animal;s and their environment 



293 



decaying material. Click beetles follow, bringing with them the wood- 

 rotting fvmgi and bacteria. The trunk falls, and decay is gradually 

 completed by various microorganisms. In the late stages of decay, 

 spiders, small salamanders, and various other animals may use the log 

 for shelter. 



The longer successions of animals are too complicated for description 

 here. The number of changes and the number of species belonging to the 



i: .{■:.. \-:^:--;-r-y ■'■.■:■.::■ ■'rr^-'r:::-,-.-:::':.-;;.i)-i 



■:,^r?;#^ 



^' . * * * * - * * - • 1 * ■ • . • - ' - . m . . ,.. 





.^ 



Fig. 260. — The filling of a lake wth peat deposits; the succession of land plants is also 

 shown. {After Dachnowski in Bulletin of Geological Survey of Ohio.) 



successive communities are too great for simple summarizing. However, 

 out of later sections of this chapter, in which various aquatic habitats 

 are described, animal successions can be derived if the history of lakes 

 is kept in mind. In general, lakes are being ftUed with washed-in 

 soil and the remains of vegetation growing in them. They are generally 

 converted into swamps or bogs, and finally dry land (Fig. 260). Under 

 these circumstances, the animal communities characteristic of these 

 situations may be placed one after another and together present a rough 

 indication of the animal succession involved. 



