274 



AGRICULTURE 



Knowing how the disease is spread, it becomes possible 

 to prevent it entirely. The malarial regions are simply 

 those where the malarial mosquitoes are abundant. It 

 has been positively proved that it is possible for people 

 to live even in the worst of such regions and yet to keep 

 entirely well by guarding against being bitten by the mos- 

 quitoes. Their bites can be escaped, for the malarial 

 mosquitoes are active only between sunset and sunrise. 

 The thorough screening of the 

 houses is the most certain means 

 of preventing the spread of the 

 disease. In addition the draining 

 or filling of the standing water 

 pools in which the mosquitoes 

 breed should be done. Small fish 

 live on mosquito wigglers and, 

 hence, fish should be kept in 

 ponds that cannot be drained or 

 filled. 



How to know the malarial mos- 

 quitoes. Whether we desire to de- 

 stroy or to avoid these mosquitoes, 

 we should know how to tell them from harmless kinds and 

 also be able to tell the larvae or wigglers, in their breeding 

 places. All of the mosquitoes that are concerned in 

 spreading this disease belong to a single group and are 

 closely related. The adults are rather long-legged as 

 compared with other kinds ; when at rest, they stand 

 with their bodies pointing head first to the surface 

 to which they are clinging (Fig. 176). Other mosquitoes 



FIG. 176 MALARIAL MOS- 

 QUITO BELOW; COMMON 

 MOSQUITO ABOVE 



