76 PREVENTIVE AND REMEDIAL WORK AGAINST MOSQUITOES. 



In his early Catskill Mountains experiments the writer ascertained 

 that about an ounce of kerosene to 15 square feet of surface space 

 is about the right proportion, and that such a film would remain per- 

 sistent for ten days, or slightly longer. He noticed further that even 

 after the iridescent scum had apparently disappeared there was still 

 an odor of kerosene about the water and that adult mosquitoes 

 avoided it. 



In the work done by Mr. H. J. Quayle, near San Francisco" more 

 or less oiling was done upon ponds that could not be drained, and 

 upon standing pools remaining in creek beds during the summer; 

 and some was also done on marsh lands. The oil used was a combi- 

 nation of heavy oil of 18° gravity, and light oil of 34° gravity in the 

 proportion of 4 to 1, respectively. This mixture made an oil that 

 was just thin enough to spray well from an ordinary spray nozzle, 

 and yet was thick enough to withstand very rapid evaporation. 

 It was applied by means of a barrel pump where this could be used, 

 but in the creeks and other situations, which could not be reached 

 by horse and wagon, the ordinary knapsack pump was used. The 

 price of the heavy oil at Burlingame, Cal., was 2 cents a gallon, and 

 of the lighter oil 2J cents a gallon. The former was obtained from 

 the Bakersfield district, while the latter was a product of the Coalinga 

 fields. Mr. Quayle found that the duration of efficiency depended 

 somewhat on the nature of the pool and its exposure to the winds, 

 but in no case could it be counted upon as thoroughly effective after 

 a period of four weeks. 



This period of four weeks brings up the question as to the fre- 

 quency of application of kerosene. The persistence of the oil will 

 undoubtedly vary with the temperature and with the character of 

 the pool — whether exposed to the direct rays of the sun or shaded 

 by trees, or exposed to the wind. Three weeks will probably be a 

 good interval with light fuel oil. The army of occupation in Cuba 

 used its oil every two weeks. 



The application of kerosene to the surface of the water can be 

 made in any one of several different ways. If it is simply poured 

 upon the surface it will spread itself, or will be spread rapidly by 

 light winds. The spra3dng method, either with the barrel pump, or 

 by knapsack pump, or bucket pumps, has been frequently used. 

 The writer watched the oiling of ponds with a spraying pump in a 

 New Jersey town several years ago. The water treated was all in 

 small woodland ponds, and there was a great waste of kerosene. 

 The spray was diffused and became scattered over the vegetation 

 on the borders of the pond, a large share of it being wasted in this 

 way, while the shore vegetation was killed. On small ponds the oil 



oBul. No. 178, Agr. Exp. Sta., Univ. Cal., 1906. 



