95 
KEROSENE EMULSION. 
The emulsion of kerosene which had previously been found 
effective with the chinch-bug and plant-lice, was next tried upon 
these worms. It was made of equal parts of kerosene and milk, 
and diluted at first with fifteen parts of water. Three full-sized 
worms were selected, with one half-grown, and thoroughly sprayed 
with the mixture. All showed evident signs of discomfort, the 
smaller ones being most affected; but in three or four hours all 
had fully recovered. A dilution of double the strength of the pre¬ 
ceding was next sprayed upon two full-grown worms, and two half¬ 
size. In four minutes all were writhing about upon the table, and 
in fifteen minutes were nearly lifeless. Five hours later two were 
dead, and the others helpless, and three finally died. A mixture of 
medium strength, containing one part to twelve of kerosene, was 
next applied to five of the worms, ranging from full-size down to 
about one-fourth grown. In half an hour all were badly affected, 
and the three smaller apparently dead. In forty minutes all showed 
signs of life. In three hours the larger ones were crawling about, 
while the smaller ones were torpid. Only one of the smaller worms 
finally died, and all the others recovered. 
From the preceding experiments it is clear that a mixture of 
about one part of an emulsion to eight or ten of water (kerosene 
five or six per cent.) will destroy the greater part of the worms, 
and if applied before the individuals are full-grown, would appar¬ 
ently kill about all of them,—in fact, it seems to be scarcely less 
efficient than pyretlirum, and is much cheaper, although the labor 
of preparation on any large scale would be very considerable. 
Neither of these insecticides can be used to advantage after the 
cabbage has headed up to any considerable extent, as the worms 
are then able easily to conceal themselves, and but few would be 
reached by the spray or powder. This was shown by a field exper¬ 
iment with the kerosene emulsion, one part of kerosene to twenty 
of water. Two heads were thoroughly wetted with the mixture applied 
with a small syringe, at 4:80 in the afternoon. One of these was 
rather large and solid, the other much less compact. All the worms 
exposed to the full action of the fluid were killed, but about nine- 
tenths of them escaped. The plant was not at all injured by the 
application. 
SALTPETRE AND SALT. 
Having seen frequent and very favorable mention of a solution 
of salt and saltpetre, as a means of ridding the cabbages of these 
worms, a solution of an ounce of saltpetre and four ounces of salt 
to two quarts of water was sprayed upon several worms without 
appreciable effect. Four full-grown worms were then thrown into a 
dish containing the fluid and left two minutes, but were not injured 
in any degree. Three others were kept in the solution for four 
minutes, and ten minutes later had recovered and crawled away. I 
conclude, therefore, that this insecticide would be effective only if 
applied in sufficient quantity and for a long enough time to drown 
the worms. 
