260 THE NORTH AMERICAN GRASSLAND 



with their several varieties are found throughout the grassland as 

 very important coactors, feeding on rodents. Among the insects 

 (Hayes 1927), the Orthoptera are the outstanding group, especially 

 the various grasshoppers. Kansas exhibits 118 genera and 301 species, 

 of which 59 range eastward (Hebard, 1931). New Jersey shows but 

 152 species of orthoptera in 60 genera (Smith, 1909), several of them 

 suspected of having extended their range into the deciduous forest 

 area since clearing. There are approximately 240 more species of the 

 grassland orthopterans than of those in New Jersey. This is in spite 

 of the fact that the latter has a greater diversity of habitat. The 

 genus ]\Ielanoplus comprises 58 species in Kansas, while only 10 are 

 recorded from New Jersey, 8 of which are common to the two states; 

 Trimcrotropus has 23 species in Kansas and only 1 in New Jersey. 

 The Hcmiptera are well represented, and among the Homoptera, the 

 genus Flexamia is a characteristic grassland genus. 



MIXED PRAIRIE 



Nature and Extent. The name of this association is drawn from its 

 two most characteristic features. The first and more obvious is the 

 mixture of mid and short grasses, though this is an outcome of the sec- 

 ond, namely, a mingling of dominants from very different sources. 

 The mid grasses are circumpolar in origin, the short grasses south- 

 western, and the tall grasses of the postclimax southern or subtropical 

 as a rule. Ecologically speaking, several species of Carex are reck- 

 oned among the short grasses, though by contrast these are northern 

 in derivation. In addition, the central position of this unit in the for- 

 mation has led to much interchange of influents with the other asso- 

 ciations, of which it is regarded as the parental type (cf. Visher, 1916) 

 (Figs. 58-59). 



The mixed prairie covers a much larger area than any other unit of 

 the grassland, extending from central Alberta to Texas and thence 

 westward to the Colorado Valley. It includes the prairie districts 

 of Alberta, Saskatchewan, western Manitoba, the western two-thirds of 

 North and South Dakota, the western half of Nebraska, Kansas and 

 Oklahoma, northwest Texas, northern New Mexico and Arizona, east- 

 ern Utah, Wyoming, and INIontana. From Canada to northern Texas, 

 it lies in contact with the true prairie to the east through the medium 

 of a broad ecotone. It meets the coastal prairie in north-central Texas 

 and the Palouse grassland in western Montana, eastern Idaho, and 

 northern Utah. The ecotone between it and the desert plains extends 

 from central-west Texas through central New Mexico and Arizona, 



