Issued October 28, 190' 



U. S. DEPARTMENT OF AGRICULTURE 



BIOLOGICAL SURVEY— BULLETIN No. 31 



C. HART MERRIAM, Chief 



AN ECONOMIC STUDY OF FIELD MICE 



(GENUS MICROTUS) 



BY 



DAVID E. LANTZ 



Assistant, Biological Survey 



• WASHINGTON 



GOVERNMENT PRINTING OFFICE 



1907 



