60 AN ECONOMIC STUDY OF FIELD MICE. 



expensive. However, occasionally carbon bisulphid may be used to 

 advantage, especially with pine mice. A little of the liquid is poured 

 upon a piece of rag or other absorbent material and this pushed into 

 the burrow, which at once should be closed with soil to confine the gas. 



MICRO-ORGANISMS. 



The efforts of Loeffler, Danysz, Mereshkowski, and other European 

 bacteriologists to destroy field mice by means of infectious diseases 

 have been partially successful, but as yet no disease appears to have 

 been found that is really contagious. As long, therefore, as infec- 

 tion can be effected only by direct inoculation or through the food, 

 the methods have little, if any, advantages over ordinary poisons. 



The Biological Survey, cooperating with the Bureau of Animal 

 Industry, is engaged in experiments with various micro-organisms 

 for destroying field mice and other rodents, and practical results 

 along these lines may yet be reached. 



RECOMMENDATIONS TO FARMERS. 



When conditions are unusually favorable for an increase of voles, 

 the farmer should put forth all possible efforts to repress them. 

 With cooperation among the farmers of a district serious losses may 

 readily be prevented. The danger lurks outside of cultivated areas 

 and in the swamps, forests, and waste places along fence rows and 

 small brooks that harbor weeds and underbrush. It is b}^ giving at- 

 tention to these and by reducing to a minimum the extent of shelter 

 for mice that the farmer can most successfully protect his crops. 



A second important consideration is the protection of animals and 

 birds that prey upon field mice. The farmer should by all means 

 acquaint himself with the food habits of the various species of wild 

 animals of his vicinity, to the end that he may distinguish friend 

 from foe. Every farmer can do much in his community to help form 

 an enlightened sentiment in favor of beneficial birds, mammals, and 

 other animals. 



PREVENTION OF INJURY TO ORCHARDS AND NURSERIES. 



Injury to orchards and nurseries by field mice may generally be 

 prevented b}" forethought and the exercise of ordinary care. Of 

 first importance, always, is clean tillage. No grass or weeds should 

 be left in or near the nursery. So well is this understood by the ma- 

 jority of experienced nurserymen that by clean tillage they secure 

 practical immunity from the ravages of mice except in winters of 

 deep and long-lying snow. If grass and weeds are destroyed in fence 

 corners and waste lands near the nursery, complete immunity from 

 mice ravages can be depended upon even in winters of deep snow. 



Unfortunately, nurserymen can not control the lands which environ 

 their trees, and when snow falls to a considerable depth prompt 

 measures are sometimes necessary to keep mice from destroying them. 



