near relatives of the deer mice, but are easily distinguished from the 

 latter by their heavy bodies, short tails and usually paler colors. They are 

 dwellers in the open country, never, to the best of my knowledge, found 

 in underbrush or about rocky places. They live largely, if not entirely, 

 in holes in the ground, sometimes in holes abandoned by other animals, 

 such as prairie dogs, for I have taken them at the old burrows; and they 

 may dig homes for themselves, as they have good, strong fore paws and 

 claws and are often taken at small holes on the prairie. As might be in- 

 ferred from the names, they eat animal as well as vegetable food, destroy 

 a good many insects such as grasshoppers and beetles, and are called 

 "Scorpion Mice" because they eat scorpions when found. One which I 

 kept in confinement for a short time preferred raw meat to any of the 

 vegetable foods I offered it. Their animal diet causes them to decompose 

 much more rapidly after death than mice which feed mainly on vegetable 

 matter. They have a considerable range in altitude, being found from 

 the lowest elevations in the state to as high as 8,500 feet in North Park. 



The species are all bicolored, the under parts and feet being white, 

 while the color of the upper parts in adults of course varies in different 

 species, but is generally some tawny color, occasionally quite reddish in 

 individuals. The young, as in the case of the deer mice, are blue or mouse 

 gray in color, gaining the adult colors with maturity. They breed in spring 

 and summer, having from three to six young in a litter, four probably 

 being the average number. 



The body is stout and heavily built, and while the total length is 

 about the same as that of the deer mice inhabiting the same regions, the 

 Grasshopper Mice look larger because of the proportionately shorter tail. 

 The total length is six inches or a trifle less, and the tail 1.7 inches. 



In Colorado we have two species or rather subspecies of these ani- 

 mals, Seton's Grasshopper Mouse, Onychomys leucogaster arcticeps, and the 

 Black-browed Grasshopper Mouse, Onychomys leucogaster melanophrys, the 

 two having separate distributions, but together inhabiting most of the open 

 prairie and park country of the state, and, as before stated, attaining an 

 altitude of 8,500 feet in North Park. 



HARVEST MICE. 



The Harvest Mice, whose generic name is Rheithrodontomys, are small 

 animals inhabiting in North America the two Sonoran zones. East of the 

 Mississippi river they do not occur north of the Ohio and Potomac valleys, 

 whereas in the western United States they range into North Dakota, Mon- 

 tana and Washington, and southward through Mexico and Central America 

 to Panama. In Mexico and Central America the genus ranges from the 

 tropical zone at or near sea level through all the zones to and including 

 the Canadian at timberline. Howell, in a recent revision of the genus, 

 recognizes fifty-eight forms, of which four are found in Colorado. 



The members of this genus can always be recognized by the upper 

 incisors each having a longitudinal groove. This groove is very fine and 

 one sometimes has to look quite closely to find it. While they have a 

 superficial resemblance to the deer mice, they are smaller in size, with 

 proportionately longer tails, which are slender, scaly, and thinly haired. 

 The ears are prominent. 



Our Harvest Mice are dwellers in the open, preferring places over- 

 grown with grass or weeds. One of the Colorado species, the Pallid Harvest 

 Mouse, is found only in dry, sandy uplands. In the dry western regions 

 these mice in general are apt to frequent the grassy borders of sloughs, 

 small streams, and irrigation ditches. The nests are built of grass, lined 

 with soft materials, and placed either on the ground, or above it in bushes 



11 



