214 NORTHERN FISHES 



under a stone or a leaf, his tail bent around the stone as if for support 

 against the force of the current. You will remember that when your 

 finger came near the spot where he was lying, the bent tail was straight- 

 ened, and you saw the fish again resting, head upstream, a few feet away, 

 leaving you puzzled to know whether you had seen the movement or 

 not. You were trying to catch a Johnny Darter. Nothing seems easier, 

 but you did not do it." 



The largest darters reach a length of 8 inches, but the average is about 

 2 1/2 inches. Most of the species usually prefer clear running water, 

 where they rest on the bottom among the stones. When frightened or 

 hungry they dart swiftly for a short distance, coming to rest suddenly 

 on their large pectoral fins. As they rarely leave the bottom when rest- 

 ing they are never seen suspended in the water. A few species seek a 

 sand bottom, where they lie buried with only the eyes visible. Darters 

 feed chiefly on Entomostraca and the larvae of insects. 



Upon the origin of the group as a whole Forbes (1884, quoted from 

 Jordan, 1904) wrote: "Given a supply of certain kinds of food nearly 

 inaccessible to the ordinary fish, it is to be expected that some fishes 

 will become especially fitted for its utilization. Thus Etheostoma is to be 

 explained by the hypothesis of the progressive adaptation of the young 

 of certain Percinac to a peculiar place of refuge and a peculiarly situ- 

 ated food supply. These are the mountaineers among fishes. Forced from 

 the populous and fertile valleys of the river beds and lake bottoms, they 

 have taken refuge from their enemies in the rocky highlands, where the 

 free waters play in ceaseless torrents, and there they have wrested from 

 stubborn nature a meagre living. Although diminished in size by their 

 constant struggle with the elements, they have developed an activity 

 and hardihood, a vigor of life and a glow of high color, almost unknown 

 among the easier livers of the lower lands. Notwithstanding their trivial 

 size, they do not seem to be dwarfed so much as concentrated fishes." 



GENUS Imostonm Jordan 



RIVER DARTER 



Imostoma shumardi (Girard) 



The body of the river darter (Figure 40A) is robust, the head broad 

 and thick, and the mouth large. The scales number 6-56-11. The cheeks, 

 opercles, and nape are scaly; the breast is naked. The dorsal spines num- 

 ber 10 and the soft dorsal rays 15. The anal spines number 2 and the 

 soft rays 11. The color and markings are dark olive blotched with even 

 darker olive; the sides have 8 to 10 vague bars. The river darter may 

 be readily identified by the black spots between the first and second 

 spines and between the last three spines in the first dorsal fin. The fins 



