REPORT ON MOSQUITOES. 127 



CHAPTER III. 

 DESTRUCTIVE METHODS. 



IvARVICIDES. 



The main effort in tliis investigation was to determine what 

 methods of obtaining- permanent rehef are available ; but it is 

 realized that some places are chronic breeders which, like sewer 

 basins, cannot be abolished, and others must sometimes be dealt 

 with in advance of permanent work to avoid the emergence of 

 a swarm that would otherwise mature and infest the neighbor- 

 hood. In fact, during the beginning of the work in any locality, 

 some means of obtaining immediate results are necessary. 



During the summer of 1902 quite an elaborate series of experi- 

 ments were carried on tO' determine the relative value of a great 

 variety of disinfectants and mosquitocides. Some of these were 

 ordinary commercial products, made and offered without refer- 

 ence to their effect upon mosquito larvae ; others were special 

 preparations sold under a trade name, composition not given or 

 only generally stated. The detailed notes of these experiments 

 were destroyed in the laboratory fire early in 1903, and only the 

 general statements or conclusions can noA\- be given. 



As to the special preparations, except such as are hereafter 

 mentioned, they were all more or less effective, but all of them 

 so expensive in proportion to the results obtained that they may 

 be left out of consideration entirely. 



The soluble Carbolic acid and Ci'csol preparations were all 

 effective at some strength ; but most of them were too expensive 

 for general work and had the disadvantage of permitting pup?e 

 to mature even where the larvae were killed. , 



Permanganate of Potash was very carefully tried, because 

 much had been claimed for it ; but it was found tO' have practi- 

 cally no destructive effect whatever. A solution so concentrated 

 that in a two-quart jar the larvae and pupae were not visible unless 

 close to the glass side, did not kill mature larvae and permitted the 

 development of all pupae. Smaller larvae died in a dav or two, 

 and that was the effect of all strong mixtures. When the per- 

 manganate solution was reduced sO' as to permit seeing through 

 the water in the jars, it produced practicallv no effect. at all. 

 The details are lacking, but the conclusion is positivelv remem- 

 bered. 



