CYPRINID.« THE MINNOWS AND THE CARP 97 



take our miscellaneous collections to have been fairly distributed as 

 to varieties of situation and to proportionate extent of each 

 variety, we may further infer from our data that minnows will 

 generally be found over a relatively hard and clean bottom about 

 two and a half times as abundanth^ as over a bottom of mud. 



In the general scheme of aquatic life, the native members of this 

 family, taken together as a group, play a multiple role. They 

 operate, to some extent, as a check on the increase of the aquatic 

 insects, from which they draw a large part of their food supply ; they 

 make indirectly available, as food for their own most destructive 

 enemies, these aquatic insects, many terrestrial insects also, which 

 fall into the w^ater and are greedily devoured by them, and the mere 

 mud and slime and confervoid algae gathered up from the bottom of 

 the waters they inhabit ; and they rival the young of all larger fishes, 

 their own worst enemies included, by living continuously, to a 

 great degree, on the Entomostraca and insect life which these fishes 

 must have, at one period of their lives, in order to get their growth. 

 They also offer a considerable means of subsistence to certain 

 aquatic birds, such as kingfishers, and members of the heron family; 

 and, through their contributions to the support of the best food 

 fishes, they form an important link in the chain of agencies by 

 which our waters are made productive in the interest of man. 



Among the enemies of CyprinidcB disclosed by our study of 1,221 

 Illinois fishes, already referred to, are practically all our most pre- 

 daceous fishes, including the dogfish, both our common species of 

 gar, the wall-eyed pike, both our species of pickerel, both species of 

 black bass, the yellow perch, the mud-cat, the bullheads, the crap- 

 pies, the green sunfish, and, finally, one of their own family, the 

 horned dace. That this list might be considerably enlarged by 

 more extensive studies of the food of fishes is beyond a doubt, and 

 it is safe to say that no fish-eating fish would, if hungry for fish, re- 

 fuse a minnow of any kind unless it seemed too small to be worth the 

 trouble of capturing. 



From the standpoint of the predaceous species, minnows are 

 young fishes which never grow up, and thus keep up the supply 

 of edible fishes of a size to make them available to the smaller 

 carnivorous kinds when the young of the larger species have grown 

 too large to be captured or eaten. ' They thus not only furnish the 

 necessary food to the smaller aquatic Carnivora, but they ease the 

 way of growth to the largest kinds, all of which pass through a 

 period when they need fish food, but are not yet large enough to 

 capture the prey upon which they chiefly depend when they are 



