ETTER OF TRANSMITTAL. 
U. S. Department of Agriculture, 
Biological Survey, 
Washington, D. ('.. August 1. 1907. 
Sir: I have the honor to transmit herewith, as Bulletin Xo. 31 of 
the Biological Survey, an economic study of field mice, by David E. 
Lantz. Field mice are so generally distributed throughout the United 
States and at times are so numerous in certain regions that they do 
serious damage to gardens, nurseries, orchards, and forests. The 
several species therefore possess an economic importance quite out of 
proportion to their size. The present bulletin gh~es a concise account 
of their distribution and general habits, the nature of the damage 
they do, together with methods of prevention, the best means of limit- 
ing their increase under ordinary circumstances, and of reducing their 
number's when, by reason of excessive multiplication, the injuries 
they inflict are serious. 
Respectfully. H. W. Hexsiiaw. 
Acting Chief. Biological Surrey. 
Hon. James Wilson. 
Secretary of Agriculture 
