PROGKESS IN BIOLOGICAL INQUIRIES, 1921. 



17 



was that the top minnow, Gamhusia affinis^ was very widely employed 

 as an agent in the control of malaria. A report of observations made 

 by Mr. Hildebrand during this campaign has been published by the 

 Public Health Service.^ 



The latter part of the season was devoted to investigations at Sa- 

 vannah, Ga., where a special effort was made to determine the relative 

 value as eradicators of mosquito larvae of two other American vivipa- 

 rous species of fishes, Hetercmdna formosa and MoUiemsia latipinna, 

 both of which are abundant at Savannah. It was demonstrated that 

 Heterandria formosa is of real value and is well Avorth careful con- 

 sideration wherever it occurs. MoUiemsia latipinna^ on the other 

 hand, appeared to be practically worthless. 



The antimalaria campaigns in the various States were brought to 

 a close early in November, in which month the annual meeting of the 

 National Malaria Committee and the conference of sanitary engi- 

 neers engaged in antimalaria vrork took place in Louisville, Ky., 

 where the outcome of the past season's campaign was reported and 

 discussed. The subject of mosquito control by the use of top min- 

 nows received extended discussion, and the fact was brought out that 

 nearly every sanitary engineer had made use of Gamhusia afjinis as 

 an agent in malaria control with excellent results. The saving of 

 large sums of money was reported, because fish control replaced other 

 methods at much less expense. 



Similar advisory work was done by Mr. Hildebrand in the spring 

 of 1921 before establishing headquarters at Augusta, Ga., for further 

 investigations to determine more fully the conditions of effectiveness 

 in the employment of fish for destruction of disease-bearing mos- 

 quitoes. 



CONDITIONS GOVERNING ABUNDANCE OF MOSQUITO-DESTROYING FISH. 



R. L. Barney and Barry Anson have continued the organization 

 and summarizing of data collected at Mound, La., where investiga- 

 tions of the use of fish for control of mosquito breeding v/ere pre- 

 viously conducted in cooperation with the Bureau of Entomology. 



Reports^ printed outside the Bureau's publications demonstrate 

 the varying seasonal frequency of Gambusia, the mosquito-eating 

 fish; the seasonal variation in the proportions of the sexes and its 

 bearing on the abundance of the species in nature; the effect of en- 

 vironment on the abundance of the species ; and the relation of plants 

 of varying habits of growth to oxygen supply and to the capacity of 

 small ponds to support the top-minnow Gambusia. Further obser- 

 vations have been made on the seasonal abundance of Gambusia. es- 

 pecially in relation to the fecundity of the species. Appropriate con- 

 sideration has been given certain points concerning the anatomj^ of 

 the female reproductive organs of this fish. 



^ Hildebrand, Samuel F. : Top Minnows in Relation to Malaria Control, With Notes on 

 Their Habits and Distribution, Treasury Department, Public Health Bulletin No. 114, 

 May, 1921, 34 p. Washington. 



Barney, R. L., and Anson, B. J. : Relation of Certain Aquatic Plants to Oxygen Supply 

 and to Capacity of Small Ponds to Support the Top-minnow {Oamhusia afflnis). Trans- 

 actions, American Fisheries Society, 1920, pp. 268-278. 



. Abundance of the Mosquito Destroying Top-minnow Gamhusia afpnis. 



Especially in Relation to Male Frequency. Ecology, Vol. II, No. 1, January, 1921, pp. 

 53-69. 



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