BUTTERFLIES 67 



often gathered into circular groups, and so exactly 

 resembling the minute fungi on decaying leaves 

 that it is hard at first to believe that the insects 

 themselves are not attacked by some such fungus. 

 The concealment produced by this wonderful imita- 

 tion is most complete, and in Sumatra I have often 

 seen one enter a bush and then disappear like magic. 

 Once I was so fortunate as to see the exact spot on 

 which the insect settled, but even then I lost sight 

 of it for some time, and only after a persistent 

 search discovered that it was close before my 

 eyes." 



This example serves as an extreme case of what 

 is really a general law among butterflies. 



The mode in which this protective colouring is 

 acquired is explained by Natural Selection. At first 

 there is a more or less accidental resemblance. 

 Now large numbers of butterflies are killed by birds, 

 lizards, and other animals, and any whose mark- 

 ings and habits of perching rendered them less 

 easy to see would have a better chance of escaping 

 their enemies ; these, therefore, will survive and 

 transmit their peculiarities to their offspring ; the 

 survivors of these in turn transmitting the peculi- 

 arities in a more strongly marked form, and so the 

 protective colouring becomes more marked from 

 generation to generation and the unprotected ones 

 perish. 



Warning Colours. These are found in specially 

 protected individuals which are usually uneatable, 

 or at any rate unpalatable, and whose nastiness it 

 is desirable to advertise in order that they may 



