ADAPTATION FOR THE INDIVIDUAL lit 
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- 
