228 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
mouth a small pond or lagoon which was searched with some care during half a day. 
This pond is shallow and muddy, but mostly clear in the middle, with a fringe of 
aquatic vegetation and stout marsh grass growing in the water. The clear water was 
full of lhinute spherical masses of algae, among which were a Diaptomus and Poly- 
phemus — apparently the usual lake species, but not preserved. In the grass were great 
numbers of Gammarus robustus and a few Allorchestes inermis , and ephemerid larvae 
were abundant everywhere. Ghironomus larvae were common in the collection and 
doubtless very abundant in the mud, and a robust Corethra larva was occasionally 
taken. Small water-beetles ( Deronectes and Haliplus ), caseworms with cases made of 
fragments of vegetation and others of line gravel, Gorisa, a water-skater ( Hygrotrechus ), 
black Poduridce , and occasional terrestrial insects were among the other insect elements 
available for the food of fishes. The mollusks of this little collection were small 
Limncece , Physce (large and small), Pisidium , and Valvata. Various leeches (the most 
abundant the common Nephelis maculata ), Hydrachnidm , and planarians complete the 
list thus far made up. 
The pond was swarming with young mountain trout ( Salmo myJciss ), a few of 
which I dissected for a determination of their food. One of these an inch and a half 
in length had eaten Ghironomus larvae and iinagos chiefly, the remainder of its latest 
meal consisting of other insect larvae not in condition to identify, and the entomostra- 
can Polyphemus pediculus. A second, an inch and a quarter long, had also fed mostly 
on Ghironomus in its various stages of larva, pupa, and imago, but had made about 
a third of its meal from entomostraca ( Daphnia pulex and Polyphemus pediculus). 
Another, still smaller (0.92 of an inch long), taken from the open lake, among the small 
weeds growing on a fiat, muddy rock, had filled itself with Ghironomus pup® only, as 
had still another of the same size. A third specimen from this situation had eaten 
more larv® of Simulium than of Ghironomus , and a fourth had also eaten Simulium 
larv® and another dipterous larva unknown to me. 
I may add here that other young trout, in a small, swift rivulet near the Lake 
Hotel, were feeding continuously, August 9, on floating winged insects, mostly, if not 
all, Ghironomus and smaller gnat like forms. 
The large leeches at Bridge Bay ( Nephelis maculata ) betrayed their scavenger 
habits by collecting in numbers upon a dead fish, which they were evidently feeding 
from. Two specimens taken elsewhere in this pond proved on dissection to have the 
alimentary canal nearly empty, one containing only a few fragments of Gammarus in 
the rectum, and the other a single leg of a Gammarus in the oesophagus. 
As illustrations of the smaller animal life of the river below the lake and in its 
vicinity, I may report the product of two trips made August 11 aud 23, one from a 
quarter to half a mile below the outlet, and the other to a point about a mile below. 
The most fruitful ground at the first locality was a sedgy flat on the left bank 
and a bed of flat rock covered with alg;e and other fine vegetation, with about 6 to 8 
inches of water. Other collections were made from the bare sandy bottom, in water 6 
inches deep, witli moderate current. 
On the weedy rocks occurred the large hairy Gypris described herewith (p. 214) as 
G. barbatus , and other small blue cyprids not yet studied. The presence of Ghirono- 
mus larv®, several sorts of caseworms, larv® of ephemerids, Hygrotrechus , Gorisa (larva 
and adult), various water-beetles, specimens of Gammarus robustus and Daphnia pulex, 
