INSECTS INJURIOUS TO CORN 



167 



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

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

 winged aphides 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 

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

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

 aphides continue to reproduce with extreme rapidity, an aphid 

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



FIG. 122. Grass root-louse (Schizoneura panicola); winged vivaparous 

 female, a, antenna. (After Forbes.) 



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 aphides 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 successfully withstand 



