406 EVOLUTION AND ANIMAL LIFE 



it to capture its prey. They are uses obviously concerned 

 with the "struggle for existence": they are "shifts for a living." 

 For the sake of clearness in discussion these various uses 

 will be rather arbitrarily classified into several categories which 

 in Nature are not so sharply distinguished as the paragraph 

 treatment of them might suggest. 



The general harmonizing in color and pattern with the color 

 scheme of the usual environment is a condition which every 

 field student of animals recognizes as widely existing. The 

 green color of foliage-inhabiting forms, as tree frogs and katy- 

 dids, the mottled gray and tawny of the mammals, birds, 

 lizards, and insects of the deserts, and the white of the hares 

 and foxes and owls and ptarmigan of the arctic and alpine 

 snow-covered wastes, are color tones obviously in harmony with 

 the general color of the environment. In the brooks most fishes 

 are dark olive or greenish above and white below. To the birds 

 and other enemies which look down on them from above, they 

 are colored like the bottom. To their fish enemies which look 

 up from below, their color is like the white light above them, 

 and their forms are not clearly seen. The fishes of the deep sea 

 in perpetual darkness are violet in color below as well as above. 

 Those that live among seaweeds are red, grass-green, or olive 

 like the plants they frequent. The difficulty of distinguishing 

 a quiescent moth from the bark on which it is resting, a green 

 caterpillar or leaf-hopper or meadow grasshopper from the 

 leaf to which it clings, a roadside locust from the soil on which 

 it alights, is a difficulty which has to be reckoned with by 

 every collector. 



Now while there are few human collectors of insects, there 

 are hosts of bird and toad and lizard insect-hunters, to say 

 nothing of the many kinds of predaceous insects which use their 

 own cousins for chief food. So that where this difficulty of 

 distinguishing the resting insect from its environment is suffi- 

 cient to postpone success on the part of the insect-hunting 

 bird or lizard, the life of the protectively colored insect is 

 obviously saved, for the time, by its dress. This is a utility of 

 color and pattern than which there can be, from the insect point 

 of view, nothing higher. 



One special point should be noted in connection with the 

 general protective resemblance, and that is, that the harmon- 

 izing or melting into the environment may often be accomplished 



