402 



PRACTICAL HYGIENE 



If either condition be lacking, the disease is not spread. 

 The malarial mosquito {Anopheles} may be distinguished 

 from the harmless, variety (Culex) by the position which 

 it assumes in resting, as shown in Fig. I/O. 



FIG. 170. Mosquitoes in resting position. (From Howard's Mosquitoes?) 

 On left the malarial mosquito {Anopheles} ; on the right the harmless mosquito 

 {Culex). 



Remedies against Mosquitoes. The natural method of 

 preventing the spread of malaria is, of course, the destruc- 

 tion of mosquitoes. This 'is accomplished by draining 

 pools of water where they are likely to breed, and by cov- 

 ering pools of water that cannot be drained with crude 

 petroleum or kerosene. The kerosene, by destroying the 



larvae, prevents the development 

 of the young. In communities 

 where such measures have been 

 diligently carried out, the mos- 

 quito pest has been practically 

 eliminated. Other methods are 

 also under investigation, such as 

 the stocking of shallow bodies of 

 water with varieties of fish that 



feed upon the mosquito larvae. 

 FIG. 171. Stegomyia, T-,- 



the yellow -fever mosquito Yell W Fever.- This scourge 



(after Howard). of the tropics is, like malaria, 



