534 Bulletin American Museum of Natural History [Vol]. LIII 
present on this subject. J.G. Mt cidhatl found that the food of the North 
American bullfrog, Rana catesbiana Shaw, consists mainly of insects and 
snails [at Saranac Inn, N. Y.., all of one species: Physa heterostropha (Say) | 
and that the bulk of the snails eaten was greater than that of the insects 
of any single order. According to C. J. Drake,? gastropods (mainly 
aquatics: Goniobasis. Lymnxa, and Physa; also Zonitoides arbcreus) 
constitute 3 per cent of the animal food of the leopard frog, Rana pipiens 
Schreber, in Ohio, and were seen in 10 per cent of the 209 stomachs 
examined. Mollusks were found in small numbers in the stomach of all 
five species of Rana of the Belgian Congo examined by Mr. G. K. Noble 
(see table, p. 473) andit is most likely that in this case they were aquatic 
snails, although they were not identified. 
Mollusks form a substantial part of the food of fish, as is well brought - 
out by J. W. Taylor’: 
“The beneficial effect of water-snails as nourishing food, especially for trout, is 
shown by the rapid growth of fish placed in streams or ponds in which mollusks 
abound. The ravages of fish amongst mollusks are not, however, confined to such 
species as disport themselves more or less actively at the surface or amongst the 
vegetation, but is also carried on amongst the minute mud-loving Pisidia, which 
in America have been shown to be an important food of the Whitefish [Coregonus 
cluperformis (Mitchill)]. The Gillaroo trout, which lives in the Irish loughs, and other 
famous breeds also, subsist chiefly upon mollusks which give them the exquisite 
flavour which has rendered them so famous and prized by epicures. Specimens of the 
‘Gillaroo trout have been caught gorged to repletion with Bithynia tentaculata and 
other fresh-water species, and the remarkable and peculiar thickening of the stomach- 
wall of this trout has been attributed to the fact of shelled snails forming so large a 
part of its diet. The eel is another rapacious devourer ef the Mollusca, as many 
as 350 shells of Valvata piscinalis, in addition to those of other species, having been 
obtained from the stomach of a single eel. The barbel has been noted as having a 
special predilection for Valvata piscinalis and also for Spherium corneum, and many 
fish, and more especially gold carp, regard Physa fontinalis as a choice and delicate 
morsel, while the roach is tecorded to feed even upon the eggs of the various species.”? 
The examination of the contents of the stomach of fishes obtained — 
from natives may furnish the collector with valuable specimens. In this 
fashion the junior author secured some of the peculiar melanians that 
inhabit Lake Moero. 
Aquatic birds are probably the most destructive enemies of fluviatile 
snails and mussels and some species appear to be almost restricted to that 
diet.* Shore birds, such as wagtails (Motacilla), dipper (Cinclus aquaticus 
11905, N. Y. State Mus. Bull. 86, p. 12. 
21914, Ohio Naturalist, peri p. 263. 
31894-1900, op. cit., p. 419. 
‘Attention was called above (p. 531) to the curious habit certain birds have of concealing live 
snails in their plumage. 
