INJURIOUS INSECTS. 93 



tion in water. This last method is believed to be the most 

 efficient. The greater part of the powder is dissolved in the 

 water, to which it at once imparts the insecticide principle. 

 Experiments have shown that half an ounce stirred in two 

 gallons of water will destroy all but the most hardy caterpil- 

 lars and such as are protected by long dense hairs. For 

 these a stronger solution is necessary. A tablespoonful of 

 the powder mixed with a gallon of water and sprinkled on 

 cabbages will destroy the cabbage- worms, though it may be 

 necessary to repeat the application. When the dry powder 

 has been used the success does not seem to have been as 

 good as when applied in water. 



Kerosene Emulsions. — Kerosene oil seems to be particu- 

 larly destructive to insects when brought in contact with 

 them, but it is also injurious to the plants if applied without 

 beino; diluted. It has sometimes been mixed with water and 

 strongly agitated while it was being applied, in order to keep 

 them well mixed. It has now been found that an emulsion 

 of kerosene may be made with soap or milk, which may be 

 diluted with water to such an extent that the mixture Avill 

 not injure the foliage. The most satisfactory formula for 

 the soap emulsion is, kerosene two gallons, water one gallon 

 and common soap one-half a pound, " Heat the solution of 

 soap and add it boiling hot to the kerosene. Churn the mix- 

 ture by means of a force pump and spray nozzle for five or 

 ten minutes. The emulsion, if perfect, forms a cream, which 

 thickens on cooling, and should adhere without oiliness to 

 the surface of glass. Dilute before using, — one part of the 

 emulsion with nine parts of cold water. The above formula 

 gives three gallons of emulsion, and makes, when diluted, 

 thirty gallons of wash. The kerosene and soap mixture, 

 especially when the latter is warmed, forms, upon very 

 moderate agitation, an apparent union ; but the mixture is 

 not stable, and separates on standing or when cooled or di- 

 luted by the addition of water. A proper emulsion of kero- 

 sene is obtained only upon violent agitation. It is formed 

 Dot gradually, but suddenly. The temperature should not 

 be much above blood heat." 



The milk emulsion is made by churning two parts of kero- 

 sene and one part of sour milk with a force pump, keeping 



