192 Fretp Museum or Natura History — Zoétocy, Vot. XI. 
posed of soft grass, etc.; it is spherical, and the small internal cavity 
is entered through a narrow opening on one side. In cultivated fields 
the burrows are frequently dug at the roots of fruit-trees, the bark of 
which is often gnawed, sometimes causing great injury. In nurseries, 
fruit-trees are often taken up and ‘heeled in’; that is, laid down close 
together, with the roots placed in a trench, and then covered in such 
manner that they are kept safely in a very small space, and can be 
readily pulled out when desired. The loose earth among the roots 
of these offers an inviting habitation to the mice; and, in nurseries in- 
fested by them, they will be found burrowing in almost every lot of 
trees thus buried, where they feed upon the bark of the roots, and thus 
cause serious damage. In the fall, they are often found in corn-shocks, 
making a nest among the stalks, though they do not so often burrow 
under these as the arvicole. But, during winter, they may be tracked 
in corn-fields from their burrows to the neighboring corn-shocks, which 
they have visited for food. In spring, the young are always produced 
in burrows. During the summer, however, they occasionally are 
observed in nests, under bits of wood or bunches of hay, on the surface 
of the ground. In autumn, I have found nests of the young in small 
burrows only a few inches below the surface, or under an inverted sod. 
I have never observed more than one pair of adults occupying the same 
burrow; and, unlike the Mus leucopus, this species never appears to 
be gregarious. 
“This mouse must be very prolific. I have found the young in 
March and April, and observed two females, each with five young, 
apparently but a few days old, about the tenth of November, while 
they are found in every intervening month. In nearly every instance 
within my observation the number of young produced at a birth has 
been five. I once found six, and have at times, though rarely, seen 
three or four. The young are found attached to the teats, as in the 
species last described; and a female was seen to carry five for several 
rods in this way, jumping along rapidly despite their weight. As 
soon as they are able to take care of themselves, the young leave the 
mother. In summer, I have several times found one apparently but 
a few weeks old, living alone in a nest made by himself. In spring, I 
have always found the old male living with the female and young; but 
during the summer, I have sometimes observed the male leading a 
solitary life, and the females and young in burrows by themselves. 
The food of this mouse, on the prairies, appears to be herbaceous plants, 
with their seeds; but I have been unable to see that it ever digs for 
roots. It is interesting. to observe that this, like the Mus leucopus, 
seeks its food on the top of the ground, running on the snow in winter 
