328 
MALARIA 
ment unsuitable to the development of 
anopheline mosquitoes rather than attempt¬ 
ing merely to destroy developing larvae. 
Reference is made to the graph showing 
the influence of various anti-mosquito mea¬ 
sures on Lake Wilson. In 1935, owing to 
construction requirements at Wheeler Dam, 
it was essential that the lake be held con¬ 
stantly at maximum elevation throughout 
the mosquito breeding season. Despite the 
fact that about 50,000 gallons of oil and 
41,000 pounds of Paris green dust mixture 
were utilized at a cost of approximately 
$25,000, the mosquito control was unsatis¬ 
factory, as is evidenced by an average count 
of 11 female A. quadrimaculatus per station 
per week and a maximum weekly count of 
46 mosquitoes. The counts were not de¬ 
creased greatly until larvieidal measures 
were supplemented by marginal growth 
removal costing approximately as much as 
the larvicides. In 1936 irregular fluctua¬ 
tion was possible, resulting in some diminu¬ 
tion in the expenditure for larvicides and a 
marked improvement in the station count 
1937 the combination of cyclical fluctuation 
and seasonal recession was employed for the 
first time. The decrease in larvieidal appli¬ 
cation, as well as in station count (less than 
2 mosquitoes per station per week), was 
dramatic. The story for 1938, 1939 and 
1940 likewise confirms the importance of 
water level fluctuation as an anopheline 
mosquito control measure on impounded 
water. 
In the design of the dam and planning 
of an impounded water project, it is impor¬ 
tant to give consideration to the type of 
possible schedule. Each project will have 
to be considered in the light of its primary 
objectives. When storage is the important 
purpose, a slow, continuous drawdown 
throughout the mosquito breeding season 
may provide satisfactory control. If navi¬ 
gation is a major objective, a lower limit 
will exist beyond which the reservoir can¬ 
not be lowered. If reservoirs are con¬ 
structed in tandem on a river, then provi¬ 
sion for fluctuation can be designed and 
built into the projects. In any impound- 
