782 PATHOGENIC PROTOZOA 



form as the rubber will absorb and covering it over with dry blotting 

 paper. The wide-mouthed catching bottle is uncorked and inverted 

 over the resting mosquito, which is killed by the chloroform. A con- 

 venient trap bottle has been described by La Prince. Below the cork 

 is placed a funnel trap, making it possible to pass from one spot to 

 another without waiting for the chloroform to act upon the mosquito. 



2. The second measure is the prevention of mosquito breeding; 

 this is a large but not a hopeless undertaking, if carried out intelli- 

 gently. In the first place, it is to be remembered that comparatively 

 few mosquitos are disease carriers, and that measures need be directed 

 against them only. It was first shown, for example, by Gorgas, in 

 Havana, that stegomyia could be practically exterminated by doing 

 away with water in artificial containers in the neighborhood of dwell- 

 ings ; this so reduced their numbers that when a case of yellow fever 

 was introduced into a community the disease would not spread. In 

 the same way malaria-carrying mosquitoes may be fought, without 

 regard to the presence of non-disease carriers. An accurate mosquito 

 survey is first made, both by examination of the catch of adults and 

 by a hunt for larvaa in collections of water throughout the district. 

 A puddle or stream is examined by dipping with a white saucer or a 

 long-handled dipper, along the margins; after a little practice it is 

 possible to obtain any larvae which may be present, and to decide by 

 their appearance and behavior whether they are anophelines. It is, 

 of course, unnecessary to waste time and money destroying collections 

 of water free from anophelines. When the breeding places have been 

 located, they may be destroyed by the use of oil or larvacide, by drain- 

 ing or by filling. 



The use of oil and larvacides, while usually a temporary measure, 

 is, nevertheless, of great importance; any light fuel oil may be used 

 by spraying, by mopping the sides of ditches or margins of ponds, or 

 by a drip barrel at the head of a water course. Since in the malarial 

 season the mosquito develops rapidly the oil must be applied regu- 

 larly once a week. 



Wherever possible, the swampy areas and pools must be drained, 

 and for this purpose both agricultural tile and open ditches may be 

 used; in the tropics it is necessary to line the latter with concrete to 

 prevent overgrowth by rank vegetation and to protect the banks 

 against caving. Where, because of the lay of the land, drainage is 

 impracticable the area may be filled, or sometimes flooded, or irrigated 

 with sea water, in which most anophelines do not survive. It is better 



