United States Department of the Interior, J. A. Krug, Secretary 

 Fish and Wildlife Service, Albert M. Day, Director 



FOREWORD 



During the war and postwar period many new poisons have been and 

 are being developed which, because of their effectiveness in the control 

 of insect, rodent, or plant pests, are likely to be distributed widely over 

 the lands and waters of the United States. DDT is the best known, but 

 several others are being introduced that have similar potentialities for 

 harm. The Fish and Wildlife Service is gravely concerned over the 

 eifects on beneficial fishes and wildlife of such widespread use of toxic 

 agents, and has conducted a variety of investigations during the past 3 

 years to measure the harmful effects and, when possible, to determine 

 procedures or levels of treatment that will reduce them. This circular 

 summarizes the important results to date and contains recommenda- 

 tions that will be of interest and value to individuals and agencies 

 concerned with control of insects and other pests by chemical means. 



Albert M. Day, Director. 



UNITED STATES GOVERNMENT PRINTING OFFICE: 1948 



For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington 25, 



D. C. Price 10 cents each 



