MOSQUITOES 



138 



Methods of extermination. It is fortunate for us in our work 

 of exterminating mosquitoes that they pass the first three 

 stages of life in water, and that the adults must come to water 

 to lay their eggs, that is, mosquitoes are strictly dependent 

 upon suitable breeding waters. In all 

 successful campaigns undesirable pools 

 in which mosquitoes may breed have 

 been drained or filled. Streams and 

 ponds have had their shores cleaned of 

 weeds, brush, and stumps, and have 

 been graded so that pools were not 

 left in which mosquitoes could breed 

 after freshets and storms. Then they 

 have been stocked with fishes which 

 feed upon the young of mosquitoes. All 

 water which was too temporary to drain 

 or too polluted for fishes has been cov- 

 ered with crude petroleum (one ounce 

 to fifteen square feet of surface). This 

 treatment has been repeated as often as 

 wrigglers have appeared. A mosquito 

 can walk on the surface of water but it 

 cannot stand on oil ; hence, as all mos- 

 quitoes come to the near-by water to lay 

 their eggs, they soon perish. Precautions 

 have been taken not to allow water to 

 stand in tubs, barrels, or cisterns with- 

 out being covered insect-tight. 



Through systematic application of 



these methods, Panama, Cuba, New Orleans, and many cities 

 in the north have effectually rid themselves of mosquitoes. 

 The results of these campaigns prove that the extermination 

 of the mosquito from any locality is no longer a matter of 

 doubt or experiment. Through drainage of salt marshes whole 



FIG. 70. Jam bottle and 



tumbler arranged so as 



to secure eggs of a single 



mosquito 



