'IMII') I'liAIlxMK MOISK. 511 



o:uilty also. l)ut T have caught the prairie voh' near freshly cut 

 stems when none of the other species were to be found in the local- 

 ity. Wild seeds and berries are (>aten also, but the principal food 

 of this species is grass. 



The nest is of dry grass and is placed under ground or under 

 a protecting log or rock. One that I found was in a little depres- 

 sion under a discarded railroad tie lying on the side of an embank- 

 ment. At the time of discovery, about 4 p. m. on April 11, the 

 mother was not at hoin(\ and I carefully replaced the tie over the 

 nest containing three hairless and blind young. Early the next 

 morning the old mouse was again absent but about ten o'clock I 

 found her nursing her offspring. She began to run with the young 

 still clinging to her teats, but the whole family was captured. They 

 were confined in a roomy wire cage with plenty of dry grass and 

 cotton for a nest and fresh grass, bread and water for food. Never- 

 theless, the next morning the cage contained only the mother; she 

 had eaten her children. The old mouse lived only two days longer. 

 She showed a surprising ability to climb, not only going up the 

 sides of the cage, but creeping, fly-like, across its wire top with 

 her claws hooked in the meshes of the wire and her body hanging 

 downward. 



The breeding habits are very much like those of Microtus penn- 

 sylvamcus. I have caught young almost four inches in length on 

 April 2d; they must have been born about the first of March. 

 Pregnant females have also been found in September and the breed- 

 ing season evidently includes all of the summer months, though I 

 am positive that they do not. as a rule, breed between October and 

 February. Sometimes they mate as soon as the litter of young is 

 born. The period of gestation is short, probably not over three 

 weeks. I have never found more than four young in any litter. 

 Two and three at a birth are quite usual. Miller states that the 

 number of mammae is four, but he evidently erred, for Bailey gives 

 the number as six, and all that I have examined when the mammae 

 were in condition to be distinctly seen, had six. This would seem 

 to indicate that more than four young are sometimes produced at 

 a time. 



Economic status. — In the southern part of the State, at least, 

 this species is more destructive to crops than the preceding one, 

 but less so than the following; the white-footed mouse or the house 

 mouse. Its work is confined chiefly to places that can be easily 

 reached from fields or fence rows that are overgrown with grass, 

 weeds and bushes. Therefore, a very effective way of ridding a 



