272 A NATURALIST IN THE GREAT LAKES REGION 



favorable hunting ground. Succinea avara and S. retusa are 

 found crawling over the wet ground or on the plants. These 

 snails are very widely distributed in wet and marshy situations. 

 This zone may be called the giant ragweed zone from the plant 

 standpoint, and the Succinea zone on its animal side. 



Then comes a zone of willows, chiefly Salix nigra and S. longi- 

 folia. The trees nearest the stream are usually small ones, the 



FIG. 415. Flood plain of river with vines draped on trees 



larger ones standing farther back. With these larger willows 

 are the young white ash, elms, and soft maples that characterize 

 the beginning of the flood plain forest proper. When these willows 

 are in blossom in the spring there are present many flies, bees, 

 and pollen-loving beetles like the bumble beetle. Later the 

 conspicuous animal life is the large number of moth and butterfly 

 larvae that feed on the willow. Mourning cloak and viceroy 

 larvae are often found in swarms, while the larvae of Cecropia 

 are usually abundant and conspicuous on account of their large 

 size during the fall. Those of the Sweetheart and Bride are less 



