CORN PESTS AND DISEASES 253 



of grass might He unchanged for several years, being 

 plowed when broken up in late summer or early fall 

 and sown to clover in the spring, either with oats or 

 on winter wheat or rye sown the fall before. The 

 clover should be allowed to stand a second year, and 

 might be followed with corn, with positive assurance 

 that the wireworms originally in the sod would by that 

 time have entirely disappeared. 



Seed Corn Maggots — Two somewhat common 

 injuries to seed corn in the ground are due to small 

 white maggots without legs, one apparently headless, 

 with much the form and general appearance of a very 

 small blowfly larva, and the other with a smooth, con- 

 spicuous head of a shining jet black color. The first is 

 called the seed corn maggot and infests corn only, so 

 far as is known. The second is the black-headed grass 

 maggot, injuring corn only when it follows grass. 

 Both these maggots penetrate the kernel, feeding on 

 the mealy inner part, leaving the outer shell. The 

 former transforms during the summer to a small two- 

 winged fly similar in form to the house fly. The latter 

 becomes a slender small black gnat, somewhat resem- 

 bling the mosquito. The fly is not likely to be noticed, 

 but the gnat of the grass maggot is often seen in large 

 numbers near the ground in early spring. The seed 

 corn maggot penetrates the grain commonly after 

 it sprouts but before it appears above ground, killing 

 the germ or the growing shoot and finally hollow- 

 ing out the interior so as to leave only the harder 

 outer part of the kernel. Unsprouted kernels softened 

 by lying in the earth are also frequently penetrated 

 in a way to destroy the germ, as shown in the illustra- 

 tion (Fig 61). The adult is a small two-winged fly, 

 about a fifth of an inch long, and not unlike a house 

 fly in general appearance. There is evidence that only 

 a single brood a year occurs. 



