FISHES FOR CONTROL OF MOSQUITOES. 3 



The larger aim, therefore, is shifting from extermination to miti- 

 gation and control, especially as it has been found necessary to ex- 

 tend the operations farther from the densely populated centers to 

 suburban and rural districts where sparse population and limited 

 funds forbid expensive methods. This is notably the case in the 

 South, where boards of health and sanitary engineers are grappling 

 with the stupendous malarial problem and are seeking methods of 

 mosquito control less expensive and often more desirable than com- 

 plete drainage. Judging from the experience of the past two or 

 three years one such means has been found in the use of the top 

 minnow. To determine if any similar means capable of wide and 

 general application at small expense exists in the fresh waters of the 

 North this investigation was begun. 



It has long been known that many species of small fishes and 

 predacious insects inhabiting these waters will eat mosquitoes, but 

 little has been done to determine the conditions under which they 

 may be used effectively or the technique of their application to mos- 

 quito control. In the absence of precise biological data the develop- 

 ment of this technique has made little progress. While many mos- 

 quito fighters appreciate the value of fishes, others hold one of three 

 conflicting views — either they are unconvinced that fishes have a 

 place in their particular programs, or they think that almost smy 

 species of small fish once introduced into mosquito-infested waters 

 should automatically destroy the larvae, or they complain that al- 

 though fishes are present they do not eat the mosquitoes living in the 

 same waters. None of these shows a full understanding of the rela- 

 tion that fishes bear to the associated mosquitoes or of the conditions 

 under which they may be effectively utilized in their control. It is 

 the biologist's duty to furnish these data. 



BIOLOGICAL FACTORS IN THE NATURAL CONTROL OF MOSQUITOES. 



Without destroying or greatly altering the habitats in which they 

 live or without killing them, together with associated organisms, by 

 means of poisons or other purely artificial means, how may the con- 

 ditions under which mosquitoes live be so modified as to reduce their 

 numbers to a minimum? Thus stated, the problem obviously be- 

 comes an ecological one. It is a problem of the relation of mos- 

 quitoes to their immediate physical environment or habitat and to 

 their living environment or associated biota. 



The theory of the repression and control of mosquitoes in the in- 

 terest of human health and comfort may be stated as follows : From 

 the point of ^dew of the biologist both man and the mosquito *are 

 successful types which in their spread over the earth have come into 

 conflict. Human dominance requires no discussion. That of the 

 mosquito is evidenced particularly by four facts: First, their nearly 

 cosmopolitan distribution ; second, their great diversity in species and 

 genera ; third, their great range of adaptability to nearly every pos- 

 sible variety of still- water habitat and the complexity and perfection 

 of their specific adaptations to special conditions; and, fourth, their 

 great fecundity and almost inconceivable abundance in places widely 

 separated geographically and of great climatic and physical variety. 

 Anyone who doubts this should read such a book as Howard, Dyar, 

 and Knab's Monograph (1912-1917) or visit the Arctic tundra, the 



