Proceedings of Eighth Annual Meeting 119 



of experimenting with several grades, until one suiting local re- 

 quirements is found. The distillates of crude petroleum, kerosene 

 and fuel oil, are most commonly used in mosquito control in New 

 Jersey. 



The use of kerosene, although very effective — inasmuch as it 

 makes a thin film and spreads quickly — is impractical in county- 

 wide operations, due to the following disadvantages ; first, rapid 

 evaporation ; second, excessive waste, owing to the difficulty of see- 

 ing the oil film on the surface of the water ; and third, high cost. 



The heavy oils, those having a mixed or asphalt base, while cheap- 

 est in first cost, do not spread as much or as rapidly as the lighter 

 oils. They are often too thick or too heavy for use in the sprays 

 and more oil must be used per unit of area to secure a killing film. 

 The heavy oils, however, may be treated with kerosene or larvicide, 

 to increase their spreading qualities, but such treatment makes for 

 increased costs. 



Gasolene has been used, but it evaporates rapidly and completely 

 and owing to its excessive cost, its universal use is impractical and 

 limited to certain production areas on private property, where dis- 

 figuration by the use of oil would meet with opposition on the part 

 of property owners. 



Fuel oil is generally used in New Jersey. The grades available 

 vary considerably due to the locality from which the crude product 

 is obtained and the method of refinement, and range from light 

 yellows to almost black. The light oils evaporate quickly and the 

 black oils film too slowly. A satisfactory oil should film and spread 

 rapidly, withstand evaporation and be comparatively cheap. 



Petroleum may be applied in various ways. In New Jersey the 

 Standard Barrel Spray Pump is most commonly used and found to 

 be very satisfactory. The use of sprinkler cans, oils drips, subaque- 

 ous bubblers, oil-soaked waste and oil-soaked sawdust, either in con- 

 nection with the spray or separately, depends on the various types 

 of production areas. Each method of application has its advantages, 

 as well as disadvantages, which makes its use practical or im- 

 practical. This is a problem that must be solved by those in charge 

 of operations, based on a full knowledge of local conditions. It is 

 generally a combination or a modification of several methods that 

 secures the best results. 



The efifectiveness of petroleum as a larvicide depends on a per- 

 fect film, which must remain unbroken for several hours to insure 

 the reduction or destruction of the larvae under it. In actual field 



