234 FISHES OF ILLINOIS 



position of the several species to avoid each others' company, 

 some of the species having been found together in our collections 

 with more than twice the average frequency, and others with less 

 than a third that average. The family affords, indeed, an 

 excellent illustration of the disposition of species closely allied 

 in structure and in classification and inhabiting the same area to 

 evade the mutually injurious competition to which their similar 

 natural endowments expose them, by avoiding each others' 

 company — ^by choosing, as a rule, different feeding grounds and 

 different places of resort. If we compare, for example, the pro- 

 portionate frequency with which the closely similar species of 

 the genus Lepomis have been taken together in our collections^ 

 in the same haul of the net, or from the same situation at the 

 same time — with the frequency of associate occurrence of the 

 widely dissimilar species of the other genera of the family, we 

 find that the unlike species have been taken together much more 

 frequently than the like — in a ratio of 13^ to 1 ; that the species of 

 Lepomis have, indeed, been taken in company with species of 

 other genera considerably more frequently than with each other. 

 The sunfishes, consequently, are not an associate group, but 

 tend to disperse themselves over a large varietj^ of ecological 

 situations, those least like each other being most likely to meet 

 on common ground, where their unlike capacities enable them 

 to live together in a non-competitive way. 



Of our fifteen species of sunfishes proper, including the 

 crappies in this number, eleven are abundant enough in this 

 state to play a significant part in the Hfe of the family. Three of 

 these species have a more or less limited general distribution 

 within the state. The round sunfish {Centrarchus macroptenis) 

 is confined to extreme southern Ilhnois; the pumpkinseed 

 {Eupomotis gibbosus) is found almost wholly in the northern half 

 of the state, and, except in northern Illinois proper, only along 

 the main streams of the largest rivers; and the long-eared sunfish 

 {Lepomis megalotis), which is distributed throughout the state, 

 is so concentrated in southern and eastern Ilhnois that its com- 

 petitive relations are strongly affected by this fact. The war- 

 mouth (Chaenobryttus gulosus) is, indeed, somewhat similarly 

 distributed, the contrast being, however, less marked than in 

 megalotis. The rock bass {Ambloplites rupestris) is sharply 

 separated from most of the other sunfishes by its strong prefer- 

 ence for swift, clear streams; the bluegill {Lepomis pallidus), the 

 warmouth, and Lepomis miniatus are rather strongly distin- 



