eight extend into the Palaearctic Region. Of these it 

 may be said that about half are generally considered 

 Ethiopian types and the other half Palaearctic, but in 

 face of the distribution shown by the table, one is led to 

 believe that the greater probability is that all of them 

 originated in Africa and passed down the Nile Valley 

 into the Palaearctic Region. Certainly not more than 

 eight or ten of the whole number can be regarded as 

 Palaearctic forms which have gone south, and it seems 

 to me that the semi-artificial introduction which has 

 taken place during the last few years is only an extension 

 of the natural process by which species have been carried 

 down the Nile and established at favourable points. 



