PLACE OF OILING IN ANTI-MOSQUITO WORK 



165 



be developed with some of these pumps, so that a stream of oil 

 may be thrown 50 feet or more. 



While such spray-pumps are very useful for oiling parts of 

 ponds, lakes, etc., or edges of rivers and streams or pools in open, 

 accessible territory, they lack the portability of the knapsack 

 sprayer and usually are of but little value in swamp work or in 

 areas where the terrain is rough or timbered. 



For limited areas and for use about homes, etc., the oil may be 

 distributed by means of a garden watering-pot or a small insecti- 

 cide sprayer. An oil-soaked broom may be stirred into many 

 small pools with good effect. 



DRIP CANS 



For flowing ditches or streams, "drip-cans" have proven very 

 satisfactory. These may be adapted to either continuous or 

 intermittent application, as the case may require. 



Drip-cans consist essentially of 

 a receptacle for oil, arranged in 

 such a manner that a small quan- 

 tity of the fluid drips from it into 

 the water. This is wafted along 

 by the current and bathes both 

 banks, also, if the stream is in 

 good condition — that is, free from 

 obstructions and vegetation — 

 covering pools and backwaters, 

 where breeding is most likely to 

 take place. 



Drip-cans should be suspend- 

 ed three or four feet above the 

 stream. If heavy oil is used, this 

 elevation may profitably be in- 

 creased, since the impact of the 

 drops of oil on the water breaks 

 them up and accelerates forma- 

 tion of the film. The precaution 

 should be taken of securing the drip-can in such manner that it 

 will not be swept away by high water. 



In making the drip-can, the outlet ordinarily should be placed 

 an inch or so from the bottom of the can, so that any settleable 

 solids in the oil will not cover up the hole. The outlet should be 



Fig. 



112.— Sketch of 

 drip-can. 



easily-made 



