VIII ORIGIN AND USES OF COLOUR IN ANIMALS 205 



of a geometer two inches long. I showed it to several members 

 of my family, and defined a space of four inches in which it 

 was to be seen, but none of them could perceive that it was a 

 caterpillar." 1 



One more exami:»le of a protected caterpillar must be 

 given. Mr. A. Everett, writing from Sarawak, Borneo, says : 

 " I had a caterpillar brought me, which, being mixed by my 

 boy -vvith some other things, I took to be a bit of moss with 

 two exquisite pinky- white seed-capsules ; but I soon saw that 

 it moved, and examining it more closely found out its real 

 character : it is covered with hair, with two little pink spots 

 on the upper surface, the general hue being more green. Its 

 motions are very slow, and when eating the head is with- 

 drawn beneath a fleshy mobile hood, so that the action of 

 feeding does not produce any movement externally. It was 

 found in the limestone hills at Busan, the situation of all 

 others where mosses are most plentiful and delicate, and 

 Avhere they partially clothe most of the protruding masses 

 of rock." 



Hoiv these Imitations liave been Produced. 



To many persons it will seem impossible that such beauti- 

 ful and detailed resemblances as those now described — and 

 these are only samples of thousands that occur in all parts of 

 the world — can have been brought about by the preservation 

 of accidental useful variations. But this will not seem so 

 surprising if we keep in mind the facts set forth in our 

 earlier chapters — the rapid multiplication, the severe struggle 

 for existence, and the constant variability of these and 

 all other organisms. And, further, we must remember 

 that these delicate adjustments are the result of a process 

 which has been going on for millions of years, and that we 

 now see the small percentage of successes among the myriads 

 of failures. From the very first appearance of insects and 

 their various kinds of enemies the need of protection arose, 

 and was usually most easily met by modifications of colour. 

 Hence, we may be sure that the earliest leaf- eating insects 

 acquired a green colour as one of the necessities of their 

 existence ; and, as the species became modified and specialised, 



^ Nature, vol. iii. p. 166. 



