A STUDY OF MIMICRY 17 



tage which one species has over another will be 

 attacked by that other in every possible way ; 

 and if there be elements in the structure or mark- 

 ings which admit of a closer resemblance between 

 the two, and this resemblance will lessen the 

 disadvantage under which the weaker species 

 labors, then in the very nature of things that 

 resemblance must follow, unless other opposing 

 elements intervene. For here, at least, the rela- 

 tive abundance of the species concerned is an 

 essential element. It has been thought by some 

 to be also an essential element of all mimicry ; 

 but not only is there no sufficient reason for 

 holding such a view, excepting in cases like those 

 last quoted, but it has been asserted by no less 

 keen an observer than Fritz Miiller himself, and 

 agreed to by others, that the mimicked species 

 is not always more abundant than its counter- 

 feit ; indeed, the mimicking and the mimicked 

 species have been found to vary in their relative 

 nmnbers in different localities, sometimes the one, 

 sometimes the other, preponderating. But with 

 regard to mimicry of one distasteful butterfly by 

 another, there may also enter another element ; 

 for it is hardly to be believed that all distasteful 

 butterflies are equally objectionable to all birds, 



