96 
Journal of Agricultural Research 
Vol. VII, No. 3 
air from the electric fan for an hour, at the end of which time they were 
perfectly dry, but still emitted a very faint odor of nicotine. A slightly 
longer time in the sun was required before they became perfectly dry. 
Each bottle with its contents was placed inside a battery jar 5 inches in 
diameter by 11 inches in height. Normal and untreated insects were 
then removed with a camel's-hair brush from other leaves to the leaves in 
these bottles. A glass cover was placed over each bottle, and the insects 
were observed at regular intervals. 
To ascertain the effects of nicotine vapor on aphids and bees, the 
insects were either inclosed in a battery jar with nicotine spray material 
below them or with the spray solutions placed in watch glasses or on the 
leaves near the insects in the open. 
(a) ODOR FROM SOLUTION OR PURE NICOTINE 
Carolina poplar leaves were dipped into a solution of pure nicotine 
(1:100), placed in the current of an electric fan for an hour, and were 
then arranged as already described. At 11 o'clock aphids (Aphis popu- 
lifoliae) from other leaves of the same tree were transferred to the leaves 
treated with the nicotine solution. At 4.30 o'clock the aphids were 
slightly stupid. The next morning all of them were dead. Not one of 
the aphids used as controls died. 
One day aphids were killed by being placed in vials which a week 
before had contained some of the nicotine solution. These vials after 
having been used had not been washed, and a week later two of them 
were unintentionally used for collecting aphids in the greenhouse. By 
the time a dozen aphids had been put into each vial and closed with 
stoppers which had also been used a week before, most of the insects 
were dead, and the remainder of them were in the last stage of paralysis. 
An examination showed that the vials still gave off a very slight odor 
of nicotine. 
(6) VAPOR PROM PURE NICOTINE 
At 10.30 o'clock a large Carolina poplar leaf bearing many aphids 
was put into one of the battery jars. A small beaker containing 5 c. c. 
of pure nicotine was also placed inside the jar about 5 inches below the 
leaf. At 12 o'clock a few aphids were stupid; at 1 o'clock several were 
dead; at 4.30 most of them were dead; the next morning all of them 
were dead. 
A few cubic centimeters of a pure nicotine solution (1 : 100) were 
poured into each of seven watch glasses. A small wire screen was laid on top 
of each watch glass so that it did not touch the nicotine solution. Sev¬ 
eral cabbage aphids (Aphis hrassicae L.) were then placed on each wire 
screen. The smallest aphids died within 10 minutes, the medium-sized 
ones within 16 minutes, and the largest ones within 22 minutes. 
