442 THE ANIMALS AND MAN 



beautiful on humming-birds. On the other hand the red 

 brown of the robin's breast and the yellow of the meadow 

 lark's are produced by feathers containing reddish and 

 yellowish pigment granules. 



The colors of most quadrupeds, which are covered with 

 hair, are dull and almost entirely due to pigment in the 

 hair. Those of live fishes, often brilliant and iridescent 

 in the water, fade and sometimes wholly disappear when 

 the fish is dead and dry. Colors such as these are struc- 

 tural, the scales being mostly transparent. 



Observe as many animals as possible and try to find 

 out how their colors and markings are produced, what 

 the external structures are which make them, and whether 

 they are made by pigment or by prismatic reflection. 



Fig. 228. Diagram to show the shingling arrangement of the scales over 

 the surface of a butterfly's wing; the short black bars indicate scales 

 in cross-section, and the broad central bar, the wing in cross-section. 



Uses of color. — Although we have been long accus- 

 tomed to see the beautiful and varied markings of birds 

 and butterflies, have we asked ourselves of what use these 

 colors and patterns are to the animals possessing them? 

 We cannot think that they exist just to please us. We 

 have found that in animals' bodies the parts are all made 

 so as to be just as useful as possible, each part having some 

 special thing to do to help the animals live successfully. The 

 same is true of the colors and patterns which are such con- 

 spicuous features of their external appearance. 



Try to catch a locust. The insect will be plainly seen 

 as it flies or leaps through the air, but how when it alights 

 on the ground? If you do not watch carefully to see it 

 alight, you will have great difficulty in finding it now. It 

 is almost indistinguishable among the pebbles, bits of twigs, 



