88 



ECONOMIC ZOOLOGY 



ply mean the overturning of tin cans, tubs, etc. ; even a gutter on a roof 

 that has become clogged with leaves and dirt may breed mosquitoes by 

 the thousand. If the water cannot be led away nor poured out the 

 problem may be handled in other ways; ponds that cannot be drained 

 may be sprayed with kerosene or crude petroleum, about i ounce per 

 15 square feet once a month during the mosquito season; or if this be 

 impracticable or undesirable, the pond may be stocked with minnows 

 or other small fish that will feed upon the larval mosquitoes. These 



FIG. 67. Culex pungens; egg mass, with more enlarged eggs at left; young larvee 

 below. Enlarged. (From Howard, Mosquitoes of the United States.) 



small fish will be much more effective if the sloping banks of the pond be 

 cut away so that the larvae may not escape the fish by going into the 

 very shallow water close to shore. 



Dragon flies are excellent mosquito destroyers, as their larvae 

 eat the larval mosquitoes and the adults catch and eat the adult mos- 

 quitoes. Rain barrels, and cisterns can usually be screened to keep out 

 the adult mosquitoes and this is one of the important proceedings in 

 crusades against the yellow fever mosquitoes in the South. 



In some of the great swamps of the South, the extermination^ .qf 

 mosquitoes is a difficult, if not impossible, task; but in most localities 



