Oct. 16, 1916 
Effects of Nicotine as an Insecticide 
97 
At 11 o'clock the upper surface of a large dock leaf (Rumex sp.) was 
sprayed heavily with the nicotine solution (1 : 100) in the greenhouse. 
A comparatively large nasturtium leaf was placed directly over and 
one-half inch above the dock leaf. The under surface of each leaf 
bore many aphids. At 2 o'clock all the aphids on the underside of the 
nasturtium leaf were dead, while none on the dock leaf apparently had 
been affected. 
(c) ODOR FROM EXTRACT OF POWDERED TOBACCO 
Catalpa leaves were sprayed heavily with the extract of powdered 
tobacco described on page 93. After these leaves had become per¬ 
fectly dry in the sun, they still emitted a faint nicotine odor. At 1 
o'clock many small caterpillars (6 to 10 mm. in length) of the catalpa 
sphinx were then tested by being placed inside battery jars in the man¬ 
ner already described. At 1.10 o'clock a few of them were dying; at 
2.25 four-fifths of them were dead. These had not eaten of the leaves. 
The remaining ones did not die until three days later; they had eaten 
the leaves to a limited degree. 
The preceding experiment was repeated twice by using large fall 
webworms on mulberry leaves (Morns sp.) that had been submerged 
for two minutes in the extract and had been dried in the current of air 
from the electric fan. The first lot of caterpillars ate the leaves readily 
and apparently were not affected, but a third of the second lot was 
dead the following morning, after having slightly eaten the leaves. 
(d) ODOR FROM SOLUTION OF NICOTINE SULPHATE 
The experiment just preceding was repeated twice by using a solution 
of nicotine sulphate (1 : 1,200). The results obtained with the first lot of 
fall webworms showed that only, one caterpillar was killed, but the 
leaves were not much eaten. Relative to the second lot, the leaves were 
not eaten at all. Two hours after being placed on the leaves, many 
of the caterpillars became stupid and a few showed signs of dying, but 
were not found dead until the following morning. Two days later still all 
of them were dead. 
The preceding was repeated by heavily spraying catalpa leaves with 
a much stronger solution of nicotine sulphate (1 : 64) and by using 
small caterpillars (6 to 10 mm. in length) of the catalpa sphinx. At 
12.52 o'clock these leaves had become perfectly dry in the sun; at 12.56 
a few of the caterpillars acted as if dying; at 2.25 all of them were dead. 
The leaves gave off a slight nicotine odor and had not been eaten. 
The preceding was repeated by dipping Carolina poplar leaves into 
the same solution and by using the aphids removed from these leaves 
after the latter had been dried in the current of air from the electric 
fan. The following morning most of these aphids were dead. 
