216 INSECTS AFFECTING THE INDIAN CORN. 



only the surface substance, but as they grow older 

 they devour the whole leaf. The larva? become full 

 grown in about a fortnight, when they spin thin, 

 brownish cocoons on the ground, and change to pupae, 

 to emerge ten days or two weeks later as moths. 

 There are two or three broods each season^ 



Remedies. — Spraying or dusting infested plants 

 with London purple or Paris green is the most prac- 

 tical remedy for this insect that lias yet been suggested. 



The Corn Aphis. 



Aphis maidis. 



The leaves and stalks of corn are often infested by 

 colonies of a small bluish aphis or plant-louse, the 

 majority of which are wingless, and the rest winged. 

 This is the Corn Aphis. It has been for a long- 

 while considered the aerial form of the Corn Root- 

 louse, but the latest investigations indicate that the 

 two are distinct species. 



The full life-history of this insect is not known. 

 It is probably the summer form of some species that 

 passes the fall, winter, and spring upon a tree or 

 shrub. The winged viviparous females appear upon 

 the corn early in summer and start colonies of 

 young lice which develop rapidly and continue to 

 multiply viviparously until the approach of cold 

 weather in autumn. Then a winged brood appears, 

 and leaves the corn, migrating, doubtless, to some 

 other plant, But where it goes, and where the 

 winged females that start the colonies in early sum- 

 mer come from, is not known. 



