1915] on Mimicry and Butterflies ;373 



resemblances between conspicuous species belonging to different 

 groups. Such resemblances between the models themselves also 

 strongly attracted the attention of Fritz Miiller, a great German 

 naturalist resident in Brazil - so strongly indeed as to prevent him 

 from accepting Bates' hypothesis as an explanation of wide applica- 

 tion among butterflies. The great majority of the superficial like- 

 nesses between his Brazilian butterflies belonging to different groups 

 were clearly not to be interpreted by the mimicry of Bates, for of 

 this majority all were abundant, conspicuous, slow-flying, and 

 presumably protected by taste, smell, or some special quality which 

 rendered them unpleasant or unwholesome as food. Bates had 

 suggested that such a likeness between models was due to some 

 influence, presumably physical or chemical, connected with locality ; 

 but this interpretation did not satisfy Fritz Miiller. For many 

 years he puzzled over the subject, testing various ideas, as, for 

 instance, the possible operation of sexual selection, throwing out 

 the suggestion in his correspondence with Charles Darwin, that 

 butterflies in the choice of their mates were influenced by the appear- 

 ance of other butterflies in the same locality. Concerning this bold 

 hypothesis, Darwin wrote, January 23, 1872, to Prof. Meldola : 



" You will also see in this letter a strange speculation, w^hich I 

 should not dare to publish, about the appreciation of certain colours 

 being developed in those species which frequently behold other forms 

 similarly ornamented. I do not feel at all sure that this view is as 

 incredible as it may at first appear. Similar ideas have passed 

 through my mind when considering the dull colours of all the 

 organisms which inhabit dull-coloured regions, such as Patagonia and 

 the Galapagos Islands." 



It was, however, impossible to accept sexual selection as a valid 

 explanation of the facts, because in a large proportion of mimicking* 

 species the resemblance was confined to the female. On the other 

 hand, there were hardly any species in which the male but not the 

 female was a mimic. At the same time many facts disproved Bates' 

 suggestion that physical or chemical forces were responsil)le for the 

 likeness between models. Finally, in 1878,* sixteen years after the 

 publication of Bates' memoir, Fritz Miiller hit upon an explanation 

 with which he was satisfied. The idea evidently came to him quite 

 suddenly, for he begins his first little paper on the subject : '' It is 

 remarkable how one sometimes puzzles for years over questions the 

 solution of which is so simple, that one can hardly understand how 

 there could have been even a momentary difficulty over them." 



Fritz Mliller's interpretation of what has since been known as 

 "Miillerian Mimicry," depends on the saving of life during the edu- 

 cation of insect enemies. When two warning patterns are different, 

 they must be learned and remembered separately, and the two species 



* Zool. Anzeiger (Carus), i. (1878), pp. 54, 55. 



