420 



EVOLUTION AND ANIMAL LIFE 



structures at the anal angle of the hind wing, under side, in 

 many Lyccenidcc, to a head with antenna 4 and eyes/' and recalls 

 that this has been independently noticed by many other ob- 

 servers. The movements of the hind wings by which the tails, 

 which appear like antenna, are made continually to pass and 

 repass each other, add greatly to this resemblance. 



Very many species of animals, especially among the verte- 

 brates, possess certain distinctive and striking markings, which 



c I 



FIG. 262. The butterfly fish, Chcetodon ragabundus. from Samoa. This small fish is 



most strikingly colored. 



have been supposed to serve as recognition marks to other 

 animals of the same species. In this theory, these marks afford 

 a swift means of knowing friends from enemies. Of this 

 nature are the white tufts at the tail of the cottontail rabbit, 

 the black patch of the blacktail deer, the flanks of the Rocky 

 Mountain antelope, the concealed scarlet crest of the kingbird, 

 the fiery shoulder of the redwing blackbird, the blue speculum 

 of the duck, the black bars and eye spots of the butterfly fishes 

 (Chcetodon), and the peculiar marks of one form or another 

 on a host of mammals, birds, reptiles, and fishes. 



It is very easy to indicate recognition marks. Keeler, among 

 others, has given an elaborate list of the principal cases among 

 American birds, and there is scarcely a species without one or 



