206 



AGRICULTURE ON THE PACIFIC SLOPE 



and if the water is drawn off from below, it will not 

 taste of oil. A roof over the cistern helps to prevent 

 mosquitoes from breeding, because the small plants 



on which they feed cannot 

 grow in the darkness; oil 

 is not always needed in 

 such cases. 



By putting oil on the 

 surface of all standing 

 water, the mosquitoes can 

 be entirely gotten rid of. 

 Swamps should be drained 



FIG. 118. A mosquito which does -, .* , 



not carry malaria. wherever pOSSlble. 



Not all kinds of mosquitoes carry malaria. Figures 117 

 and 118 show the differences between one which carries 

 malaria and another 

 which does not. The 

 figure shows them 

 resting on the ceil- 

 ing. Notice that the 

 one which carries 

 malaria stands with 

 its body perpendicu- 

 lar to the ceiling as 

 if ready to bore into 

 it, while the other has 



its body horizontal. FIG. 119. Wriggler (larva) of a mosquito which 



carries malaria. 



The former seems to 



have three beaks, though really only one, and looks much 



more dangerous than the latter, which shows only one. 



