Table 3 



Average Density of Benthlc Organisms (Number Per Square Meter) 



in River Border and Side Channel Habitats Along the Lower 80 Miles of 



the Illinois River in 1915, 1964, 1974, and 1975^ 



Turbellaria (flatworms) 



Hirudinea (leeches) 



Oligochaeta (worms) 



Gastropoda (snails) 



Pelecypoda (clams) 



Sphaeriidae (fingernail clams) 

 Corbiculidae (Asiatic clams) 

 Unionidae (mussels) 



Insecta (insects) 



Odonata (dragonf lies) 

 Ephemeroptera (mayflies) 

 Coleoptera (beetles) 

 Trichoptera (caddisflies) 

 Diptera (midges) 



because no samples from the main channel were taken in 1975 and 1964. 



1921a: 490-493. Fifty-nine samples were taken in August. 

 Averages reported for three reaches of the river between mile 0.0 and 

 80.0 were weighted according to sample size and then averaged. 



Illinois Natural History Survey at Havana. Ten samples were taken 

 between river mile 19.3 and 30.8. 



1975: G15-G20. Nine samples were taken in September between 

 river mile 81.0 and 2.5. Samples taken in side channels were included because 

 side channels were sampled in the other surveys. One sample taken downstream 

 from a dike was not included because this type of habitat was not sampled in 

 the other surveys. 



e Anderson, 1977: 23. Twenty samples were taken in August between river 

 miles 58.0 and 18.9. 



22 



