55 



inferior to them. That insect larvse should be more abundant 

 in the food of fresh-water fishes than are crustaceans, is a some- 

 what unexpected fact, but while the former make about twenty- 

 five per cent, of the food of our entire collection, the crustaceans 

 amount to only fourteen per cent. Crayfishes made about a 

 sixth of the food of the burbot, about a tenth that of the 

 common percli, a fourth that of half a dozen gars, and not far 

 from a third that of the black bass*, the dog-fish, and our four 

 rock bass. Young crayfishes appeared quite frequently in 

 some of the larger minnows (Semotilus and Hybopsis), and 

 also in catfishes, especially the pond and river bull-heads, aver- 

 aging nearly fifteen per cent, of the entire food of the two most 

 abundant species. 



The minute crustaceans commonly grouped as Entomostraca 

 are a much more important element. Among full-grown fishes, 

 I find them especially important in the shovel-fish — where they 

 made two thirds of the food of the specimens studied — and in 

 the common lake herring. Among the sunfishes at large they 

 were present in only insignificant ratio ; but the croppies, dis- 

 tinguished by long and numerous rakers on the anterior gill, 

 had derived about a tenth of their food from these minute 

 crustaceans. In the early spring, especially, when the back- 

 waters of the streams arc filled with Entomostraca, the stomachs 

 of these fishes are often distended with the commonest forms. 

 Ten per cent, of the food of the sucker family consisted of them, 

 mostly taken by the deep-bodied species, in which they made 

 a fourth or a fifth of the entire food. This fact is explained, it 

 will be remembered, by the relatively long, slender, and numer- 

 ous gill-rakers of these fishes. Large river buffalo were 

 occasionally crammed with the smallest of these Entomostraca, 

 only a twenty-fifth of an inch in length. 



I have several times remarked the peculiar importance of 

 Entomostraca to the shovel-fish — one of the largest of our fresh- 

 water animals — a fact accounted for by the remarkable branchial 

 strainer of this species, probably the most efficient apparatus of 

 its kind known to the ichthyologist. Here, again, the smallest 

 forms were the most abundant. 



Oar specimens — especially of the small-inouthed black bass — werel 

 veratre reliable. 



