9 
mental fields until May 13 in one locality, and May 23 in the other. 
I owe the opportunity to undertake the investigation at this time to 
Dr. J. W, Folsom, Instructor in Entomology at the University of 
Illinois, who was good enough to undertake the field inspections 
for me, and upon the report of whose observations the following 
statement of results is based. 
The season was at least a fortnight later than usual, and it is 
consequently difficult to say just what generations of the aphis were 
in existence at the time. Judging, however, by the calendar for the 
three earliest generations given above, and by the field and insectary 
work of 1905, reported farther on, it seems likely that the first and 
second generations were abundant in the fields, and that the third 
had not yet begun to appear. That the second was present is un- 
questionable, since occasional winged individuals. were found. 
The Galesbitrg Cultivation Experiment. (Table I.). — In the 
first experiment, made on the farm of Mr. J. H. Coolidge, about 
three miles from Galesburg, in Knox county, 111., two parts of a 
large field of corn were used, one of which (Plat A) received the 
usual treatment in preparation for planting and the ordinary culti- 
vation afterwards, while in the other, the experimental plat (Plat, 
B), the ground was repeatedly disked and harrowed between plow- 
ing and planting, and harrowed and cultivated promptly thereafter.* 
In this experimental plat were thirty-two rows, each eighty rods 
long, and in the check plat ninety rows of the same length. The 
latter was plowed early in May, planted May 13 to 17, harrowed 
once thereafter, and cultivated June 9, the condition of the corn with 
reference to ants and root-lice being there determined on the loth 
of June. The thirty-two experimental rows were plowed May 14 
to 16, the ground was thoroughly disked three times on the i8th, 
2ist, and 25th of May, also harrowed May 25, and planted on this 
same day. It was cultivated May 28, harrowed on the 30th, and 
inspected June 10. 
It will be noticed as an important difference between these two 
fields that the experimental plat was planted ten days later than the 
*The various operations on the ground used in these experiments were as follows: — 
First, plowing^ with an ordinarj' mold-board plow; second, harrowing- with a toothed 
harrow; third, disking with a disk harrow; lourth, spading witli a so-called spading- harrow; 
fifth, pulverizing- with a so-called "Acme" harrow, sometimes known and sold as a "pulverizer;", 
sixth, rolling with an ordinary smooth roller; seventh, cultivating with an ordinary "sulky" 
cultivator with shovels. These terms are used as above defined throughout this paper in 
both tables and text. The plowing- in the experimental plats was from five to seven inches 
deep; the toothed harrow stirred the earth, as a rule, to a depth of about two inches; the disk 
barrow commonly worked twice as deep or more, moving the dirt laterally and mixing- it 
thoroughly in the process; the spading harrow differed but little from the disk harrow in its 
operation except that it was likely to g-o deeper, and did not move the earth laterally to so 
g-reat a distance; the '-Acme" harrow, or "pulverizer," consisting of a row of blades set ob- 
liquely into an angular beam, followed by a transverse row of cjlindrical pointed teeth, worked 
to a depth of about three inches, as a rule, stirring and pulverizing the ground more effectually 
than the common toothed harrow, but not to the depth of the disks or moving it laterally as 
far. 
