228 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



mouth ;i 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 minute spherical masses of alg;e, among which were a Diaptomus and Poly- 

 phemus apparently the usual lake species, but not preserved. In the grass were great 

 numbers of Oammnrus robustus and a few Allorchestes iiiermis, and ephemerid larvae 

 were abundant everywhere. Chironomus larvae were common in the collection and 

 doubtless very abundant in the mud, and a robust Gorethra larva was occasionally 

 taken. Small water-beetles (Deroneutes and Hciliplun), caseworms with cases made of 

 fragments of vegetation and others of line gravel, Corisa, a water-skater (Hyyrotrechus), 

 black Podutidcv, and occasional terrestrial insects were among the other insect elements 

 available for the food of fishes. The mollusks of this little collection were small 

 LlmncBce, Physfc (large and small), Pisidium, and Valvata. Various leeches (the most 

 abundant the common Nephelis maculata), Hydrachnidce, and plauarians complete the 

 list thus far made up. 



The pond was swarming with young mountain trout (Salmo mykiss), a few of 

 which I dissected for a determination of their food. One of these an inch and a half 

 in length had eaten Ghironomun larvse and imagos chicHy, the remainder of its latest 

 meal consisting of other insect larvie not. in condition to identify, and the entomostra- 

 can Polyphemus pcdiculus. A second, an inch and a quarter long, had also fed mostly 

 on Ghironomux in its various stages of larva, pupa, and imago, but had made about 

 a third of its meal from entomostraca (Daphnia pulex and Polyphemus ped,iculus). 

 Another, still smaller (0.92 of an inch long), taken from the open lake, among the small 

 weeds growing on a flat, muddy rock, had filled itself with Chironomus pup;o only, as 

 had still another of the same size. A third specimen from this situation had eaten 

 more larva* of Simulium than of Chironomus, and a fourth had also eaten Simulium 

 Iarva3 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 !>, on floating winged insects, mostly, if not 

 all, Chironomus and smaller gnat-like forms. 



The large leeches at Bridge Bay (Nephelis maculuta) 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 Gamm/irus 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 and 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 algaj 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, with moderate current. 



On the weedy rocks occurred the large hairy Gi/pris described herewith (p. 244) as 

 G. barbatus, and other small blue cyprids not yet studied. The presence of Ghirono- 

 mus larvae, several sorts of caseworms, larva) of ephemerids, Hygrotrechus, Gorisa (larva 

 and adultl, various water-beetles, specimens of Gammarus robustus and Daphnia pulcx, 



