q 
ne 
67 
prising. Apart from this general statement I have only to report the 
result of a single series of ‘plot experiments tried in 1891 with various 
fertilizers mingled with petroleum, crude and refined, as an insecticide, 
and with applications of salt, wood ashes, and lime. 
A plot of ground ten hills square, containing ninety-seven hills of 
corn, was selected on the University experimental farm at Urbana June 
18, 1891, and surrounded by a continuous line of six-inch boards sunk 
about three inches into the ground, with close-fitting joints, and with the 
earth well tramped both outside and in. The upper edge of the boards 
was thickly covered with coal-tar, subsequently kept fresh by repeated 
applications. These measures were intended to prevent all interference 
with the experiment, either by escape of the insects within the plot or 
by invasion from without. June 26 this enclosure was enlarged to con- 
tain twenty-three hills more. Fertilizers, and mixtures of fertilizers and 
petroleum, were applied to the hills of corn June 18 and 23, being 
worked into the soil about each hill; and on the 26th lime, ashes, and 
salt were similarly applied. Of the ninety-seven hills in the first en- 
closure, forty-eight were found in the beginning to contain root lice and 
ants, and of the twenty-three hills in the second lot sixteen were simi- 
larly infested. 
Three fertilizers were applied: superphosphates, muriate of potash, 
and sulphate of potash; each at the rate of three pounds to twenty ehills 
of corn, and in each case half the hills under experiment were treated 
with the pure fertilizer and the other half with a mixture of fifteen 
ounces of petroleum to three pounds. One third of the above amounts 
were applied June 18.—the petroleum in these cases being the crude 
Lima oil,—and the remaining two thirds, June 23, when refined petro- 
leum was used. The following notes are condensed from the memo- 
randum filed at the time by the assistant® in charge of the experiment: 
Experiment I., Superphosphates. Experiment II., Superphosphates and Petro- 
leum. 
June 29, TI. Ants and root lice numerous. 
29, II. Both insects present, but less numerous than in TJ, 
July 1, I. Ants and lice abundant. 
rs 1, II. Ants present but no lice. 
I. Ants and lice abundant. 
I. A few ants but no lice. 
I. Ants and lice comparatively abundant. 
I. Ants and lice both present but fewer than in T, 
Experiment Sine Muriate of Potash. Wxperiment IV., Muriate of Potash and 
Petroleum. . 
June 29, ITI. A few ants and lice found. 
“29, IV. Dead plant lice discovered in one hill, both ants and lice oc- 
curring generally but not abundantly. 
July 1, III. A few ants but no lice. 
~ 1, IV. Ants alone discovered on roots about one foot from the hill, 
just outside the fertilized area. 
oy 7, III. Ants and root lice found. 
7, IV. Ants but no lice. 
“15, III. Ants plentiful; lice common, 
“15, 1V. Few ants and lice detected. 
Experiment gan Sulphate of Potash. Experiment VI, Sulphate of Potash and 
Petroleum. 
June 29, V. Ants present but no lice. 
“29, VI. A few ants present but no lice. 
July 1, V. Neither ants nor lice were found. 
oy 1, VI. A few ants and lice in one hill. 
. 7, V. Ants and lice numercus. 
ss 7, VI. Both insects present. 
“ .15, V. No ants or lice detected. P yet ; 
15, VI. Small colony of ants and a few lice in one hill. 
*Mr. J. S. Terrill, now of the Agricultural Experiment Station of Kentucky. The 
work was, however, done under the immediate supervision of John Marten, one of 
my present entomological assistants. 
