IN DEFENSIVE COLORATION 321 



In the Somali Desert appears to be completely replaced, 

 by a form {dorippiis — klugii) without the black and white 

 tip to the wing (see pp. 70-1). Furthermore, in some 

 of the specimens the tawny colour is replaced by a tint 

 far more adapted for concealment against a sandy back- 

 ground. It is probable that under the stress of desert 

 conditions — constituting, as it were, a permanent dry 

 season — this highly distasteful form has been compelled 

 to adopt a measure of Cryptic Defence. Conversely, 

 in the luxuriant life and abundant food of the tropical 

 west coast of Africa, a form (the white-hind-winged 

 alcipptcs) even more conspicuous than the type, has 

 become dominant, and, from the mouths of the Niger to 

 the southern edge of the Sahara, is now apparently the 

 only form ^. 



"J, A. H. Thayer s Criticism of the Statement that 

 Animals are Conspiawtcs,— MT, Abbott H. Thayer has 

 criticized, from the artist's point of view, the use of the 

 term 'conspicuous' by the naturalist.^ In the first place 

 he states that ' Only tmshiny, bright ^ monochrome is intrin- 

 sically a revealing coloration. As soon as patterns begin, 

 obliteration of the wearer begins, . . . Nature does not 

 blunder, and Natural Selection would evolve the mono- 

 chrome, instead of a patterned surface, were simple con- 

 spicuousness her aim'. But naturalists, in using the 

 word 'conspicuous', have not meant to imply a con- 

 splcuousness as great as the artist could make it ; and 

 reasons have been given in the preceding Sections why 



* I should have carried the southern limit of the exclusive occurrence 

 of alcippus considerably further had I not recently seen in the Stockholm 

 Natural History Museum a male and a female specimen of the type form 

 captured respectively December 26 and 21, 1890, in the Cameroons, by 

 my friend Professor Yngve Sjostedt. They were, he told me, excessively 

 rare as compared with alcippus. In a large amount of material at Tring 

 and Oxford from far inland and considerably further south — Luebo, on a 

 southern branch of the Congo — the type form alone is represented. For 

 the suggested interpretation of the dorippus and alcippus forms, and for 

 the evidence that chrysippus is the ancestral form, consult Traiis. EnL 

 Soc, Lond., 1902, p. 473. 



^ Trans. Ent. Soc, Lojid., 1903, p. 556. 



^ Mr. Thayer tells me that he would now omit the words ^ unshiny, 

 bright '. 



POULTON 



