156 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



barley, as to do considerable injury. This species is also of interest 

 in that it appears on corn foliage in midsummer at the time when 

 the numbers of the root-aphis commence to decrease on the roots, 

 and it was for many years thought to be the same species. Care- 

 ful rearing experiments made under the direction of Dr. S. A. 

 Forbes have failed to show any connection between the root- 

 aphis and leaf-aphis, the aphids from the roots being unable to 

 establish themselves on the leaves and those on the leaves never 

 migrating to the roots.* 



Dr. Forbes describes the species in his twenty-third report 

 as follows: " In the latter part of the summer this bluish-green 



FIG. 131. The com leaf-aphis (Aphis maidis Fitch): winged female much 

 enlarged. (After Webster, U. S. Dept. Agr.) 



plant-louse may occasionally be found on the younger leaves, 

 the tassel, and the upper part of stalks of corn, and more abun- 

 dantly and frequently on broom-corn and sorghum. Multiply- 

 ing in place by the birth of living young, which do not wander 

 from their place of origin, these leaf-lice may become abundant 

 enough to kill the leaves and to some extent to affect the health 

 of the plant. The insect is, however, rarely seriously injurious 

 to corn, but there is some evidence, . . . that it may prevent the 

 fertilization of the kernel by sucking the sap from the silk and 

 killing it before it has performed its function. Heavily infested 



* S. A. Forbes, 13th, 16th, 18th, and 23d Reports of the State Entomologist 

 of Illinois. 



