LETTER OF TRANSMITTAL. 



U. S. Department of Agriculture, 



Biological Survey, 

 Washington, D. C, August 7, 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 gives 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 

 numbers when, by reason of excessive multiplication, the injuries 

 they inflict are serious. 



Respectfully, H. W. Henshaw, 



Acting Chief, Biological Survey. 

 Hon. James Wilson, 



Secretary of Agriculture. 



