MISCHIEF OF MEADOW-MOUSE 57 
shallow burrows, or supported on grass stems 
or brush-piles above the ground. Sometimes 
they are placed under flat stones or logs or 
under shocks of grain. The structures are so 
slight that a day’s sunshine will dry them out 
after a storm, and yet they are so compact that 
the animals pass the coldest weather snugly 
housed in them under the snow. The young of 
most kinds are born in underground nests and 
are at first hairless and blind. When discov- 
ered in the nest the mother vole slips noise- 
lessly away, sometimes carrying the young at- 
tached to her mamme. 
The breeding-season includes most months 
of the year, except mid-winter in cold latitudes 
and periods of long-continued drought. The 
number of litters in a year thus depends on 
climate, and especially upon the character and 
length of the winter. In temperate latitudes 
in normal seasons from four to six litters are 
produced; but the variation in the same species 
is remarkable, and depends partly upon climate, 
but probably more on the scarcity or abundance 
of food. The period of gestation is about 
twenty days. 
