86 



THE EVOLUTION THEORY 



down so artistically that the ' upward turning leaf-stalk is in juxta- 

 position to a twig,' we may answer that a bird flying fast is not 

 likely to look to see whether every leaf in the profusion of foliage 

 in the primitive forests is properly fastened to its stalk or not, any 

 more than we should do in the case of a painted bush, on which many 

 a leaf has the appearance of floating in the air, just as in nature, or in 

 its faithful copy, the photograph. 



Quite different from the leaf-marking either of Goenophlehia 

 or Kallima is that of one of the Satyrides of the lower Amazon 

 valley, Goarois chorinceus (Fig. 15). If one spreads this butterfly 



out in the usual 

 V way it does not 



look in the least 

 like a leaf, and one 

 only sees a number 

 of curiously placed 

 disconnected stripes 

 on the under sur- 

 face of the wing. 

 But if the wings 

 be folded together 

 to correspond with 

 the sitting position 

 of the butterfly, 

 there appears the 

 figure of a leaf, 

 of which, however, 

 only half is present, 

 and whose midrib 

 (inr) runs obliquely 

 forward from the 

 inner angle of the 

 posterior wing. Here, again, it is not. difficult to guess that this 

 straight stripe has arisen, by displacement and straightening, from 

 a curved line inherited from some remote ancestor, and it is these 

 precise changes which are the work of the adaptive processes of 

 natural selection. The same applies to the lateral ribs (sr), which are 

 here four in number. 



But even the division of the wing surface by a single dark line, 

 such as that which crosses the middle of the posterior wing of 

 Hebovioja (Fig. 9), an Indian butterfly, heightens not inconsiderably 

 the resemblance of the resting butterfly to a leaf, a resemblance which 



Fig. 15. Ccsrois chorinceus, from the lower Amazon, in its 

 resting attitude. F, anterior wing. B, posterior wing, mr 

 midrib of the apparent leaf, sr, lateral veins. sL hint of 

 a leaf-stalk. 



