African Species of the Ge7ius Acraea. 15 



extreme West, the extent of the red colour increasing as the 

 species ranges East and South, not only in the three species 

 mentioned, but to a less extent in 'pharsalus, which develops 

 into pharsalus pharsaloidcs. On the other hand this 

 change is in the opposite direction in A. li/coa, which, 

 beginning in the West as a pale semitransparent form, 

 gradually becomes more heavily and darkly pigmented 

 until it is represented at Mount Kilimandjaro by its sub- 

 species /«//oa'. A. penelope is a similar case in point. Two 

 of the black and yellow Acraeas, viz. orcas and servona, 

 exhibit a very marked change in the hind-wing under- 

 side colour in passing eastwards. Western examples are 

 lemon-ochreous beneath, the colour changing to brown, 

 or even nearly black, at Entebbe. A. servona retains 

 its pale yellow colour in German E. Africa, whilst A. 

 areas is of a slightly warmer tint in that locality. 



So extremely complicated is the variation of species 

 of the genus, that it has been more than once suggested 

 to me tliat hybrids are occasionally produced. I can only 

 say that after careful examination of over fifteen thousand 

 examples, I have seen no single individual which would 

 lend support to such a view. I have dissected out and 

 mounted the genital armatures of nearly five hundred 

 specimens, and have only once found an abnormal or 

 aborted example. So far as my observations enable me 

 to judge I should say that individual variation in these 

 organs is, except in one species, very slight and of rare 

 occurrence. I refer to A. acrita, as to the true taxo- 

 nomy of which, after examining hundreds of examples, I 

 am still in doubt. I am of opinion that each species can 

 always recognise a mate of its own kind, and it seems to 

 me that such infallibility may be not unconnected with 

 the production of some special exciting scent in one or 

 both sexes. 



With regard to the determination of species it may 

 be well to explain the general principles which I have 

 adopted in the present monograph. 



Without attempting to formulate a definition of the 

 meaning of the word species, I regard a species as a com- 

 munity of individuals, of which at least the geographic- 

 ally contiguous, and most probably, all the contemporary 

 members, are capable of, and, on the opportunity arising, 

 disposed to, syngamy. I am compelled to leave in doubt 

 the question of the syngamy of forms widely separated 



