COLOR AND PATTERN IN ANIMALS 399 



in such a case is to be sought in utility. The usefulness of 

 color in animate nature as an inspirer and satisfier of our own 

 aesthetic needs and capacities, or of color patterns as means 

 whereby we may distinguish and recognize various sorts of 

 animals and plants, is a usefulness which may be answer enough 

 to the passing poet on the one hand, and to the old-line Lin- 

 nsean systematist on the other, but it is, of course, no answer 

 to science. Science demands a usefulness to the color-bearing 

 organisms themselves: and a usefulness large and serious 

 enough to be the sufficient cause for so highly specialized and 

 amazing a development. 



The explanations, of some of the color phenomena of animals 

 are obvious: some uses we recognize quickly as certain, some as 

 probable, some as possible. Some colors are obviously there 

 simply because of the chemical make-up of parts of the insect 

 body. That gold is yellow, cinnabar red, and certain copper 

 ores green or blue, are facts which lead us to no special inquiry 

 after significance: at least, not after significance based on 

 utility. If an insect has part of its body composed of or con- 

 taining a substance that is by its very chemical and physical 

 constitution always red or blue or green, we may be content 

 with knowing that, and not be too insistent in our demand to 

 the insect to show cause, on a basis of utility, for being partly 

 red or blue or green. And even if this red or blue be disposed 

 with some symmetry, some regularity of repetition, either 

 segmentally or bilaterally, this we may well attribute to the 

 natural segmental and bilaterally symmetrical repetition of 

 similar body parts. Some color and some color pattern, then, 

 may be explicable on the same basis as the color of a mineral 

 specimen or of a tier of bricks. 



But no such explanation will for a moment satisfy us as 

 to the presence of and arrangement of colors in the wings of 

 Kallima, the dead leaf butterfly, or in Phyllium, the green leaf 

 phasmid, or in the butterfly fish, Chcetodon, or in the lichen 

 spider, or in the chameleon with its changing tints, or in any 

 one of a score of other more or less familiar forms whose color 

 pattern makes, even on the casual observer, an insistent 

 demand for rational explanation. 



Certain uses of color seem apparent: the colored eye flecks 

 or pigment spots of many of the lower animals presumably 

 serve their possessors as organs by which to distinguish the 



