142 THE MEANING OF EVOLUTION 



When the katydids arrive their jaws are young and 

 tender, but so are the leaves upon which they are born. 

 Hence there is httle difiiculty on the part of the young 

 katydids in finding an abundance of food. By the 

 time the leaves have grown tougher, the katydid's 

 jaws are stronger, and the leaves will still serve as 

 food. 



Everyone who is at all familiar with country life 

 and gardening is familiar with what is called the po- 

 tato or tomato worm. It is a long, green, smooth, 

 caterpillar, as long and as fat as your linger and pro- 

 vided with a horn upon his tail. The gardener may 

 not know that after a while this creature will burrow 

 into the ground, and there change into an oblong 

 brown mass with a sort of a pitcher handle at one 

 side. Next year this pupa will split down the back, 

 and from out of the brown case will come a hawk- 

 moth, which soon will fly with rapidly quivering wings 

 and feast upon the nectar of our moon flowers or on 

 that of the "Jimson" weed. Those who have cleaned 

 these pests from the potato or tomato vines will often 

 have noticed one of them covered with wdiat look al- 

 most like grains of rice. This appearance reveals an 

 interesting story. Some time earlier an insect that 

 looked very much like a dainty wasp with a rather 

 long sting in its tail hovered over the caterpillar. This f 

 is the ichneumon fly. Eventually lighting upon the a 



