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 Fic. 156.—An oak borer (Hupsalis 
minut) (Eig. 156) (55), which bur ee, hod of aa 
rows into the wood. Later the larvae male; details of parts are indicated 
of some of the long-horned beetles are (after Riley). 
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, 
