98 The Colours of Animals. 



Now for the brown colour. This probably makes 

 the caterpillar even more conspicuous among the 

 green leaves than would otherwise be the case. 

 Let us see, then, whether the habits of the insect 

 will throw any light upon the riddle. What 

 would you do if you were a big caterpillar ? Why, 

 like most other defenceless creatures, you would 

 feed by night, and lie concealed by day. So do 

 these caterpillars. When the morning light comes, 

 they creep down the stem of the food plant, and 

 lie concealed among the thick herbage, and dry 

 sticks and leaves, near the ground ; and it is ob- 

 vious that under such circumstances the brown 

 colour really becomes a protection. It might in- 

 deed be argued that the caterpillars, having become 

 brown, concealed themselves on the ground ; and 

 that we were, in fact, reversing the state of things. 

 But this is not so ; because, while we may say, as 

 a general rule, that (with some exceptions due to 

 obvious causes) large caterpillars feed by night and 

 lie concealed by day, it is by no means always the 

 case that they are brown ; some of them still retain- 

 ing the green colour. We may then conclude that 

 the habit of concealing themselves by day came 

 first, and that the brown colour is a later adapta- 

 tion. It is, moreover, interesting to note that while 

 the caterpillars which live on low plants often go 

 down to the ground and turn brown, those which 

 feed on large trees or plants remain on the under 

 side of the leaves, and retain their green colour. 



