172 
Topical Applications to the Roots. 
The first appearance of the root-worms in a field can usually be 
detected by the dwarfed aspect of patches of the plants, which 
apparently cease to grow. It is not impossible that at this time 
effective use could be made of some insecticide which should arrest 
the progress of the difficulty by destroying the larvae m the ground 
in these 5 isolated areas. With a view to testing partially the prac¬ 
ticability of this method, I arranged, in December, the conditions of 
a series of experiments with bisulphide of carbon and carbolic acid, 
which experiments were carried out by Mr. Garman at the Labora- 
torv For this purpose, full-grown living larvae of Sceloclonta pubes- 
cens were obtained December 7, in Southern Illinois, where they 
were at this time hibernating. ! 
Bisulphide of Carbon. 
Experiment 1.—On the 14th of December, one of these larvae was 
placed under a small glass dish, with a bit of sponge containing a 
drop or two of bisulphide of carbon. The larva at once began to 
roll about, as if suffering from the effects of the vapor, and at the 
end of two minutes was apparently dead. At the end of ten minutes 
it was taken from under the dish. Twelve minutes later it showed 
signs of life, but in an hour and twenty minutes it was dead. 
Experiment 2.—Two living larval of Scelodonta were placed in a 
piece of thin muslin with a little earth, and then buried at the 
bottom, near one end, of a crayon-box of earth*. A small hole was 
then made in the earth near the opposite end of the box, and about 
half a teaspoonful of bisulphide of carbon was poured into it, the 
hole being filled with earth. In fifty-five minutes the larvae were 
apparently dead, but an hour and twenty minutes later one showed 
signs of life. In forty minutes more this one was evidently recover¬ 
ing and two and one-half hours later was apparently unharmed, 
while the other larva seemed dead. Eight hours after the adminis¬ 
tration of the bisulphide, the second larva showed some signs of 
life, but in twenty-five hours this one was evidently dead; the first, 
however, recovered. 
Experiment 8.—This experiment was. a repetition of the preceding, 
but with less satisfactory results. Five hours after treatment the 
larvae were both alive, and were then returned to the earth and 
again treated to bisulphide of carbon as at first. Two and one-fialt 
hours later they were found to be still alive. 
Experiment 4.—In this experiment, two .larvae were placed in the 
earth as before, a teaspoonful of bisulphide of carbon was poured 
into a hole made in the middle of the box, consequently about 
three inches from the buried larvae. One hour later both insects 
were seemingly dead, and in sixteen hours were evidently past 
recovery. 
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* The boxes of earth used in these experiments were 6 M inches long by 4 inches wide, 
and 3% inches deep. 
