102 ANIMAL COMMUNITIES OF STREAMS 



places that support any amount of life. From these logs I have taken 

 hundreds of specimens of small Parnidae, and with them predaceous 

 diving beetles (Dytiscidae) which were found hiding in the cracks, also 

 a few scattered caddis-worms (Hydropsyche). The fauna of the bottom 

 is made up of burrowing and semi-burrowing forms. The little dytiscid 

 (Hydroporus mellitus Lee.) (99c) is characteristic: it has the habit of 

 burying itself in the sand. The bivalved mollusks, especially mussels, 

 are present. From the Deep River (upper course) we have taken 

 nearly a dozen species. The only snail found is a burrowing form also. 

 Animals of such a stream are subject to severe conditions. Many 

 of them burrow. The substratum is very unstable and the logs and 

 parts of trees to which many of them are attached are free to float down- 

 stream with every flood. We know nothing of the reactions of these 

 animals to various stimuli. They are distinctly subjects for investi- 

 gation. 



6. THE SLUGGISH STREAM COMMUNITIES 



(Stations 19, 27, 28, and 29; Tables XVII, XVIII, XX-XXV) 



There are several phases or types of sluggish stream formations. 

 The most important of these are the sluggish or base-level creek, the 

 sluggish river, and the drowned river. These are all illustrated in the 

 Chicago area. 



The sluggish creek type is illustrated by the west branch of the 

 DuPage River and its tributaries; the upper course of the west branch 

 of Hickory Creek, Dune Creek, some parts of the Little Calumet south 

 of Millers, and the Kankakee and some of its tributaries. 



The sluggish rivers are the Upper Fox, the lower St. Joseph, the 

 Grand Calumet, the lower Galien, the lower Black, and others. These 

 constitute a group of streams representative of the sluggish type about 

 the Great Lakes. 



a) Sluggish creek sub-formations (Stations 16, 18). — The west branch 

 of Hickory Creek has been studied in a cursory manner. The fish are 

 a strange mixture of semi-temporary stream and pond forms. The black 

 bullhead (Ameiurus melas) (79) is probably the most characteristic fish. 

 The golden shiner (Abramis crysoleucas) and sunfish (Lepomis cyanellus) 

 are also found. 



Baker (100) studied the upper portion of the east-north Chicago 

 River. He recorded the same species of Mollusca as were taken in the 

 upper part of Hickory Creek. He records also the black bullhead. The 

 insects which he mentions are those commonly found in ponds. This 



