18 
per cent., the number of ants per hundred hills to ninety-five per 
cent., and the number of root-lice per hundred hills to eighty-six per 
cent. Comparing similarly plat B with plat C, we find that the ef- 
fect of disking twice was to reduce the number of hills of corn in- 
fested by ants to forty-one per cent., and the number infested by 
root-lice to twenty-five per cent., and also to reduce the number of 
ants per hundred hills of corn to thirty-five per cent., and the number 
of root-lice per hundred hills to sixteen per cent. Still more briefly 
stated, the root-louse infestation was reduced approximately fifteen 
per cent, by disking once ; and seventy-five per cent, as to the num- 
ber of hills infested, or eighty-four per cent, as to the number of 
root-lice in the field, by disking twice (see experiment 5, Table V.). 
A comparison of the early-planted part of section C, in which 
fifty hills were examined, with the late-planted part of section B, 
in which twenty-five hills were examined, gives a surprising contrast. 
It will be remembered that all the latest-planted sections received 
an additional pulverizing just before planting, — necessitated, in 
the owner's judgment, by the packing effect of a heavy rain while 
the planting of the field was in progress. If this circumstance be 
taken into account, then it may be said that a comparison of these 
two areas indicates that three times disking — the last time soon after 
a heavy packing rain — may reduce the number of hills infested by 
ants to nineteen per cent., and the number of ants themselves to three 
per cent., and may obliterate the root-lice entirely, since none were 
found in the twenty-five hills searched in the late-planted part of 
section B. 
The effect of a single disking, following closely upon a beating 
rain, as shown by counts made in each of the three sections before 
and after these events and by averaging the percentages for the 
three plats, is as follows : The hills infested by ants were reduced 
to forty-three per cent, and the ants themselves to ten per cent, of 
the number to be found in those parts of the field which had not 
been disked after the rain, while the root-lice were reduced by the 
same treatment, to thirty-six per cent, in the number of hills infested 
and to eleven per cent, in the number of insects in the field. 
A further instructive conclusion may be derived from the obser- 
vations of May 31 by comparing the product of fifty badly infested 
hills with the remaining 225 dug up on that day. The total number 
of root-lice found in the fifty hills was 5254, averaging over 105 per 
hill, while the total in the 225 hills was 1068, or an average of five 
per hill. If these two collections of root-lice be compared with 
reference to the percentage of the adults which have developed 
wings, added to the pupae, which would acquire them at the next 
