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Illinois Natural History Survey Circular 49 



larval cases or in specially constructed cocoons in the water. When 

 mature, the pupae escape, swim to the surface, and crawl up on plant 

 stems ; the adults emerge from the pupal skins. These insects abound 

 in the waters of the Dead River, fig. 15 ; three species of them have 

 been found in no other area in Illinois. 



SPREAD OF TEMPERATE DECIDUOUS LIFE 

 Although the Dunesland life contains many northern species, the 

 great bulk of it comprises species typical of the temperate deciduous 

 forests. These species include several kinds of willows, grasses, 

 sedges, the black oak, and many other plants. To this list belong 

 also a large number of spiders, insects, and other animals, fig. 16. 

 All these forms of life spread into the Dunesland from areas to the 

 south; they probably arrived by a variety of routes and at different 

 times. Some of the species may have spread into the Dunesland from 



Fig. 16. — Two animals typical of the temperate deciduous forest biome; both occur in the 

 Dunesland. Above, the eastern tiger salamander, Ambystoma tigrinum tigrinum. Below, the northern 

 water snake, Natrix sipedon sipedon. 



