544 Introduction to the Study of Science 



tion is being waged. The various methods employed in bringing 

 about their extermination are based upon exact knowledge of 

 their life history and habits. This knowledge makes it possible 

 to devise simple and effective measures. 



The fact that all mosquito larvae are aquatic and direct 

 air-breathers points the way clearly to their destruction. Any 

 means that prevents their getting to the air insures their death. 

 A thin skin of kerosene is used for this purpose. The oil- 

 covered water is destructive not only of the larvae, but also of 

 mosquitoes alighting on it. If mosquitoes find no water in 

 which they can deposit their eggs, they lay them in grass or 

 leaves where destruction is almost inevitable. 



Drainage of marshes, stocking ponds with fish that prey upon 

 mosquitoes in any stage of development, covering small pools, 

 ponds, and the like with some viscous substance as kerosene, 

 have all proven to be effective in destroying the mosquito. 

 Among the more immediate measures which every one should 

 take is to remove or destroy all breeding places due to careless- 

 ness. Old cans, bottles, troughs, and any receptacle that can 

 hold dirty water should not be allowed to accumulate in corners 

 or alleys, nor should garbage piles be permitted ; for in all of 

 these mosquitoes may deposit their eggs. Water tanks, barrels, 

 and drain pipes need constant care for sanitary reasons, and they 

 should be screened also to prevent mosquitoes and other insects 

 from entering them. 



When mosquitoes are prevalent in spite of such preventive 

 measures, they should be kept out of houses and other buildings 

 by screens. Certain preparations are useful, moreover, for 

 those exposed in outdoor duties to the attack of the pests. 

 Among such oil of eucalyptus either by itself or in mixture with 

 other substances may be applied to the face, hands, and ankles. 

 Oil of citronella is commonly used and is less disagreeable than 

 some other applications. A more effective application is a 

 mixture of two parts of oil of citronella, two parts of spirits of 

 camphor, and one part of oil of cedar. 



