163 



All observations show that Gamhvsia affinis should prove a great 

 asset in mosquito control. Wherever it was introduced, the mosquito 

 larvae were exterminated in a very short time, unless sufficient pro- 

 tection was offered by submerged leaves or stems of plants. During 

 these experiments, details of which are given, it was noticed that 

 mosquitos may breed in water so strongly acid that it will instantly 

 kill Gamhusia. The number of fish required to effect mosquito control 

 in a given pond varies with the conditions, being appreciably smaller 

 where the water is free from aquatic vegetation and other hiding 

 places for the larvae. The plants that afford most protection, and should 

 therefore be removed, are an aquatic grass, Hydrochloa caroliniensis , 

 a species of Myriophyllum (coon-tail moss) and algae. The latter 

 may be sprayed with oil sufficient to make the masses of them unin- 

 habitable by larvae without killing the fish. Although top minnows 

 are very prolific and multiply rapidly, to ensure their use in mosquito 

 control they must be protected from predaceous enemies such as the 

 large-mouthed black bass. For this purpose shallow hiding places 

 must be provided near the water's edge. 



Other fish that might prove useful in mosquito control include the 

 star-headed minnow, Fimdulus nottii, several species of sunfishes, the 

 roach minnow and the goldfish, the last-named being chiefly suitable for 

 small and artificial waters. 



Herms (W. B,). Occurrence of Malaria and Anopheline Mosquitoes in 



Northern California. — U.S. PublicIIeaUh Repts., Washington, B.C., 

 xxxiv, no. 29, I8th July 1919, pp. 1579-1587. 



Owing to organised effort and widespread individual action the 

 prevalence of malaria in California has been reduced by 60 per cent. 

 during the past 10 years. In 1916 a resolution was passed that the 

 State Board of Health in cooperation with the University of California 

 should undertake a survey of the State. The object of this was to 

 ascertain the specific occurrence and distribution of mosquitos and 

 malaria, to collect accurate information as to breeding places of 

 Anophelines so as to suggest definite and practical measures for their 

 control, and to ensure cooperation amongst the population by giving 

 lectures, distributing literature and carrying out personal work among 

 the ranches. The work was carried out from April to August 1916, 

 covering 7,036 miles in 31 counties of Northern California and reaching 

 an elevation of 8,000 feet in the Sierra Nevada mountains. During 

 1917 the survey was frequently interrupted for inspection of military 

 camps and during 1918 completely suspended owing to the war, but 

 its completion is anticipated during 1919. 



The mosquitos collected include A. qiiadrimaculatus, A. punctipetmis 

 and A. pseudopunctipennis. The first two were found to comprise 

 about 80 per cent, of the total Anophelines. The latter was the 

 predominant species in the coastal and inland coastal valley counties, 

 but seems to be a very slight carrier of malaria, if one at all, as the 

 average annual rate of disease where this species predominated was 

 0-9 to 1-4 per 100,000. 



A. ocddentalis was also found, l)ut is regarded as a melanotic variety 

 of A. quadfimaculalns. - 



