53] STUDY OF SOUTHERN WISCONSIN FISHES— CAEN 53 



particularly in the Fox and Oconomowoc. It is an inhabitant of water of 

 moderate current and reasonable clearness, avoiding foul or muddy water. 

 The fish prefer a rocky or heavy gravel bottom to sandy bottom, and 

 avoid entirely mud or silt. Very fast in action, they are easily approached 

 but disappear under rocks or stumps as if by magic if disturbed. In this 

 characteristic only do they resemble the other darters. They feed on bottom 

 animal matter almost exclusively, Chironomus, Simulium, Allorchestes 

 and other small Crustacea, with occasionally a minute mollusk. They 

 have no particular economic value and are never used as bait because of 

 their small and tender mouth. I have found them as food in Micropterus 

 salmoides, Esox lucius and Stizostedion vitreum. 



78. Hadropterus as pro (Cope & Jordan). Black-sided Darter. 



A darter of the river systems only, taken in all but the Menomonee 

 river, particularly common in the Mukwonago and Fox rivers. A fish of 

 medium current, but preferring water a bit faster than the preceding. 

 Usually found where some vegetation is present into which the fish retreat. 

 Fine gravel is the preferred type of bottom but they are occasionally found 

 over muck, in which case the fish are decidedly darker in coloration. In 

 the Fox river they are associated with Esox americanus, Umbra limi and 

 Cottus sp.; in the Mukwonago especially with Semotilus atromaculatus. 

 The food is largely entomostraca and Crustacea (copepods) with large 

 numbers of insect larvae and nymphs. Spawning occurs early in June, 

 in shallow water, often under overhanging banks or amid vegetation, in 

 water of some current. 



79. Diplesion blennioides (Raf.). Green-sided Darter. 



Distinctly a stream species, though I have taken the species a number 

 of times in both Oconomowoc and La Belle lakes. Common wherever 

 found, this beautiful little darter prefers a sandy bottom and medium 

 current, being absent from rock and mud environments. On this sand they 

 lie supported by their very ample pectoral fins, as if they were resting on 

 their elbows, ready for instant departure. When they start off, the quick 

 flip of the tail stirs up the soft bottom in a whirl of sand and by the time 

 this settles, the darter is nowhere to be seen, having made good its escape 

 behind the "smoke screen." While I have never seen the nest in a 

 river habitat, I have found several in Oconomowoc lake. These have 

 invariably been under small pieces of water-logged wood, from beneath 

 which protrudes the peculiarly shaped head of the watching fish. This is 

 the male; and if an intruder of considerable size appears, he retreats under 

 his shelter without delay. If the enemy be a small minnow, the male 

 makes a furious dart out of his hole, flies at the intruder, and returns 

 again so quickly that about all one sees is a cloud of sand which conceals 

 for a moment the opening to the nest into which the male has dived. By 



