FLOOD-PLAIN FOREST COMMUNITIES 



201 



bolus marginatus). The white-footed wood-mouse {Peromyscus leucopus 

 noveboracensis Fisch.) nests usually under a stump or a log though some- 

 times slightly under ground or in hollow trees (21). The short-tailed 

 shrew (Blarina brevicauda Say) and the common shrew (Sorex personatus 

 St. Hil.) are common residents. 



In the earlier days (22) the ground stratum was occupied by the 

 larger mammals. The black bear doubtless found the delicate herbace- 

 ous plants desirable at certain times of the year. The Virginia deer 

 occurred here commonly, and the bison and elk invaded the flood-plain 

 forest in going to the rivers to drink. The timber wolf and the common 

 fox, both of which formerly frequented 

 all parts of Illinois, were no doubt also 

 to be found. 



Under fallen logs we find all the 

 animals that are found on the forest 

 floor, and some others also. When a 

 tree first falls to the ground, if it be 

 still solid or living, the animals which 

 attack it are the same as those which 

 attack it when it is standing. If the 

 tree be an oak or a basswood, one of 

 the first of these is the weevil (Eupsalis 

 minuta) (Fig. 156) (155), which bur- 

 rows into the wood. Later the larvae 

 of some of the long-horned beetles are 

 found working under or in the inner 



layers of the bark. These are followed by the Tenebrionidae and the 

 Buprestidae larvae, or flat-headed borers (137). All these tend to let 

 the water between the trunk and bark, which meanwhile has been 

 loosening with every rain, then drying, freezing, and thawing, until it 

 soon becomes quite loose. The space between bark and log is loosely 

 filled with the castings of the many animals that have worked over the 

 outer wood and bark, and with wood and bark that have decayed with- 

 out the aid of these animals. At such a time the space between bark 

 and log becomes the abode of the flattened larvae of Pyrochroidae, 

 centipedes, slugs, ground beetles, and nearly all of the small animals 

 mentioned as belonging to the ground stratum proper. Fallen logs are 

 also the nesting-places of the weasel {Mustela noveboracensis) (142, 143). 



In the autumn we find many hibernating animals under the leaves of 

 the floor of the flood-plain forest. Here we have found water-striders, 



Fig. 156. — An oak borer {Eupsalis 

 minuta Drury): a, larva; b, pupa; 

 c, adult female; d, head of adult 

 male; details of parts are indicated 

 (after Riley). 



