CREATION BY EVOLUTION 



conspicuous. But as the naturalist passes from one district to 

 another he sees that the pattern of the groups becomes dif- 

 ferent, "as if at the touch of an enchanter's wand," to use the 

 words by which Bates describes the change that sweeps over 

 all the diverse members of a group. In Central America and 

 Venezuela the chief group is made conspicuous by a tawny 

 and black-barred pattern; in the Guianas the members of the 

 corresponding group have much darker hind wings — the 

 wings of some are almost entirely black; across the Amazon, 

 in eastern Brazil, the hind wings change in the opposite direc- 

 tion, gaining a bright yellow stripe; high up the Amazon, at 

 Ega (now Teffe), Bates' headquarters for many years, the 

 general colour of both wings changes from tawny to deep 

 chestnut. 



How shall we explain the advantages of these local colours 

 and patterns, which run through many distantly related spe- 

 cies? Let us see. 



The insect-eating animals of each district, especially the 

 birds, learn by experience that insects having certain con- 

 spicuous colours and patterns have an unpleasant taste or 

 smell or are indigestible. So if a number of different 

 noxious species bear the same pattern the birds easily learn 

 to avoid them, with little waste of insect life in experimental 

 tasting. Those so marked survive. Hence the great advan- 

 tage to the butterflies of a combined advertisement or 

 announcement that they are unpalatable, instead of each dis- 

 tasteful species having its own warning pattern, requiring 

 to be tested separately. It is probable, too, that among the 

 members of a large group there are many degrees of dis- 

 tastefulness and some also that are not distasteful at all, but 

 that flaunt a false advertisement and live on the reputation 

 (or rather the disreputation) of the others. This false adver- 

 tisement was interpreted by H. W. Bates and is spoken of as 



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