106 
americanus, Birge, was also an important element; and traces ap-_ 
pear of Chydorus, Pleuroxus and Eurycercus lamellatus. About sim 
per cént. of Cyclops had been eaten. 
In the food of the next group—six specimens, from 1; to P| 
inches long—minute fishes and insects appear. ‘The fishes (twenty- 
nine per cent.) were not large enough to determine. The insects” 
(forty-six per cent.) were mostly young water bugs (Corixa), the 
principal part of which weye about half grown. ‘The adults were 
all Coriva tumida, Uhl. The Entomostraca- drop to twenty-five per 
cent., about equally Cladocera and Cyclops. Among the former? 
were “many specimens of Simocephalus americanus, and a few of the 
rare and curious Leptodora mentioned in a previous paper.* The, 
specimen in which this was found was taken at Peoria, in June, 
1878. All of this group were taken from the Illinois River, but at 
different places and dates. Some, taken at the same place and 
time as others of the preceding group, differed from them in the 
smaller number of Entomostraca eaten, and the larger number of 
insects,—differences evidently only to ‘be explained as due to the 
different sizes of the fishes. 
The next two specimens, between two and three inches long, had 
eaten only insects, chiefly Corixa tumida. 
Four specimens, ranging from three to three and a half inches 
in length, all taken from a lake in the Illinois River bottom, in Oc- 
tober, 1879, had eaten nothing but insects,—almost wholly Corixas” 
and the larve of May-flies (Ephemeride). The Corixas were C. 
alternata, Say, and C. tumida, Uhl. a 
Food of the Adult. 
Turning to the food of the fourteen adults, we note the total dis- 
appearance of HEntomostraca, the merely accidental occurrence of 
insects, the appearance of crawfishes (Cambarus ummunis), which — 
amount to seven per cent. of the whole food, and the great pre- 
dominance of fishes (eighty-six per cent.). These were of sufficient 
variety to show that no group is safe from the appetite of the bass, é 
unless it be the gar. 
Perch, minnows, catfish and hickory shad were recognizable. the 
last were much the most abundant, occurring in eight of the speci- 
mens, and constituting fifty-eight per cent. of the food of the whole 
number. They ranged from three to six in each stomach, and were 
from three to four inches long. It should be noted, however, that 
these were all eaten by fishes taken at the same place and time. 
A large mouse was found in the stomach of one bass from the Uli= 
nois River. | 
We may generalize these data by saying that this. black baad 
lives, at first, wholly on Entomostraca; that it commences to take | 
the smallest aquatic insects when about ah inch in length, and that 
minute fishes appear in its diet almost as early. From this forward, 
the Entomostraca diminish in importance, and the insects and fishes. 
— 
* See Bull. No. 2. Ill. State Lab. Nat. Hist., p. 88. 
/ 
