70 The Control of Mosquitoes 



found in that part of a body of water affected by 

 it, although they are found in other parts of the 

 same body of water to which this substance has 

 not extended. 



PROPAGATION AREAS CREATED BY MAN 



It is surprising how many mosquitoes are 

 unnecessarily brought into existence by people 

 who are aware that the construction work they are 

 doing will cause Anopheles to multiply. They do 

 this even when it would cost no more to arrange 

 for proper drainage. Borrow pits or excavations 

 are made where they tap seepage water planes, 

 and are sometimes left to collect water, in places 

 where they cannot be drained. 



River channels are blocked up near settlements, 

 flooding hundreds of acres with shallow water. 

 Culverts are situated in a way that causes ponds 

 to be formed, and streams and ditches to fill with 

 silt. They are often entirely closed up, and the 

 water allowed to spread where it will. Such condi- 

 tions have been created by engineers who knew 

 the ensuing results, but were apparently in no-way 

 interested providing they did not suffer personally 

 or financially. 



The additional cost of controlling malaria in 

 these localities has been enormous and made the 



