No. 6 (1917) A NOTE ON TREATMENT OF SWAMPS, ETC. lb/ 



forming as they do dangerous mosquito-breeding grounds. In the 

 interests of public health the Government might compel the 

 owners of plantations to fill up all such pits, but in any case these 

 danger zones should be abolished. 



COCOANUT PLANTATIONS. 



In many cocoanut plantations especially on the West Coast it 

 has been the custom to dig trenches about four feet deep and 

 extending a considerable distance among the trees. The water in 

 these trenches appears to be used largely for soaking cocoanut 

 leaves for purposes of making thatties and consequently becomes 

 very foul. Mosquito larvae can always be found in these places in 

 large numbers. 



It is useless stocking them with fish for the following reasons, 

 viz. : — 



(1) It is impossible for the fish to destroy the larvae owing to 

 the presence of the soaking cocoanut leaves and other debris. 



(2) After a time owing to the foulness of the water the fish 

 become sick and eventually die. 



As these trenches do not serve any very useful purpose they 

 should be filled in. 



STREET DRAINS. 



Badly constructed street drains where water is held up, are 

 always infected with mosquito larvae. The constant cleaning of 

 drains that have a natural earth bottom causes inequalities or 

 depressions which hold water for periods sufficiently long for 

 mosquito larvae to come to maturity. 



If sufficient fall can be obtained, then it is best to build a pucca 

 drain with concrete sides and bottom. If it is impossible to get 

 rid of all water, then kerosine oil should be used freely at least 

 once a week. 



DRAINAGE CHANNELS ON THE SEA COAST. 



All drainage channels which are subject to tidal influence are 

 generally found free of larvae and well stocked with larvae eating 

 fish. But wherever these are obstructed by cross bunds they form 

 dangerous mosquito-breeding grounds. All obstnictions should be 

 removed and the highest reaches possible brought under tidal 

 influence. 



