THROUGH THE YEAR 55 



tion, chief agent of evolution. The truth of these 

 great theories is irresistibly borne in on me. But 

 not everything means natural selection or sexual 

 selection. Nature does not keep arming a butterfly 

 or a bird against foes which never or rarely 

 threaten it. 



So much for butterflies at home. Turning to 

 foreign butterflies, there does seem a very strong 

 array of facts pointing to protection by colour, mark 

 and form. Two families kallima and ancea 

 appear to mimic dead leaves exactly. Kallima 

 we often see in collections but ancea is perhaps a still 

 better mimic. With its wings folded, it shows 

 stalk, ribs, apex. Here is something like a sham ! 

 Ancea divina has a light circular mark at the edge 

 of its folded wings that looks like a bit of a leaf 

 eaten by a caterpillar. The idea of a butterfly copy- 

 ing a leaf that has been bitten by a caterpillar is 

 quaint, a sly touch in Nature. Better, there is an 

 African butterfly Papilio dardanus whose female 

 mimics a certain butterfly said to be distasteful to 

 birds, but whose male, for the same purpose, mimics 

 quite a diff erent butterfly. It would not do for too 

 many threatened butterflies to mimic one kind of 

 unthreatened butterfly : the birds would " jump 

 to it," suggests Professor Weismann. 



As to the tiny light-coloured mark on the under- 

 side of the comma's wings, may it not be kindred 

 with the rings and dots printed on the undersides 

 of butterflies' wings ? There is the painted lady, 

 for example. Her undersides have several rings. 



