1922] Fishes in Relation to Mosquito Control 165 



driven to one side or to a corner, leaving the remainder of the water 

 exposed. Furthermore, if oiling is discontinued after it has been ap- 

 plied for some time, the natural enemies of the mosquito have usually 

 either been driven away or killed and thereafter the mosquitoes can 

 reproduce more successfully than before the natural conditions were 

 disturbed. Since fish control is much more permanent in its results 

 and much less expensive, it seems advisable to use fish wherever pos- 

 sible and to apply the oil treatment only where fish cannot be suc- 

 cessfully used. 



Drainage undoubtedlj" deserves first place among the measures of 

 mosquito control because of its permanent character, but it is a recog- 

 nized fact that all water deposits cannot be eliminated and further- 

 more, it is undesirable to eliminate all of them. The cost of drainage 

 usually is high and therefore often prohibitive. Fish control can 

 usually be substituted in part for drainage, and is especially recom- 

 mended for rural sections and for other localities where funds for the 

 more expensive measure are not available. 



A number of species of fishes besides Gamhusia affinis have been 

 recommended for mosquito control, but none has been as extensively 

 used as Gamhusia. Only one other species in the South, viz., Heter- 

 andria formosa, a viviparous species, belonging to the same family 

 as Gamhusia, but of much more limited distribution, ranging from 

 North Carolina to Florida, has given results comparable with those 

 obtained with GamhiLsia. Several species of the genus Fundulus, also 

 belonging to the top minnow family, probably are of limited value. 

 Some of the sunfishes have been mentioned in connection with mos- 

 quito control, but their usefulness in the South is not well established. 

 They certainly are much less efficient than Gamhusia. 



Gamhusia affinis, as already noted, is common almost everywhere 

 throughout the malarious sections of the South. What the conditions 

 without these faithful servants would be is difficult to conceive, but 

 it is quite probable that sections which are prosperous would be in a 

 very backward state and that others would be entirely undeveloped. 

 Doctor H. R. Carter, assistant surgeon general, U. S. Public Health 

 Service, who is well qualified to speak as an authority on the subject, 

 positively asserts* that prosperity is not compatible with the preva- 

 lence of malaria and he declares that no prosperous community exists 



* Public Health Bulletin, U. S. Public Service, No. 105 ; 40. 1920. 



