A STUDY OF MIMICRY 9 



blance of a band there, — liow small soever this 

 difference may be, it must, by the very laws of 

 natural selection, be cherished, perpetuated, in- 

 creased, by slow but sure steps. Nor is there any 

 limit to its increase except its absolute deception 

 of the enemy. So long as there is the slightest 

 advantage in variation in a definite possiI)le direc- 

 tion, the struggle for existence will compel that 

 variation. Knowing what we now know of the laws 

 of life, mimicry of favored races might even have 

 been predicted. 



It is to be presumed that the actual colors found 

 in a mimicking butterfly are, with rare exceptions, 

 such as existed somewhere in the ancestral form. 

 In the case of our own mimicking Basilarchia, for 

 example, whose orange ground tint is so totally at 

 variance with the general color of the other nor- 

 mal members of the group, it will be observed that 

 aU the normal species possess some orange. With- 

 out this as a precedent fact, such perfect mimicry 

 might perhaps never have arisen. Individuals 

 among the normal species vary somewhat in this 

 particular, so that it is easy to suppose that some 

 of the original B. archippus, with more orange 

 than usual, may have escaped capture, on occasion, 

 from this cause. From such a small beginning, 



