276 THE NORTH AMERICAN GRASSLAND 



Serai Stages. The most important serai habitats due to recent 

 glaciation are ponds and marshes. The temporary ones are usually 

 dominated by Spartina, though in many cases rank forbs are also pres- 

 ent. There is nothing especially characteristic about prairie ponds so 

 long as they are permanent. In the later stages, however, they differ 

 from forest ponds in the lack of shrubs and trees in the margin 

 (Shackleford, 1929) . Prairie marshes, especially those dry in autumn, 

 were formerly extensive, particularly in Illinois and Indiana, and were 

 the favorite haunts of numerous insects and vertebrates, such as the 

 massasauga or swamp rattlesnake, and the bobolink and other swamp 

 birds. 



Sand areas were important but were marked by more xeric condi- 

 tions and hence supported the plains insects and reptiles adapted to 

 drier regions. 



Contacts. The most important contact is with the deciduous forest, 

 which as a proclimax extends westward in the river valleys of the true 

 prairie. In it are found the Virginia deer, black bear, gray squirrel, 

 the timber rattler, and numerous w^ood-boring and tree-dependent in- 

 sects, among which the green tiger beetle {Cicindela sexguttata Fabr.) 

 is a conspicuous example. The edges of these W'Oodland areas are 

 fringed about with low trees such as hawthorn and wild plum, and 

 outside these are such shrubs as sumac, dogwood, snowberry and coral- 

 berry, and accompanying forbs. Most of this prairie has some of this 

 forest and forest edge at intervals of a score or so of miles. These 

 woodlands also supported elk, which commonly grazed on the prairie 

 grasses, but browsed in the woodland, particularly in the winter. Even 

 the Virginia deer was not excluded from the forest edge, although, 

 being a browser, it perhaps did not take food in quantity from the 

 grassland. 



Such prairie animals as the coyote {Canis latrans Say) sometimes 

 entered the w^ooded areas, and the gray or Franklin ground squirrel 

 usually held relatively close to them, as did the jumping mouse of the 

 region. A great number of song birds nested especially in the shrubby 

 margins of these forests, and other birds such as the crow lived or 

 nested in the woodland and sought food on the prairie; various hawks 

 and owls belong in the main to this class. There were also numerous 

 insects usually limited to such forest edges. 



The contact with the aspen belt which lies between the coniferous 

 forest and the grassland in Canada is particularly significant in bring- 

 ing out the relations of animals (Bird, 1927, 1930). The badger and 

 other burrowing animals, in constructing dens near the edges of the 

 woodland, broke the sod and made possible the establishment of snow- 



