8 BUTTERFLIES IN DISGUISE 



creatures fond of grasshoppers, that in time they 

 will resemble in coloring the sand on which they 

 live ; it is impossible that they should not. Any 

 creature not specially protected by nauseousness, 

 or habit, or special device of some sort, must in 

 the very nature of things, if it is to live at all, 

 have some other ^^rotection, and that afforded by 

 color and pattern is by far the most common. 

 The world is made up of eaters and eaten, of 

 devices to catch and devices to avoid being caught. 

 We may apply the same reasoning to two kinds 

 of butterflies subject naturally to the same class of 

 enemies ; that is, living in the same region and 

 flying at the same time. If one has the slightest 

 advantage over the other in the fight for life, by 

 being, for instance, distasteful to one class of com- 

 mon enemies, so that these forbear to attack it 

 after experiment or by instinct (the result of ances- 

 tral experiments), and there be among the less 

 favored flock, here and there, an individual which, 

 under circumstances favoring it, such as distance 

 or shadow, may more often than its fellows be 

 mistaken by the enemy for one of its distasteful 

 neighbors through its possession of a little more 

 than usual of a certain tint on a part of the 

 wing, a little larger spot here, or more of the sem- 



