13 
would still further diminish and mask the effect of the treatment. 
In other words, if an entire field is treated, the benefit will be greater 
than where only an experimental plat is used, and the results of 
treatment here given are less than they should be if they are cor- 
rectly to indicate the probable effect of the procedure used. 
It should be noticed further that the treatment of the Coolidge 
and the Doerr fields was different especially in the fact that the lat- 
ter was harrowed three times while the Coolidge field was disked 
three times. As the harrow tooth does not penetrate the earth to 
so great a depth a? the disk, and does not move the dirt so far or 
mix it so well, much of the difference in result is probably attribu- 
table to this difference of implements. 
Table II. Abstract of Doerr Experiment, 1904. 
(Planted June 2; examined June 14.) 
Plat A 
Plat B. 
*Spaded (.5), 
harrowed twice (6, 9) 
75 hills examined 
*Plowed (1), harrowed (2). 
spaded (3), harrowed (4), 
spadea (5), harrowed (O), 
rolled (7), harrowea 
twice (8, 9) 
100 hills examined 
Per cent. 
of 
hills infested 
Number of 
insects per 
hundred nills 
Per cent. 
of 
hills infested 
Number of 
insects per 
hunared hills 
Ants 
Apbids 
62 
44 
1961 
1464 
25 
11 
630 
198 
1. Plowed May 23. 2. Harrowed May 2.5. 3. Spaded (with spadin? harrow) May 86. 
4. Harrowed May 28. 5. Spaded June 1. 6. Harrowed June 3. 7. Rolled June 11. 8. Har- 
rowed June 11. 9. Harrowed June 13. 
The Season oe 1905. Bradford^ Illinois. 
For a further test of agricultural measures against the corn root- 
aphis, I planned and provided for a field operation to begin as early 
as practicable in the spring of 1905, in a neighborhood in Stark 
county to which my attention had been especially called by the fol- 
lowing letter of March 1 1 from Messrs. Deyo and Foster, real estate 
agents at Bradford, 111. 
"The farmers here are troubled with lice on the roots of the 
corn. Even on good ground we find that the roots are alive with 
them and the corn makes a very poor growth until about harvest- 
time. If we have rains it makes a fair yield, but blows over very 
*See note to Table I., p. lOS. 
