3Q G, C. Embody. 



XI. Some Enemies of Amphipods. 



The organisms which seem to cause the greatest destruction to 

 amphipods in the waters studied are found among the fishes, birds and 

 aquatic insects. 



During each spring thousands of young pike (Esox lucius) are 

 hatched and reared in the Ithaca marshes. Both adults and young 

 were collected during the years 1909 and 1910 and their stomachs 

 examined. There were very few between the ages of eighteen and 

 fourty-two days (length 24 to 47 mm) which had not eaten one or 

 more amphipods. One young pike 36,5 mm, long contained fourteen 

 (six E. gracilis and eight Hyalella) and in the stomach of a third, 

 44 mm long, were found ten specimens of E. gracilis. No amphipods 

 were found in pike over 52 mm, in length. 



One perch (Perca flavescens) 100 mm, long had eaten seven 

 amphipods (G. fasciatus). The stomachs of many young sun fish 

 (Eupomotis gibbosus) varying in length from 25 to 60 mm, were 

 found to contain from one to six amphipods. 



It is common knowledge that the eastern brook trout (Salvelinus 

 fontinalis) feeds upon amphipods and especially upon the so called 

 "Caledonia shrimp", (G. limnaeus). Three young trout approximately 

 100 mm, long and captured in January had eaten five and seven large 

 "Caledonia shrimps" respectively, notwithstanding the great abundance 

 of Hyalella and E. gracilis in the same stream. Mather (1900, p. 133) 

 states that he believes "Gammarus is greatly overrated as trout food". 

 The stomachs of 247 trout taken from Wilmurt Lake, Herkimer County, 

 New York, were examined by him and were estimated to contain but 

 five percent "Gammarus". The same ratio was found to obtain in 138 

 stomachs of trout taken from Meacham Lake in the Northern Adiron- 

 dacks of New York. He further states that a trout of a pound weight 

 seldom eats them. 



Among the fishes mentioned by Forbes (1908) as having fed upon 

 amphipods one finds, Notropis heterodou, Schildeodes gyrinus 

 (tadpole cat), Umbra limi (mudfish), Esox vermiculatus (pickerel), 

 Fundulus diaphanus menona, Fundulus notatus, Eupomotis 

 gibbosus, Perca flavescens and Microperca punctulata. 



A few instances among the birds have come to the writer's notice. 

 Messrs. A. A. Allen and J. T. Lloyd of Cornell University have found 

 many amphipods in the stomachs of Virginia rails (Rallus virginianus) 

 and a few in those of sora rails (Porzana Carolina). In each of 

 two red-wing blackbirds (Agelaius phoeniceus) taken October 15, 



