28 
The effect of twice disking, as shown by a comparison of C i 
and B I of the Hinman field (Table III.) was to reduce the number 
of infested hills by fifty-nine per cent, for the ants and seventy-five 
per cent, for the aphids, and the number of insects by sixty-five per 
cent, and eighty-four per cent, respectively. As these two treat- 
ments were given, however, on the 5th and 8th of May, and the 
inspection was not until twenty-three days later, it is probable that 
the full effect of this treatment does not appear in this statement of 
the result, since there was ample time for the treated plats to become 
restocked by both ants and aphids by multiplication and migration 
and by the establishment of new aphis colonies from winged parents 
developed during this interval. 
The general conclusion to be drawn from this whole series of ex- 
periments is to the effect that the number of both ants and aphids 
may be readily controlled and the injuries to corn in great measure 
prevented by thorough and frequent stirring of the ground pre- 
vious to corn planting, and that the disk harrow or its equivalent is 
much the best implement for the purpose. Indeed, the treatment 
most effective for the destruction of the root-aphis and its attendant 
ant in spring is in great measure that which will be found most use- 
ful as a thorough preparation of the soil for corn, the main differ- 
ence being that a thorough overturning and stirring of the soil is 
the essential thing for the destruction of the root-louse, while it is 
sufficient for the corn plant if the earth be merely pulverized in 
place. 
If the corn farmer will prepare his old corn ground early and 
thoroughly, using the plow and the disk harrow by preference, he 
should have little trouble in the beginning of the season from the 
corn root-aphis, and so fast and so far as the general community acts 
in accordance with this idea, to that extent will later injuries by this 
aphis be forestalled. It is in this as in many other cases, one acting 
by himself alone can accomplish relatively little even for his own 
protection ; the welfare of each depends on intelligent cooperation 
by all. 
It is further to be concluded from the observations here re- 
ported, that if infested corn ground be planted to oats, the root-lice 
will leave it or perish in it (just which we do not yet know) by 
the end of May. A rotation with a short period in corn must con- 
sequently act to check the multiplication of this insect and to dimin- 
ish its injuries to corn. 
