COLORS ^ND MARKINGS OF /INIMALS 285 



Colors of other animals. — The colors of other animals 

 are also produced in one or both of these two ways ; that 

 is, either by colored pigment, or by reflections from 

 structures which act as the prism does. Only a few 

 other animals have scales, and almost no others have 

 scales just like those of the butterfly, but they have other 

 kinds of structures on the outside of the skin, such as 

 feathers or hairs,' which contain pigment, or break up 

 white light into colors. 



Observe the coloring on a blackbird ; note the fine iri- 

 descent blue and purple or bronze-green reflections. 

 These are made by the feathers reflecting broken-up 

 white light. Such iridescent colors produced by struc- 

 ture, and hence called structural colors, are especially 

 pronounced and 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. 



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 



