107 
ecome larger and more abundant in the food. The adults eat 
oraciously of a great variety of fishes--especially, the hickory shad 
Dorysoma),—and feed upon crawfishes also to some extent. 
Microprervs saLMorpes, Lac. Smauu-MoutHep Brack Bass. 
This species, called also tiger bass, river bass, eté., is the black 
ass, par excellence. It ranges, usually, in deeper and clearer water 
han the preceding; but both are often taken together. 
I have made full notes of the food of twenty-seven specimens,— 
hree adult and the others young. I had none of this species under 
n inch in length; but, judging from the general resemblance of the 
ood of this and the preceding bass at later ages, I do not doubt 
hat this will also be found to feed at first on Hntomostraca, 
Ithough insect food is possibly more important to 1t from the be- 
qnning. 1 
Seven individuals, from one to two inches in length, were all 
aken in July from rocky ripples in the Fox River, at Dayton, ‘Ill., 
t few miles above the mouth of the stream. These had eaten only 
ive per cent. of Entomostraca,—the whole remainder of the food 
sonsisting of insects, of which Coriza tumida, young and adult, and 
arve of May-flies and darning-needles (Agrionidx) were the most 
mportant kinds. Four per cent. of the larve of Chironomus are 
yorthy of notice. The scarcity of Entomostraca in the food of fishes 
ys small as these is probably due to the situation in which these 
specimens occurred, as few Entomostraca are to be found in swift 
water. The same fact will account for the presence of Chironomus 
arve,—found abundantly under stones in rapid streams. 
The next ten specimens, between two and three inches long, were 
saken in July, partly at the same place as the preceding, and partly 
‘rom the Illinois River, a few miles below the mouth of the Fox. 
These differed from the smaller specimens chiefly in the appearance 
of fishes in the food (five per cent.) and in the absence of Neurop- 
tera. Probably the last of these differences, at least, was accidental. 
A few larve of aquatic Coleoptera (Hydrophilide and Dytiscide) 
were noticed. Corixas, including C. twmida, Uhl., and C. signata, 
Fieb.,* amounted to eighty-two per cent. of the food. 
In those ranging from three to four inches in length (seven in- 
dividuals), the fishes eaten rise to fourteen per cent., but the insects 
drop away to seven per cent., and the Crustacea rise to seventy- 
nine. Here, however, difference of locality interferes to prevent any 
satisfactory comparison with other ages,—as these specimens were 
all taken in August, from Calumet River, at South Chicago. This 
slow stream, clogged with, Alge and a great variety of other aquatic 
plants in midsummer, also swarms with Crustacea,—especially the 
little Allorchestes dentata. .. This species made sixty-three per cent. 
of the food of these specimens; and an undetermined species of 
Asellus, fourteen per cent. A few Gammarus fasciatus were also 
found. The insects were Corixa and larve of Agrionide. 
*Determined by Mr. Uhler. 
