PLACE OF OILING IN ANTI-MOSQUITO WORK 



161 



usually act differently than oil, as they mix with the water and 

 poison it, killing the larvae rapidly. 



Larvicides also may be used, with the same proviso mentioned 

 above, to treat large wind-swept pools, where the oil film is 

 blown off to one side, before it has time to kill the larvae. They 

 have been used successfully in unpasturecl swamp lands, in 

 fire-barrels, catch-basins, etc. 



THE PANAMA LARVACIDE 



LePrince 1 summarizes the constituents, method of manufacture 

 and application of the Panama larvicide — one of the most 

 popular — as follows: 



"One hundred and fifty gallons of crude carbolic acid, containing not 

 less than 15 per cent of phenols, are heated in an iron tank having a 



Fig. 109. — Treating a fire-barrel with the Panama larvicide. 



steam coil with steam at 50 pounds pressure; 200 pounds of finely 

 crushed and sifted common rosin are dissolved in the boiling acid, and 

 then 30 pounds of caustic soda, dissolved in 6 gallons of water, are 

 added. There is a mechanical stirring-rod attached to the mixing 

 li 



