246 FISHES OF ILLINOIS 



grayish to olive, with darker mottlings, the spots forming irregular rows. 

 Head rather large, 2.4 to 2.6; width of head 1.9 to 2 . 1 in its length 

 interorbital space 3 . 9 to 4 . 3 ; eye 4 to 5 ; nose longer than eye, 3.3 to 4 . 4 

 mouth very large, maxillary nearly to back of orbit, 2 .2 to 2 .4 in head 

 operculum prolonged backward and rounded behind as in Lepomis and 

 Eupomotis, the membranous flap narrow; gill-rakers 8 or 9 + rudiments, 

 rather long and stiff. Dorsal X (occasionally IX or XI), 9 or 10 (or 11) ; 

 long and low, longest spine 3 . 5 to 4 in head ; base of dorsal twice length 

 base of anal; caudal lunate; anal III, 8-10; ventrals short of vent in 

 females, to vent in males; pectorals short of front of anal, 1 . 5 to 1 . 8 in 

 head. Scales 6 or 7, 39-43, 11 or 12 (occasionally 13); lateral line usu- 

 ally complete; 6 to 8 rows of scales on cheeks. 



The warmouth is a heavy, wide-mouthed, red-eyed sunfish, dark 

 and mottled like the rock bass, but with less of bronze or other 

 showy color. This fish, the rock bass, and the green sunfish form a 

 group of abundant Illinois species, all with large mouths, and all 

 feeding almost wholly on fishes and insects. Notwithstanding this 

 similarity of food, they seem to have learned to inhabit the same area 

 without serious mutual competition by establishing different rela- 

 tions to their environment. The rock bass, as already shown, lives 

 by preference in clear waters flowing over a rock bottom, while the 

 present species is the most of a mud lover of all of our sunfishes, as 

 shown by its preference for a muddy bottom, represented in our col- 

 lections by the surprising coefficient of 7 .33. Other factors of this 

 adjustment will be considered in the discussion of the green sunfish. 



The warmouth is essentially a species of lakes and ponds and the 

 smaller rivers, occurring also, but less generally, in creeks and in 

 rivers of the largest class. It is distributed throughout the state — 

 in the southern section mainly in the smaller streams, but in the 

 northern half chiefly along the Illinois River It is abundant in the 

 glacial lakes of northeastern Illinois, and has come to us also from 

 Lake Michigan. In the southern part of the state it is common in 

 the lower Illinoisan glaciation, to an extent to indicate a deliberate 

 preference for muddy water over pure. It is seemingly a southern 

 species by preference in this state, the frequency ratios for the three 

 sections being .44, .78, and 1 . 78, from north to south. 



Lakes Michigan and Erie seem to mark its most northerly dis- 

 tribution, and from these it is found to the Florida peninsula on the 

 southeast, and to Louisiana, Texas, and Kansas on the south and 

 west. It is said to be common in South Carolina, but is most abun- 

 dant west of the Alleghanies. It is everywhere a fish of the bayous, 

 mud-bottomed ponds and lakes, and lowland streams. 



