ENTOMOLOGY 373 



As a remedy for mosquitoes, kerosene has proved very effective. 

 It is employed to destroy the larvae of the mosquitoes in their favor- 

 ite breeding places in small pools, still ponds, or stagnant water ; and 

 where such bodies of water are not sources of drinking supply or of 

 value for their fish, especially in the case of temporary pools from 

 rains, which frequently breed very disagreeable local swarms, the 

 use of oil is strongly recommended. The kerosene is applied at the 

 rate of 1 ounce to 15 square feet of water surface. It forms a uni- 

 form film over the surface and destroys all forms of aquatic insect 

 life, including the larvae of the mosquito, and also the adult females 

 coming to the water to deposit their eggs. The application retains 

 its efficiency for several weeks, even with the occurrence of heavy 

 rains. A light grade of fuel oil is preferred for this purpose. The 

 methods of using kerosene as emulsions with soap and milk follow. 

 Kerosene Emulsion (soap formula.} The kerosene-soap emul- 

 sion, following chiefly the Riley-Hubbard formula, has been one of 

 the standard means against scale insects for twenty years. The dis- 

 tillate emulsion generally employed in California for spraying citrus 

 and other trees is substantially the same thing, except that it is made 

 with the California distillate or petroleum oil. Crude petroleum of 

 any kind, as well as the refined product, may also be used in making 

 this emulsion. Emulsions may be applied at any strength with ab- 

 solute confidence that there will be no variation. Where the emul- 

 sion can be prepared wholesale by steam power, its employment is at- 

 tended with no difficulties. In California it is prepared by oil com- 

 panies and sold at very slightly more than the cost of the oil and 

 soap ingredients. It is made after the following formula: 



Petroleum gallons . . 2 



Whale-oil soap (or 1 quart soft soap) pound. . % 



Water (soft) gallon . . 1 



The soap, first finely divided, is dissolved in the water by boiling 

 and immediately added boiling hot, away from the fire, to the oil. 

 The whole mixture is then agitated violently while hot by being 

 pumped back upon itself with a force pump and direct-discharge 

 nozzle throwing a strong stream, preferably one-eighth inch in diam- 

 eter. After from three to five minutes' pumping the emulsion should 

 be perfect, and the mixture will have increased from one-third to 

 one-half in bulk and assume the consistency of cream. Well made, 

 the emulsion will keep indefinitely and should be diluted only as 

 wanted for use. 



In limestone regions, or where the water is very hard, some of 

 the soap will combine with the lime or magnesia in the water, and 

 more or less of the oil will be freed, especially when the emulsion is 

 diluted. Before use, such water should be broken with lye, or rain 

 water should be employed. 



Kerosene Emulsion (milk formula}. This formula is as 

 follows: 



Kerosene gallons. . 2 



Milk (sour) gallon . . 1 



