234 FISHES OF ILLINOIS 



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 

 - -1 >y choosing, as a rule, different feeding grounds and different places 

 of resort. If we compare, for example, the proportionate 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 

 ( incurrence 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 Hto 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 variety 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 life of the family. Three of these species have 

 a more or less limited general distribution within the state. The 

 round sunfish (Centrarchus macropterus) is confined to extreme south- 

 ern Illinois; the pumpkinseed (Eupomotis gibbosus) is found almost 

 wholly in the northern half of the state, and, except in northern Illi- 

 nois 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 Illi- 

 nois that its competitive relations are strongly affected by this fact. 

 The warmouth (( 'hcenobryttus gulosus) is, indeed, somewhat similarly 

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

 lotis. The rock bass (Ambloplites rupestris) is sharply separated 

 from most of the other sunfishes by its strong preference for swift, 

 clear streams; the bluegill (Lepomis ptillitlits), the warmouth, and 

 Lepomis miniums are rather strongly distinguished by their greater 

 frequency in lakes and ponds; while the warmouth and Lepomis 

 humilis are especially noticeable because of their high frequencies 

 over a muddy bottom. The principal species of the larger rivers are 



