FISHES FOR CONTROL OF MOSQUITOES. 7 



taminated our watercourses, squandered our coal, petroleum, and gas, 

 jeopardized our fisheries, and exterminated much of our larger wild 

 life, and which if persisted in may be expected in time to defeat its 

 own end by expediting human self-destruction. 



In view of the very extensive antimosquito operations now in prog- 

 ress or planned, has not the time arrived to ask if a too exclusive ad- 

 herence to the one thought of killing mosquitoes without regard to 

 the effect of the methods employed upon the associated forms of life 

 may not lead to regrettable consequences ? Should we not seek to sub- 

 stitute, where feasible, ecological methods of control for elimination 

 of the habitat ? 



In beginning the investigation data were collected and observations 

 made upon a wide range of aspects of the subject, and a number of 

 promising leads were discovered. Some of these have been followed 

 far enough to yield material of considerable significance. It very 

 soon became apparent that the problems involved are so numerous 

 and intricate that many workers and much time will be required for 

 their solution. Precise data are required upon so many points that 

 only thoroughgoing, systematic, and long-continued investigations 

 will answer.^ 



For this reason and because of the somewhat insistent demands for 

 advice of immediate applicability attention was early concentrated 

 upon fishes as affording the most effective and most readil}^ utilized 

 of all enemies of mosquitoes, thus confirming the judgment of many 

 previous workers in widely separated parts of the world, but chiefly 

 in the Tropics. The small fishes of the general region of the Dela- 

 ware Valley afforded an abundance of material. The body of this re- 

 port is limited to the results of investigations on several of these 

 fishes, concerning which fairly definite conclusions have been reached. 

 It is hoped that the investigations of certain other species of fishes 

 and of other elements as well may be continued to a point where the 

 results will be worthy of presentation in future reports. It seems 

 probable that the reason why fishes have so far proved more amenable 

 to utilization is chiefly because their habits and needs are better 

 known. Far more attention has been devoted to the culture of fishes 

 than to almost any other group of aquatic animals. If we were as well 

 acquainted with the conditions of multiplication and spread of some 

 of the predacious insects, for example, they mi,ght prove equally 

 efficacious. 



METHODS AND RESULTS OF INVESTIGATIONS ON FISHES. 



The methods of these investigations were at once simple, fairly thor- 

 oughgoing, and comprehensive. After a preliminary examination of 

 many ponds, swamps, streams, etc., at diversified localities in eastern 

 Pennsylvania and New Jersey, during the course of which collections 

 of the fauna and flora and ecological data were made, a number of 

 typical bodies of water, chiefly small ponds, illustrating as wide a 

 range of natural and artificial conditions as possible, were selected 

 for detailed study. Stations were then located on each selected body 

 of water at points where mosquitoes were breeding and at others where 



^ Such an investigation of the anopheline mosquitoes has been in progress at Mound. La., 

 under the .joint auspices of the Bureaus cf Entomology and Fisheries, conducted for the 

 Bureau of Entomology by D. L. Van Dine and for the Bureau of Fisheries by R. L. 

 Barney. 



