BUTTERFLIES OF MAINE. 29 
Birds and spiders are of great service in destroying these 
insects, and poultry may also be made available to lessen 
their numbers if allowed to run among the cabbages. Chil- 
dren should be encouraged to capture and destroy the butter- 
flies, and the pupz should also be collected and destroyed, 
unless they are found to be infested with parasites, which can 
easily be determined by observing whether the joints of the 
abdomen can be moved easily or not. If they are flexible, 
they should be destroyed, otherwise they may contain para- 
sites and should be preserved, that the parasites may escape 
to attack others. 
Experiments with hot water, tobacco smoke, sulphur, bi- 
sulphide of carbon, saltpetre and salt, lime, tar-water, pyreth- 
rum and kerosene emulsion were tried by Prof. S. A. Forbes 
on this insect to ascertain what was the value of each respect- 
ively as an insecticide, and it was found that the last two alone 
would destroy the larve without injury to the plants, but 
these were of value only while the larvae were on the exposed 
parts of the cabbage, or before they had made their way into 
the interior of the head. As these butterflies lay their eggs 
continuously for some time, any application, to be entirely 
successful, must be repeated several times. 
The method of preparing the kerosene emulsion, as pub- 
lished by Prof. Riley, is substantially as follows. Kerosene 
oil is mixed with milk, either sweet or sour, and at a 
temperature of 75° F., they are churned together vigorously 
for fifteen minutes or more, when they form an emulsion, or 
curdle and suddenly thicken to form a white and glistening 
butter, perfectly homogeneous in texture. The whole amount 
of both ingredients solidifies together and there is no whey 
or other residue. The emulsion may be made of any desired 
strength, as the quantity of milk required to hold the oil does 
not exceed ten per cent. After the emulsion is made, it can 
be diluted with water to any extent required by adding a 
little at a time and stirring it up well. Prof. Forbes obtained 
good results with an emulsion diluted so that the kerosene 
was five or six per cent of the whole mixture, and sprinkled 
on to the plants. 
