20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



The ostracods have been identified chiefly from the stomachs of 

 15 species of wild ducks, and no fewer than 1,200 have in two in- 

 stances been taken from a single stomach. Most of the barnacles 

 were found in the stomachs of 22 species of ducks, gulls, and shore- 

 birds from northern waters. Amphipods were eaten by more than 80 

 species of birds, largely shorebirds, ducks, and other waterfowl ; nearly 

 70 species of amphipods were identified and the number of individuals 

 taken by single birds ran up as high as 2,500. The isopods were con- 

 sumed by more than 75 species of birds, the land-forms or pillbugs 

 alone by about half that many; the greatest number of individuals 

 of terrestrial sowbugs found in a single stomach was 60, of aquatic 

 forms, 256. In the Decapoda it may be of interest to note that 392 

 of the identifications were of shrimps, hundreds of individuals being 

 present in some stomachs ; 1,592 of Astacidae (crawfishes), the great- 

 est number taken by one bird being 49 ; and 794 of crabs of various 

 kinds. Among groups of crabs represented, there were the following 

 numbers of captures, the figures in parentheses in each case denoting 

 the largest number of individual crabs found in a single stomach: 

 Sand crabs or sandbugs, Hippidae, 61 (14) ; stone crabs, Lithodidae, 

 90 (16) ; hermit crabs, Paguridae, 35 (40) ; mud crabs, Pilumnidae, 

 186 (36) ; swimming crabs, Portunidae, 39 (16) ; edible crabs, Can- 

 cridae, 41 (18) ; shore crabs, Grapsidae, 180 (26) ; and fiddler crabs. 

 Ocypodidae, 272 (19). 



Number of identifications 6,086 ; percentage of identifications 

 among those of all arthopods 2.8877 I percentage of species in this 

 group among the whole number of arthropod species known, 3.8254. 



Other enemies.- — Crabs of various genera (including hermits) are 

 a staple item of food for many fishes, such as the dogfish, rays, eels, 

 sea bass, squeteague, scup, tautog, swellfish, toadfish, tilefish, hake, cod, 

 haddock, sculpins, and flounders. Crawfishes are relished by fresh- 

 water fishes and are eaten also by snakes, turtles, and various mam- 

 mals such as the muskrat, raccoon, skunks, mink, and otter. Such large 

 and powerful forms as lobsters are eaten by sea bass, rockfish, tautog, 

 sharks, dogfish, rays, and skates. Amphipods are captured by the 

 plant Utriciilaria, by insects, hydras, sea-anemones, and starfishes. 

 Practically all adult fresh-water fishes eat amphipods and isopods, 

 and when young prey upon Cladocera, Copepoda and Ostracoda. 

 Starfishes and bony fishes such as Coregonus, Salvelinus, Alosa, her- 

 ring, sticklebacks, and roaches continue feeding on these small forms 

 when adult. Marine fishes take similar Crustacea available to them, 

 particularly the abundant shrimps and Mysidacea. Whales and seals 

 consume enormous quantities of isopods and Euphasiacea. Caprellids 



