ADAPTATION FOR THE INDIVIDUAL III 



background on which they lived. The only caterpillar 

 which was effectively hidden from his enemy was the 

 one that was indistinguishable on the leaf. If it es- 

 caped in this way, the probabilities are that it would 

 produce young which would be at least a little more 

 likely to be green in color than the progeny of its 

 darker-colored brothers and sisters. By this contin- 

 ued process the birds steadily weed out the darker- 

 colored specimens. There would result, in the course 

 of time, a race of caterpillars, whose ancestors for so 

 many generations back had been light green in color, 

 that there is little likelihood of any of the older and 

 darker forms turning up again. In the course of time 

 all dark tendencies will have disappeared from the 

 family and practically all of the group will be light 

 green. Any sport or variation in the shape of greater 

 conspicuousness would fall a quick prey to the enemy 

 and its line be cut off forever. 



The same sort of activity has resulted in the pe- 

 culiar green color of the katydid. This creature lives 

 chiefly upon the leaves of trees and shrubs. This in- 

 sect is so large that, even though it is leaf-like in color, 

 it might still be conspicuous. As a result those katy- 

 dids whose wings were most like leaves in form were 

 least likely to be picked up by the passing bird. This 

 sort of protective appearance is intensified by exactly 

 the same means as that which brought about protec- 



