PROTECTIVE PIGMENTS AND APPEARANCES 35 



What is perhaps the most remarkable resemblance between an 

 animal and a part of its surroundings is furnished by the East India 

 butterfly Kallima (Fig. 172). The undersurface of the wings, exposed 

 when this butterfly is at rest, resembles a brown leaf with a distinct 

 midrib and veins passing from this 

 to the edges. Near one end is a dark 

 spot close to a nearly transparent area, 

 resembling very much the kind of spot 

 often produced by the action of some 

 fungus. The details are very sharply 

 defined and almost uniform. If one 

 of us should see a flying kallima come 

 to rest on a twig, he should perhaps 

 have some difficulty in distinguishing 

 the insect among the leaves ; it is pos- 

 sible also that the lizards and birds 

 that feed upon this species are some- 

 times baflfled in their pursuit of prey. 

 Yet it is doubtful (i) whether the ad- 

 vantage of this resemblance has had 

 anything to do with its gradual appear- 

 ance as a character of this species, and 

 (2) whether, indeed, it is an advantage 

 (see Fig. 171). 



Fig. 172. The Indian leaf butter- 

 fly (Art///z«a). (Slightly reduced) 



Many arguments concerning the evo- 

 lution of animal life have been based 

 on the striking resemblance between 

 the wings of this insect when at rest 

 and brown leaves. It has been said 

 that the animal looks like a leaf only 

 when it comes to rest with the head 

 up ; but observers who have seen the 

 animal in its native surroundings tell 

 us that it always comes to rest head 

 dow7i, on guard against lizards. In 

 this position it is sufficiently con- 

 spicuous to be recognized even by 

 untrained human eves 



403. Warning colors. We saw 



that some of the wastes produced 

 in Hving bodies are poisonous (see 

 p. 203), and we can understand that 

 the presence of these poisons in the 

 body of a plant or an animalHvould 

 make such a body undesirable as 



food for another animal. Distasteful (bitter, sour, acrid, foul- 

 smelling) substances may thus serve to protect organisms 

 against possible enemies. Poisonous and distasteful substances 

 in an animal body are often associated with conspicuous colors, 

 which have been called warning colors by some naturalists. 

 The idea is that the bright color warns enemies against eating 



