8o The Control of Mosquitoes 



The commercial kresol preparations on the market 

 have similar qualities but are more expensive than 

 the product we use. If these aids are not at hand, 

 fairly good results may be obtained in water 

 of less than a foot deep by thoroughly stirring 

 up the mud below the water. This generally 

 makes the larvae come to the surface in a short 

 time. In shallow water where a large number of 

 places must be examined in a short time, inspection 

 is made by walking in the water and stirring with 

 the foot. If grass or debris is present it must be 

 pushed or held back to leave a clear area for 

 observation. Where the water has almost dis- 

 appeared from depressions, or only soft mud 

 remains, samples may be washed in clear water to 

 determine the presence of larvae. The observer 

 should walk along the beds of streams, or the edges 

 of ditches or ponds, and examine all places that 

 appear favorable, including floating debris on the 

 surface of deep water. In ponds and lagoons in 

 which tall grass grows examination should be made 

 by boat, or if none is available the inspector must 

 wade out until he knows the condition of all places 

 that may harbor larvaj. It must always be re- 

 membered that the productive portions of a rela- 

 tively large area may be limited to certain small 

 ones, either in fresh or brackish water marshes. 



