2 XT. S. BUREAU OF FISHERIES. 



investigation was broadened to cover the whole subject of mos- 

 quito control through natural biological agencies as distinguished 

 from mechanical measures which aim at the complete elimination of 

 breeding areas chiefly through permanent drainage and filling. 



During the three "seasons of 1918, 1919, and 1920 as much time 

 was given to the investigation as other duties would permit. The 

 work as planned was broadlj'^ observational and experimental and 

 covered a territory ]3roviding as great a variety of conditions as pos- 

 sible. The principal experimental work was done on ponds, creeks, 

 and marshes in Philadelphia and Delaware Counties, Pa., and in 

 Palisades Interstate Park in New York. Observations were made 

 and minor experiments were conducted at other points in these and 

 the adjoining States of New Jersey, Delaware, and Maryland. Salt 

 and brackish marshes were studied principally in Cape May County, 

 N. J., and on the Eastern Shore of Maryland; fresh-Avater tidal 

 marshes, on the Delaware Eiver and its tributary creeks in Pennsyl- 

 vania and New Jersey ; and upland waters, consisting of a great va- 

 riety of swamps, swales, ponds, dams, lakes, and streams, especially 

 in Philadelphia, Delaware, Chester, Montgomery, Bucks, and Mon- 

 roe Counties, Pa., Gloucester, Mercer, Essex, and Morris Counties, 

 N. J., and Orange and Rockland Counties, N. Y. 



So many persons were helpful in various ways that it is impracti- 

 cable to name all, but special mention must be made of Mr. and Mrs. 

 George F. Yerger, of Mound, La.; W. V. Becker, in charge of 

 the antimosquito campaign in the Hog Island region; James E. 

 Brooks, engineer of the Essex County (N. J.) Mosquito Extermina- 

 tion Commission; Prof. C. C. Adams, of the New York State Col- 

 lege of Forestry; and Maj. William A. Welch, chief engineer and 

 general manager, and Edward F. Brown, superintendent of Camp 

 Activities, both of the Palisades Interstate Park staff. 



SOME ASPECTS OF THE MOSQUITO PROBLEM. 



In the several decades that have elapsed since Ross, Grassi, Gorgas, 

 and other pioneers worked out the methods of combating the mos- 

 quito hosts of the malarial, yellow fever, and filariasis parasites, 

 which were later applied to mosquitoes in general, a considerable 

 change has become noticeable in the expert s attitude toward the 

 problem. While engineers now work with a confidence and precision 

 born of successful experience, we nevertheless hear much less of mos- 

 quito extermination than in the early days of enthusiasm. The mos- 

 quito problem has grown in magnitude and complexity as knowledge 

 has widened and deepened. As the larger difficulties have been 

 overcome the smaller ones have multiplied. Mosquito extermination 

 has become a futile ideal except for limited metropolitan or other 

 comparatively circumscribed and wealthy areas, where large sums 

 of money for permanent construction and drainage are available. 

 Some of the worst breeding places may be eradicated anywhere, but 

 to completely abolish the moderate breeding which takes place in 

 natural waters over the country generally is beyond our practical 

 resources. It is doubtful if complete mosquito extermination, even 

 were it really desirable, could be effected otherwise than by the elimi- 

 nation of all standing water, and a waterless world would hardly 

 be fit for human habitation. 



