ENEMIES OF PLANTS. 303 



penetrating the breathing pores and suffocating 

 the insect or by corroding the body. 



(i) Kerosene Emulsion. Of the contact in- 

 secticides, kerosene, emulsion is one almost 

 universally used by Agricultural Experiment 

 Stations. 



The emulsion formula : 



Soap l /t pound 



Soft water i gallon 



Kerosene 2 gallons 



The best soap for this purpose is whale-oil 

 soap, though ordinary soft soap or hard soap 

 will answer. The soap should be shaved into 

 the water and thoroughly dissolved by heating. 

 When boiling hot, pour the solution into the 

 kerosene, away from the fire, and churn vigor- 

 ously about ten minutes by pumping the liquid 

 back and forth with a force-pump until it resem- 

 bles buttermilk. The emulsifying will increase 

 the bulk about one-third; hence, the emulsion 

 should not be prepared in too small a vessel. 



If tightly sealed, this stock solution will keep 

 for some time. When wanted, dilute with ten 

 to twenty parts of water. If too strong, the 

 kerosene will injure tender foliage. Apply with 

 a spray-pump (Fig. 102) to the infested plants. 

 The emulsion must come in contact with the 

 body of the insect, so that the kerosene may 

 penetrate the breathing pores and suffocate the 



