ANIMAL AND INSECT ENEMIES 217 



replanting a field injured by wire worms the new rows are 

 planted midway between the old, leaving the old plants 

 as food for the worms. 



Note. The above pests, cutworms, grubs, and wireworms, give most 

 trouble on grass sod. They seldom give trouble after cultivated ciops 

 where clean culture has been practiced. 



There are two insects that are most troublesome where 

 continuous corn culture is practiced — the corn rootworm 

 and the root-louse. 



Corn rootworm 



There are two species, known as the Western and the 

 Southern corn rootworm. The larvse are similar and 

 work in the same way, though the beetles differ in color. 

 In early fall the female beetles lay about a dozen eggs in 

 the ground near the corn roots. These remain over winter 

 and hatch the next spring. The larvae are about the 

 size of a pin and two-fifths inch in length, almost colorless 

 except for the head, which is yellow. They do most harm 

 in July and August. Starting near the tip of a large root 

 they bore inside the root, toward the plant. As they 

 multiply rather slowly and as corn is their only host 

 plant, the rootworms are serious only where the land has 

 been in continuous corn culture for three or more years 

 in succession. 



Corn root-louse 



Injury from the corn root-louse is very irregular, due 

 no doubt to its natural enemies which ordinarily keep 

 it in check. When unrestrained, however, it increases so 

 rapidly that it may become very injurious in a short time. 

 Usually its injury occurs in spots rather than over the 

 whole field, due probably to local centers of infection 

 from which it spreads rapidly. During the summer the 



