Proce:edings Fifth Annuai^ Meeting 37 



conditions of affairs very likely to occur where small quantities 

 of chemical waste are discharged into pools, ponds or streams 

 sufficient to destroy the natural enemies without having any effect 

 upon the mosquito larv^. 



Accumulation of sewage sludge in grassy areas and a con- 

 tinuous flow of raw sewage over them cause intensive breeding 

 places. Generally, where a condition of this kind does exist, the 

 natural enemies of mosquito larvae have been destroyed by the 

 pollution. Water insects and fish will, to a certain extent, keep 

 down mosquito life if the degree of pollution is not too gross, 

 but where the character of the pollution, such as sewage or manu- 

 facturing wastes, either in quantity or quality, is such that it 

 destroys all predatory insects and fish, then pollution becomes a 

 serious matter in mosquito-control work. The varying character 

 of pollution in regard to the quality and quantity has a great 

 influence on the amount of mosquito breeding that can take place 

 in polluted water. The wastes from these sources and the sewage 

 which is discharged into streams constitute a complex pollution 

 which demands a close study. Concerning the pollution, it is 

 necessary to know its origin, character and quantity. The data 

 thus obtained must be submitted to critical analysis to determine 

 in just what way, if any, the pollution affects mosquito-control 

 work. 



An integral part of the work on river pollution and sewage 

 disposal is the study of the character and composition of the 

 wastes discharged from manufacturing establishments. A care- 

 ful and comprehensive study of the individual components which 

 form an offensive manufactured waste often shows that valuable 

 by-products can be obtained by treatment of certain portions of 

 this waste, the recovery of which not only increases the profits 

 of the manufacturer, but also changes the character of the waste 

 so that its discharge into the river ceases to be offensive. 



Where the problem is one of discharging manufacturing waste 

 into isolated pools or ponds that affect mosquito work there is 

 some probability of a solution of the problem being determined, 

 but where the pollution consists of the discharging of raw sewage 

 into rivers and streams or on areas of salt marsh, then the solv- 

 ing of the pollution problem, in so far as it affects mosquito- 



