12 The Control of Mosquitoes 



showers are often beneficial, as they remove any 

 Anopheles larvae clinging to banks of ditches or 

 cleared streams. The trade winds assist evapora- 

 tion to a considerable extent, and help to dry the 

 depressions in flat areas that hold water. The 

 soil is of such a character that the trained streams 

 and ditches can be kept to a proper section with 

 less work than is necessary to attain this result 

 at Panama. Washouts and caving of ditch banks 

 did not happen as frequently. 



In many places apparently well fitted for the 

 support of Anopheles larvae, they were absent; 

 yet lived and developed when placed therein as 

 an experiment. The reason why Anopheles eggs 

 are not laid in certain areas apparently in every 

 way similar to those in which larvae are found is 

 yet unexplained. The season of Anopheles pro- 

 duction in Cuba is much shorter and less continu- 

 ous than on the Isthmus. It was largely due to 

 these causes that oiling at irregular intervals gave 

 satisfactory results. Conditions of soil, topo- 

 graphy, and climate there do not favor the rapid 

 and continuous production of mosquitoes as much 

 as in the Canal Zone. 



The drainage connected with the Havana 

 campaign was completed within a year of the time 

 anti-malaria work began, and its maintenance 



