112 THE MEANING OF EVOLUTION 



tive coloration. The katydid least leaflike in appear- 

 ance was eaten first Thus those most leaflike remain 

 until the last, and are most likely to produce young-. 

 Again, it was not the fact that they lived among 

 leaves which made them look leaflike, but it is because 

 they look like leaves that they escaped being devoured. 



The katydid has materially assisted in its own pres- 

 ervation by being active chiefly at night. In the day- 

 time it keeps comparatively quiet. Thus seated upon 

 a twig, especially if hidden among the leaves, it is al- 

 most unnoticeable. At night, however, it moves about 

 more freely, seeking its food and eventually its mate. 

 At such times it becomes distinctly more conspicuous 

 because its wings are steadily fluttering. The hind 

 wings are filmy and are very light green. The crea- 

 ture looks most ghost-like as it flies through the even- 

 ing air. 



A very similar history lies back of the coloring of 

 the ordinary toad. Though descended from the frog, 

 and originally a creature of the water, the toad has 

 long since adapted itself to live upon the dry ground. 

 It still produces its young in the water as it did when 

 a frog. Whereas the childhood of the frog, that is, 

 its tadpole stage, is very long and it assumes its adult 

 form comparatively late, just the reverse is the case 

 of the toad. The young hasten through their tadpole 

 stage within a few weeks, and assume the shape of 



