g4 THE EVOLUTION TIIEOKY 



with a rc.l.lisli yellow, or Muisli white hand— aiul quite constant. The 

 inuler surface, on the other liand, althouoh it always resembles a dead 

 leal", shows very varied i^round colours, being sometimes greyish, some- 

 times yellowish, or reddish yellow, or even greenish. Often it show^s the 

 lateral \ eining of the leaf quite as distinctly as in Fig. 13, but often 

 (luite indistinctly, and the black, mouldy spots [Sch) of our figure may 

 be more strongly marked, or they may be absent. It would seem as 

 if the mimicry of different kinds of leaves was here aimed at — so to 

 speak— just as in the case of the varied and numerous species of the 

 South American genus Aacm, wdiich usually live in the woods, and 

 are all more or less leaf-like, but each species is like a different leaf, 

 or like a leaf in a ditierent condition, dry, moist, or decomposing. It 

 is simply astounding to see this diversity of leaf mimicry, and the 

 extraordinary faithfulness with which the impression of the leaf 

 is reproduced. But it is by no means always the venation which 

 causes the resemblance, for this is often inconspicuous; the high 

 degree of deceptiveness is due to the silvery-clear ^^ellow, dark 

 yellow, red-brown to dark black-brown ground-colouring, which 

 is never quite uniform, and over which there usually spreads 

 a whitish ripple, combined wdth the remarkable imitation of the 

 sheen of many leaves. The upper side of this butterfly is almost 

 always conspicuously decorated with violet, dark blue or red, but 

 alwaj'S without any relation to the under surface. Not in all, but 

 in many of the species of this genus, we find the round, translucent 

 mirrors on the wing already mentioned in the case of KalUma, and 

 in some species quite remarkable means are made use of to make the 

 resemblance to a leaf thoroughly deceptive. Thus Anwa i^olyxo, 

 when sitting, looks like a leaf out of the edge of Avhich a caterpillar 

 has eaten a little piece ; in reality there is nothing missing from the 

 wing, but on the front margin of the anterior wing a semicircular 

 spot of a bright, soft, yellow colour stands out so sharply from the 

 rest of the chestnut-brown wing surface, that it has the effect 

 of a hole in the leaf. 



A modern opponent of the selection theory (Eimer) has suggested 

 that the marking of the lateral veins, and other resemblances to 

 a leaf in KalUma, represent nothing more than the pattern which 

 was present in any case, inherited from ancestors, and which in 

 the course of time arranged itself in a particular manner according 

 to internal developmental laws. Not selection — that is, adaptation 

 to surroundings — but the internal developmental impulse has brought 

 about the resemblance to the leaf. It is astonishing how^ a pre- 

 conceived idea can blind a man and weaken his judgment ! It goes 



