MIXED PRAIRIE 267 



so there is a whole group of serai stages leading from the newly de- 

 posited alluvium through the meadow stage to the climax of the re- 

 gion. The margins of these rivers are usually occupied by Cicindela 

 re-panda Dej., the somewhat higher ground by C. tranquebarica Herbst, 

 while the moist grasses of the fioodplain support various species of 

 grasshoppers, as follows: 



Acridium acadicum (Scudder) Chortophaga vindijasciata (De S.) 



Orphrdella pelidna (Burm.) Dissosteira Carolina (L.) 



Arphia conspersa (Scudder) Conocephalus fasciatus (De G.) 



Some of these grasshoppers occur in considerable number and de- 

 stroy grasses locally. Belonging to this class are also a number of 

 widely distributed species found in the true prairie and in the moist 

 places in the mixed prairie association. They often increase and ex- 

 tend to planted crops and do striking damage. In the overgrazed 

 grasslands of southern Colorado and New IMexico, such species as 

 Trimeratropis pallidipennis (Burm.) become very abundant. 



River Bottoms. These are sometimes covered with a narrow 

 fringe of cottonwoods, but often no trees occur, as in the valley of the 

 Cimarron in southwestern Kansas. Small dunes and sand fields cover 

 portions of the fioodplain, in which sand sage {Artemisia filifolia) is 

 common. The small skink {Eumeces obsoletus [B. & G.]) and horned 

 toad {Phrynosoma cornutum [Harlan] ) occur in such areas. The 

 tiger beetles {Cicindela scutellaris Say and C. forniosa Say) are asso- 

 ciated with the plants of sandy areas, while C. repanda Dej. and tran- 

 quebarica Herbst dwell on clay soil near streams. 



Steep Banks and Ravines. Steep banks of small ravines support a 

 group of characteristic tiger beetles, such as Cicindela splendida Henz 

 of the eastern part of the plains and C. denverensis Casey of the west- 

 ern. Both are found on the escarpment of the Cimarron. The larvae 

 and adults burrow in the steep banks to the exclusion of level lands. 

 Such ravines also afford convenient places for wolves and coyotes to 

 dig their dens. 



Sandhills. There are numerous extensive sand areas throughout 

 the area of the Great Plains. On the bare and partially bare sands 

 occurs a grouping of animals, including a number of species of tiger 

 beetles such as C. scutellaris Say, formosa Say, venusta Lee, grass- 

 hoppers, a great many burrowing wasps, etc. The western hognosed 

 snake {Heterodon nasicus [B. & G.]) and box tortoise (Fig. 61) are 

 common inhabitants of sand areas. 



Among the sandhills are numerous ponds and lakes with rush- and 

 sedge-covered margins, in which the grasses invade with greater ra- 



