i:i i-i;i SSK iN ()] I n I i> MICE. 
KCONOMII - I \ I I - < 'I I II I l» MIM 
The foregoing testimony as t<> the ravages of field mice sufficiently 
attests their noxious character. The extent t<> which the} are bene 
ficial to the fanner ma> be stated in iVw word-. I 1 1« * upturning of 
the soil l»\ gophers, ground squirrels, mule-, earthworms, and various 
insects is .-in important part <>f its preparation for man'- use, and 
field mice contribute to the work. In addition, nine diminish the 
number of weeds l>\ eating the seeds and, possibly, occasionally 
devouring the roots. 
The character of the vegetable matter eaten by field mice depends 
entirely upon the environment. 1 1' the animal- live in swamps where 
rushes, sedges, and grasses useless to agriculture abound, their diet 
is confined to these, and the naturalist who investigates their food 
only in such surroundings may fall into the error of concluding that 
they arc not injurious. But field mice at all times -how a decided 
preference for cultivated plant- and grains, if accessible, and in 
winter seek diligently for succulent root- and the green bark of trees, 
REPRESSION OF FIELD MICE— NATURAL AGENCIES. 
In \ lew of their wide distribution and the nature of their habitats, 
the complete extermination of field mice is impossible. It is, how- 
ever, entirely practicable to so reduce their numbers that crops shall 
he safe from serious attack. Before describing the method- which 
the farmer may use to destroy the animal-, it i- important to con- 
sider the natural agencies which aid in their repression. 
(I I MATIC I NFI.IKNU -. 
Climatic conditions so strongly influence the natural increase of 
field mice that an understanding of their relation to such increase is 
important. It has been often noticed that the period- of greatest 
abundance of voles follow one or more open, warm winters succeeded 
by wet summers. If at the same time food — particularly grain — is 
abundant, the most favorable condition- for the increase of the ani- 
mal- are present, and the maximum number of young at a birth, as 
well a> the maximum number of litters, are brought forth. When 
grain is abundant the young of some species are said to begin to 
reproduce when only '2 months old. 
The continuance of favorable condition- for two or more year- is 
Mire to be followed by an enormous increase of field mice, with seri- 
ous injury to crop-. 
Very cold winter- without -now and summers of lone- droughts are 
unfavorable to the increase of field mice. Occasionally a severe 
frost following a heavy downpour of rain destroys nearly all field 
mice over Large areas. 
