95 
TOBACCO SMOKE. 
The difficulty of reaching all the worms in a cabbage head by any 
application of a powder or liquid, after the head is pretty well 
grown, and especially after the worms have commenced to penetrate 
it, made it desirable to find some vapor which might be easily ap- 
plied in a way to reach all the insects with destructive effect. Hx- 
periments were consequently made—first with tobacco smoke. Three 
cabbage worms were confined under a bell-jar, and exposed to the 
smoke of a cigar for ten minutes. A full-grown worm was scarcely 
at all affected. Both the smaller ones, a little over half an inch in 
length, were nearly lifeless, when removed from the jar. In a few 
hours, however, they had entirely recovered, and were apparently 
uninjured by their experience. Five individuals were next selected, 
ranging from half an inch in length to full-grown specimens, and 
were exposed to the smoke as before, for ten minutes, under a glass 
jar. All except one of the largest were badly affected, the three 
smaller being apparently nearly dead. In an hour and a half the 
two larger ones were crawling about, but two of the others were 
apparently killed. In two hours more, however, all were crawling 
about except one, and that showed evident signs of life, and prob- 
ably would have recovered in time. No experiments were tried with 
longer exposure, because, even if successful, it would be found im- 
practicable to apply tobacco smoke for a longer time in the field. 
SULPHUR. 
For some reason which I do not now remember, I thought it 
worth while to try a single experiment with the fumes of sulphur. 
One proved to be sufficient. The record is brief and conclusive :— 
exposed two minutes; plant killed, worms uninjured. 
BISULPHIDE OF CARBON. 
The vapor of bisulphide of carbon was also used, not with any 
expectation of a practical application to cabbage plants, but to 
further test the hardiness of the worms. Two nearly full grown 
specimens were placed under a bell jar of about a gallon capacity, 
and about half a cubic inch of sponge was saturated with the fluid 
and placed under the shade with the worms. The effects were ap- 
parent in less than a minute, and in five minutes both the worms 
were rolling about, disgorging a green fluid. When the shade was 
removed at the end of ten minutes the worms were not dead, 
but completely torpid. In three-quarters of an hour they showed 
some signs of life, and in four hours were evidently slowly recover- 
ing. In three hours more they had completely regained their 
activity and crawled away. Again, three worms, one half grown, 
and the others of full size, were exposed under a smaller jar for 
the same length of time. When the glass was removed, none of 
them showed any sign of life. In three-quarters of an hour, how- 
ever, the young one was crawling about and the old began to move, 
and in two hours longer, all had recovered and disappeared. 
