INSECTS INJURIOUS TO CORN 153 



chambers of the ants' nests. On warm days the ants bring 

 them up to the warmer surface soil and in cold weather carry 

 them far down into the unfrozen earth. With the appearance 

 of young smartweed and foxtail-grass in April and May the eggs 

 commence to hatch. The ants at once lay bare the roots of 

 these plants and carry their young wards to them, where large 

 colonies soon become established. If the field is not planted in 

 corn, the lice will feed later upon the roots of pigeon-grass or 

 purslane. In early May lice, the second generation, commence 

 to appear, among them being both wingless and winged forms. 

 This brood and all of these during the summer are produced by 

 females known as agamic females, which give birth to live young 

 without mating with a male. As soon as corn plants are available 

 the ants again transfer the aphids to their roots, and carry any 

 winged aphids which may have spread over the field down on 

 to the roots of the corn. All through the summer the ants 

 attend the lice, burrowing around the roots of the corn, and 

 carrying them from plant to plant, in return for which the 

 aphids give off the sweet honey-dew, when stroked by the ants' 

 antennae, upon which the ants feed. During the summer the 

 aphids continue to reproduce with extreme rapidity, an aphid 

 maturing and giving birth to young about eight days after it is born, 

 each generation taking about sixteen days and there being about 

 twelve generations during the season. Both winged and wingless 

 agamic females occur throughout the summer, but late in Sep- 

 tember and in October wingless forms which develop into true 

 males and females are produced. These mate and the females 

 lay eggs during October, most of them being carried by the ants 

 to their nests, where the eggs are laid. 



Control. Owing to the fact that the aphids do not migrate 

 until the second generation, a rotation of crops will be of great 

 service in checking their injuries, as corn planted on uninfested 

 land will not be attacked until it has been able to secure a good 

 start, and if well fertilized will be able to withstand successfully 

 whatever injury may occur. Rarely is corn on land not in corn 

 the previous year seriously injured, and where infestation has 

 not been serious throughout a community, it may usually be 

 grown two years in succession with safety. 



