DARWIN AND BERGSON ON EVOLUTION 



specimens from the tropical west coast of Africa, a little north of 

 the Equator ; the right-hand column (Figs. 5 — 8) a series from the 

 neighbourhood of Entebbe, on the Equator, at the north-west 

 corner of the Victoria Nyanza. 



The upper surface of the wings of all these butterflies, as well as 

 of those shown in Figs. 9 — 14, is of a dusky, almost a black, ground- 

 colour, with a pattern of white, ochre (restricted to Figs. 4 and 8), 

 fulvous, or partly white and partly fulvous. This latter tint, very 

 common in butterflies, is somewhat difficult to describe. Abbott H. 

 Thayer, the American artist-naturalist, meets the difficulty by calling 

 it " cow-red." Perhaps " orange-brown " conveys a sufficiently 

 correct idea of its deeper, " orange-ochre " of its paler shades. The 

 dusky and white are so well reproduced that coloured figures would 

 not give a much better idea of the appearance. The ochre, and the 

 fulvous tints are clearly indicated by the depth of the shade, although 

 here colour would, of course, be a great improvement. 



Fig. 1 represents the female, Fig. 2 the male of Planema alcinoe, 

 belonging to the distasteful, much-mimicked family of the Acrceince, 

 and itself proved by Mr. W. A. Lamborn to be highly unpalatable 

 to monkeys which devoured many other butterflies with avidity, 

 and to an insectivorous lizard, Agama colonorum, common in the 

 locality. Fig. 3 represents the female, and Fig. 4 the male of the 

 common Acrcea alciope. The figures clearly indicate the fact that 

 the female differs from the male in the substitution of fulvous for 

 ochre, and in the form of the pattern. She is also distinguished by 

 her greater size, but here the effect is exaggerated because the male 

 is a dwarfed specimen. The result of these differences is that the 

 female Acrcea (Fig. 3) is an excellent Mimic of the male Planema 

 alcinoe (Fig. 2), a butterfly larger than itself. There is little doubt 

 that other fulvous-marked western Planemce with patterns — in some 

 species female as well as male— very similar to that of the male 

 alcinoe, combine with this latter in supplying Models for the female 

 A. alciope. But the details of the pattern, as well as the facts of 

 geographical distribution, indicate that the male PI. alcinoe is the 

 principal Model. Although it is rather unusual in butterflies for 

 a male to be mimicked by a female, the same exceptional relation- 

 ship holds in the eastern part of the range of alciope, where another 

 mimetic female mimics another male Planema (see p. 61). 



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