TABLE 5-2 Distribution of predominant fish species in si 

 habitats of central Illinois (after Thompson and Hunt 1930). 



Common Name 



Gravel 



and sand Mud 



bottom bottom 



pools pools 



Suckermouth minnow + 



Banded darter + 



Bigeye chub + 



Log perch + 



Green-sided darter + 



Stonecat + 



Hog sucker + 



Fantail darter + 



Steelcolor minnow + 



Common shiner + 



Channel catfish + 



Hornyhead chub + 



StoneroUer minnow 

 Silverjaw minnow 

 River shiner 



Reffin shiner 

 Rainbow darter 

 Quillback carpsucker 

 Smallmouth bass 

 White crappie 



Orangespotted sunfish 

 Longear sunfish 

 Green sunfish 

 Bluntnose minnow 

 White sucker 



Northern redhorse 

 Shorthead redhorse 

 Creek chub 

 Johnny darter 

 Golden shiner 



Creek chubsucker 

 Grass pickerel 

 Blackstripe topminnow 

 Pirateperch 

 Freshwater drum 



Gizzard shad 

 Highfin carpsucker 

 Largemouth bass 

 Bigmouth buffalo 

 Carp 



Black crappie 



Black bullhead 



Total species 12 



ing on the rocks, on sand bottoms, and in small mud- 

 bottom streams rich in organic matter. The general 

 form of the body is similar to that of swift-water may- 

 fly naiads, although the gills are filamentous and lo- 

 cated at the base of the legs. 



Caddisfiy larvae occur most abundantly in streams 

 with medium to swift currents, but some species oc- 



cur only in sluggish rivers, in lakes, or in pond vege- 

 tation. Caddisfly larvae are of especial interest be- 

 cause of the cases they construct, in which the pupae 

 also occur later. In some species these cases are 

 portable. They are made of pieces of leaves, twigs, 

 sand grains, or stones which are cemented or tied 

 together with silk that the animals secrete. In stand- 

 ing or sluggish water, the cases are often large and 

 made of buoyant plant material, or they may be made 

 of sand grains, more fragile and slender. In swift 

 water, the cases are stout, cylindrical, tapered pos- 

 teriorly, and are usually smaller and more solidly 

 constructed of sand, small pebbles, or rock fragments 

 (Dodds and Hisaw 1925). The Hydropsychidae, 

 Philopotamidae, and Psychomyiidae are unique in 

 spinning fixed abodes in the form of a finger, a trum- 

 pet, or a tube. The Hydropsychidae erect a net at 

 the front end of the tube to catch particles of food 

 washed down with the current. Some psychomyiid 

 larvae, particularly Phylocentropus. burrow into sand 

 and cement the burrow walls into fairly rigid cases. 

 Some larvae belonging to the Rhyacophilidae are 

 free-living. Found in algal growth, they crawl 

 around seeking food, and are provided with large 

 abdominal hooks as clinging devices to supplement 

 the legs for clinging. However, they form a stone 

 case, or cocoon, for pupation (Ross 1944). 



The black fly larvae, Simuliidae, are often very 

 abundant in the swift waters of mountain brooks and 

 northern streams. The larvae secrete from their sali- 

 vary glands a delicate silken thread by which they 

 attach to the rocky substratum, and by manipulation 

 of which they can move short distances. At the pos- 

 terior end of the semi-erect body is a circlet of rows 

 of outwardly directed hooks which, when the muscles 

 of the disk are relaxed, move outwards and catch on 

 to a silk web placed there previously by the larva; 

 the anterior end of the body then swings freely in 

 the current. There is a fan-like food-gathering organ 

 on each side of the mouth. Before pupation, the lar- 

 vae spin a sedentary cocoon. The pointed end faces 

 the current and the other end, open, faces down- 

 stream. Out of it, the peculiar gills of the pupa float 

 in the water (Hora 1930, Nielsen 1950). 



The net-veined midge larvae, Blepharoceridae, 

 are unique in possessing six unpaired suckers on the 

 ventral side, by means of which they fasten to the 

 substratum. The original segmentation of the body 

 is almost obliterated ; it has been replaced by a sec- 

 ondary segmentation correspondent with the number 

 of suckers. 



Adult riffle beetles (Psephenidae, Dryopidae, 

 Elmidae) are small in size and are the only coleopter- 

 ans that live in or near rinming water. The legs are 

 not fitted for swimming, but rather possess hooked 

 claws for clutching the substratum. The body is cov- 

 ered with silken hairs that hold a thin film of air 

 about it when the beetle is submerged. The larvae 



46 Habitats, communities, succession 



