PLACE OF OILING IN ANTI-MOSQUITO WORK 163 



that this mixture does not blow off to one side of a pool so readily 

 as does the film of oil alone. Water gas tar can generally be 

 obtained at a nominal cost from any water gas manufacturing 

 plant. 



Paris green, diluted with a large proportion of inert dust and 

 sown on the breeding-place, much as grain is sown, is reported 

 by Barber and Hayne 1 to be a satisfactory larvicide for Anopheles 

 larvae. It is, however, useless for other kinds of larvae, since 

 they do not feed on the surface. It is reported that 10 cubic 

 centimeters of Paris green will suffice for at least 1,000 square feet 

 of water surface. One part of Paris green to 100 parts of some 

 inert dust, such as road dust, seems to be a favorable mixture. 

 Barber and Hayne report that the minute quantities of Paris 

 green used appear to have no effect upon top minnows or other 

 fish. They suggest, however, that the sower of the poison always 

 keep to the windward side of the dust cloud. 



THE SPRAYER 



The usual — and, for general purposes, the best — method of 

 applying oil to quiet water surfaces is by means of a spray-can, 

 which consists essentially of a container, a pump and a spray 

 nozzle at the end of a short rubber tube. The type which seems 

 to have proven most satisfactory for all-around anti-mosquito 

 work is what is known as the Panama knapsack sprayer. This 

 sprayer holds 5 gallons of oil and fits on the back like a knapsack, 

 the pump being worked over one shoulder and the spray tube 

 being directed by the opposite hand. 



This sprayer will distribute the oil satisfactorily to a distance 

 of 20 to 30 feet from the operator — a valuable consideration in 

 swampy or bushy areas. Another advantage is the fact that the 

 opening of the nozzle can be adjusted, so that heavier oils than 

 those ordinarily used may be employed. The weight is so dis- 

 tributed that the operator should not easily become fatigued. 

 The fact that in walking over rough ground or through bushes, 

 the operator may have both hands free is also important. 



Occasionally, men who oil continuously for several days 

 develop a sore back, caused by leakage of oil from the spray-can. 

 This leakage can generally be prevented by using care in not 

 filling the can too full and by replacing any damaged washers 

 with good ones. 



1 Public Health Reports, Dec. 9, 1921. 



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