Page:Popular Science Monthly Volume 89.djvu/381

 Exterminating Mosquitoes

��NEXT to ilraining, the best way to abolish mosquito breeding places is to treat the water so as to kill the mosquito larvae and while main- substances have been tried for this purpose, nothinij has given such good results as petroleum, according to ex- l)erts of the United States Department of Agriculture. Common kerosene of low grade is most satisfactory as regards I ihciency and price.

It has been found that spraying with a portable pump is the best way to use the oil. Small jionds, however, can be sprinkled out of an ordinary watering- pot with a rose nozzle, or for that matter pouring it out of a dipper or cup will be satisfactory. In larger ponds pumps with a straight nozzle may • be used. A straight stream will sink and then rise and the oil will spread until the whole surface of the water can be covered without waste.

In choosing the grtide of oil to be used

two factors must be considered; it

should spread rapidly and should not

evaporate too quickh".

^M^^ Heavier grades of oil

^^^^B will be apt to gather in

��spots and the coaling will be neces- sarily thick. It has been found that one ounce of kerosene is sufficient to cover fifteen scpiare feet of surface, and in the absence of wind, such a film will remain persistent for ten days. Even after the iridescent scum apparently disappears there is still an odor of kerosene about the water. A mixture of crude oil and kerosene has lieen found to be effective in killing mosquito larvae. It has one very decided advantage over pure kero- sene which is that it does not evaporate so quicklv'.

Special attention should be paid to little pockets of water that form around the edges of ponds, for it is in such places where the water is not disturbed by wind or otherwise that the larvae breed in greatest numbers. Larvae do not Ijreed in open stretches of water where the surface is rippled by the wind.

In the fight against the mosquito in Panama, the government experts found that a larvicide composed of carbolic acid, rosin and caustic soda was very effective and thousands of gallons of it were used. Crude oil was employed in streams having a fair velocity.

���Covering the Surfaces of Ponds and Other Breeding Places with Petroleum, According to Experts of the Department of Agriculture. Is the Best Move Against Mosquito Larvae. The Illustration Shows a Pond Being Sprinkled with Petroleum from a Portable Pump

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