10 



NORTH AMERICAN FAUNA. 



[No. 30. 



enccs of Philadelphia; and Mr. Joseph Grinnell, of the Museum of 

 Vertebrate Zoology, Vj(trk(i]()y, Cal. I am indebted, also, to Mr. Gor- 

 rit S. Miller, jr., and Mr. Ned Hollister for valuable criticism. 



DISTRIBUTION. 



The genus Rfdthrodontorri/i/s is clearly of Austral origin, being most 

 abundant and higlily devciloped in southern Mexico. 



In W(;stern North Amfrrica tlio typical 8ubg(;nus ranges practi- 

 cally tiirougiiout tlie (J[)per and Lowfvr Austral Zones, tlie nortliern 

 limits of its rang(; being iridieat(;d by t\\(\ following localiti(;s where 

 spcicimens have berm taken: Prescott, Wash.; Custer, Mont.; and 

 Fort Clark, N. Dak. East of t}\() Mississjp})i Kivc;r its range is more 

 restricted, and so far as known, tlie genus dors not occur north of the 

 Ohio and Potomac Valleys, tlKi most northerly records being at 

 Cen^do, W. Va., and Falls Church, Va. Soutfiward tlie subgenus 

 Reithrodontonhys rang(!S througli Mexico and Central America to 

 Panama, but it is not known from SoiilJi America. 



The; subgenus Aporodon^ ranges from cr^ntral Mfixico (Jalisco and 

 Vera Cruz) south, througjjout Central Ame.riea and tlience to Ecua- 

 dor, its exact limits being very imperfectly known. 



In the United States th(; gr^nus is confined to the Austral Zones, 

 but in M(;xieo {uid Central Amc^rica ranges from the Tropical at or 

 near sea lev(;l through, all tiui zon(;s to and including the Canadian 

 at timber lin(j. 



HABITS AND ECONOMIC STATUS. 



The harvest mice are preeminently field mice. Practically all the 

 known species live in more or less open grassy situations and are 

 partial to iKsglected fields overgrown with grasses or sedges and to 

 weedy and grassy borders of cultivated tracts. Many species seem 

 to prefer moist situations, and. some (as E. ra/viventris) live exclu- 

 sively in wet marshes, either salt or fresh; others (notably R. albescens 

 and R. raontanus) are found, only in dry, sandy uplands. In the arid 

 West in gcmeral harvest mice are most often taken along the grassy 

 bord(irs of slouglis, small streams, or irrigation ditches; but they may 

 be found in almost any situation, where there is sufficient cover of 

 vegetation to hide them from their enemies. 



(kirtii'm Mexican and Central American species ascend the moun- 

 tains to timber line and live in grassy openings or among brush in 

 the more open parts of the forest. R. soderstromi, of Soutli America, 

 is describcid as living in gardens among climbing plants. 



Some spe(U(is, and perhaps all, construct substantial nests of 

 grasses, often lined with soft materials and placed either on the 



See page r»3. 



