Anopheles Propagation Areas 71 



cost of the anti-malaria campaign very much 

 higher than it would have been had sufficient 

 authority been given to the sanitary officials to 

 prevent the unnecessary formation of hundreds of 

 acres of artificially created mosquito-producing 

 areas, with the corresponding attendant costs for 

 their control, and for the care of sick laborers 

 affected. 



DITCHES 



Even where anti-malaria work is being per- 

 formed, parts of ditches or pools not kept in proper 

 condition will harbor larvae. Any obstruction or 

 change of conditions that interferes with the flow of 

 water in a ditch, and any condition that brings 

 about the breaking of the continuity of the oil film 

 may attract mosquitoes. Production is increased if 

 the amount of water flowing in the ditch decreases. 



Where the matted algae breaks up and some 

 portions of it sink, the direction of the small 

 current in the ditch bed changes frequently, and 

 increases the number of places and the extent of 

 area where larvee may be found. Conditions are 

 aggravated if cattle have access to the ditch. If 

 treatment is neglected or faulty inspection is 

 made, the ditch becomes a menace and produces 

 large numbers of mosquitoes daily. The flatter the 



