FIELD EXPERIMENTS ON THE CORN ROOT-APHIS ■ 
{APHIS MAIDIRADICIS FORBES). 
The corn root-aphis, wintering as an tgg in the nests of ants in 
corn fields, begins to hatch, according to our observations in central 
Illinois, about April 8, and may continue this process for as much as 
six weeks, or until the latter part of May.* The earliest individuals 
of this first generation get their growth in approximately twenty 
days, and then give origin at once to representatives of the second 
generation, which in eighteen or nineteen days may themselves be- 
gin to reproduce. The growing period for an individual of the third 
generation is approximately eleven days, making a total of not far 
from fifty days for the entire life of a series of the first born of the 
first three generations from the egg. That is, by the last of May 
the latest to hatch of the first generation would coexist in the fields 
with the earliest born of the third generation. All hatching from 
the egg are wingless females, but a small, and no doubt variable, 
percentage of the second and third generations are winged, and 
leave their underground quarters to fly abroad and start new col- 
onies elsewhere. The later steps of this life history are not neces- 
sary to a discussion of the experiments here reported. 
In view of the fact that the young lice are dependent upon their 
attendant ants, at least until they have been placed upon the roots of 
plants suitable for their maintenance, it has seemed to me prob- 
able that an early and repeated stirring of the ground infested by 
these insects in early spring, scattering the eggs and young aphids 
again and again through the dirt, and killing the young weeds in the 
corn field upon which they must at first depend for food, would 
have the effect to destroy great numbers of them and thus to weaken 
the force of the aphis attack upon the young corn at a time when it 
is most susceptible to injury. 
The Season of 1904. 
With a view to testing this supposition,, a field experiment was 
arranged in the spring of 1904, to be made in two neighborhoods 
notorious for some years for an abundance of the root-aphis on 
corn and a considerable injury to the crop in consequence. Circum- 
stances beyond my control prevented, last year, as early a beginning 
as might have been desirable, and nothing was done in the experi- 
*We have this year collected eg-g-s of the corn root-aphis from ants' nests in the field May 
19. These eg-g-s hatched under our observation, and the young were maintained on corn, but 
were not kept until mature. 
