THE EVOLUTION OF THE CATERPILLAR 629 



beneath the soil. At this time, however, its green colour has 

 faded, and, in its place, the whole of its back becomes a dirty 

 brown shade, making it far less conspicuous on the earth. This 

 can hardly be held a mere coincidence. Another example is 

 that of the Swallow-tail caterpillar. When very young, this 

 creature feeds in the flowerheads of fennel and the middle of 

 its body, which is dark green, is crossed by a broad white 

 band, so that it is by no means easily picked out on the flowers. 

 When it moults, it loses the white patch and becomes uni- 

 formly light green, with black rings and red spots, and, although 

 it may not be regarded as a very striking example of protective 

 coloration, its new form is certainly better adapted to its new 

 position among the bright green fennel leaves than the earlier 

 white marked stage would be. 



However we may regard any individual case which seems 

 to present difficulties, the fact stands out that variation in form 

 increases progressively with the advance from secluded habits 

 of life to the active ones of the open, reaching the maximum in 

 the diurnal butterflies. 



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