62 FISHES OF ILLINOIS 



The family is found in the fresh waters of North America at 

 large, in which about 15 genera and 60 species occur; and there 

 are 2 species also in eastern Asia. They range in length from 6 

 inches to 3 feet. The suckers have usually been regarded by Euro- 

 pean writers as a subfamily of CyprinidcB, from which they differ 

 chiefly in the structure of the mouth and the lower pharyngeal 

 bones. They are generally of sluggish habit and, as a rule, prefer 

 water of good depth and little current, but some of them may be 

 found in almost every stream and pond within their range. Their 

 spring migration is familiar to all fishermen, and to many who do 

 not fish, all of our species running up the smaller streams in May or 

 June to deposit their eggs. The males of most species develop 

 black or red pigment on the body and fins in spring, and in many 

 kinds peculiar wart-like tubercles, called pearl organs, appear at 

 this season on the head, fins, and caudal peduncle. 



The suckers are, on the whole, an unusually homogeneous group 

 as represented in Illinois, not only agreeing in the character of their 

 feeding structures which gives them their common name, but un- 

 usually similar also in their movements, habits, modes of life, and 

 places of most frequent resort. They feed, without exception, on 

 the bottom of the waters they inhabit, and commonly on substan- 

 tially the same kinds of food, difi^ering somewhat in respect to the 

 places in which they seek it. The buffalo-fishes, for example, are 

 from 2^ to 3 times as abundant in our collections from the bot- 

 tom-land lakes as they would be if they had been equally dis- 

 tributed throughout all waters. In other words, the frequency 

 coefiicient of one of the two buft'aloes is 2.26 for lowland lakes and 

 that of the other is 2.93. On the other hand, the common sucker, 

 the chub-sucker, and the striped sucker show a decided preference 

 for the smaller streams, their coefficients of frequency in creeks 

 being 4.27, 3.41, and 3.17 for the three species respectively. The 

 most marked departure from the average habit of the family is 

 made by the hogsucker, or stone-roller (Catostomus nigricans), 

 which especially frequents swift water on rocky stretches of the 

 larger streams, filling there the place which the darters occupy in 

 creeks and brooks. 



Notwithstanding these divergencies in local distribution, the 

 family as a whole forms a rather definite ecological group, as is 

 shown especially by the frequency with which representatives of the 

 several species are found in company in the same situations and 

 appear together, consequently, in our collections. The average 

 frequency of this joint occurrence of the species of suckers and 



