43 ^ELEMENTARY ZOOLOGY 



with purplish and orange markings not at all resembling 

 a dead leaf. But the butterflies when at rest hold their 

 wings together over the back, so that only the under sides 

 of them are exposed. These are exactly the color of a 

 dry dead leaf with markings mimicking midrib and 

 oblique veins, and, most remarkable of all, what are 

 apparently two holes like those made in leaves by insects, 

 but in the butterfly imitated by two small circular spots 

 free from scales and hence clear and transparent. When 

 Kallima alights it holds the wings in such position that the 

 combination of all four produces with remarkable fidelity 

 the simulation of a dead leaf still attached to the twig by 

 a short pedicel or leaf-stalk (imitated by a short ' ' tail 

 on the hind wings). The head and legs of the butterfly 

 are concealed beneath the wings. 



Warning colors, terrifying appearances, and mimicry. 

 While many animals are so colored as to harmonize 

 with their habitual or usual environment, others on the 

 contrary are very brightly colored and marked in such 

 bizarre and striking pattern as to be conspicuous. There 

 is no attempt at concealment; it is obvious that conspicu- 

 ousness is the object sought or at least produced by the 

 coloration. Animals like these, we shall find, are in 

 almost all cases specially protected by special weapons of 

 defence such as stings or poison-fangs, or by the secretion 

 of an acrid, ill-tasting fluid in the body. Many cater- 

 pillars have been found, by observation in nature and by 

 experiment, to be distasteful to insectivorous birds. Now 

 it is obvious that it would be advantageous to these cater- 

 pillars to be readily recognized by birds. After a few 

 trials the bird learns by experience to let these distasteful 

 larvae alone ; their conspicuous markings serve as warning 

 colors. The black-and-yel low-banded caterpillar of the 

 common milkweed or monarch butterfly (A nosia plexip- 

 ) is a good example of such protection by a combina- 



