WARNING COLOUES 205 



has been discovered. The part seized by the enemy 

 breaks away, and thus gives the animal another chance 

 of escape. The cases differ, however, from the pre- 

 ceding ones in that the enemy is in no way injured 

 by its mistake. In correspondence with this difference 

 such features are associated with Protective Kesem- 

 blances leading to concealment, and are not them- 

 selves highly conspicuous, or are only conspicuous 

 when the animal is thoroughly on the alert. The 

 object of these characters is to direct attack to some 

 unimportant part after all other methods of defence 

 have failed, after disguise has been penetrated or 

 speed surpassed. 



This is probably one of the meanings of the 

 brightly-coloured wings of butterflies, in addition to 

 their more obvious use in courtship. When the insect 

 is flying they form a conspicuous mark easily seized 

 by an enemy, and yet readily tearing without much 

 injury to the insect. On this account we generally 

 find the wings torn and notched when an insect has 

 been long on the wing. 



In the spring of 1888 I caught a large number of 

 Clouded Yellow Butterflies (Colias edusa) in Madeira. 

 The limited number of species in the island (there 

 are only about a dozen), and the abundance of 

 small omnivorous lizards and of insect-eating birds, 

 lead to the keenest pursuit of the butterflies, and I 

 noticed that the hind wings of a considerable pro- 

 portion of the Clouded Yellows were notched just 



