Distribution, Food and reproductive Capacity of some fresh-water Amphipods. 31 



1909, in the Ithaca Marsh, Mr. Allen found a single amphipod. 

 A swamp sparrow (Melospiza georgiana) and a long-billed marsh 

 wren (Telmatodytes palustris), taken in June and July 1909, re- 

 spectively, each had devoured two Hyalellas. In the stomachs of a 

 spotted sandpiper (Actitis macularia) collected July 15, 1909, fivo 

 amphipods were found. 



The most remarkable instance which has come to hand is that of 

 a king eider duck (Somateria spectabiUs) captured by Mr. J. T. Lloyd 

 November 26, 1909, in the Montezuma Marshes near the north end of 

 Cayuga Lake. Among other animals, 72 specimens of G. fasciatus 

 were found in its enteron (Embody 1910). 



Among the msects, the larva of dytiscid beetles, damsel flies 

 (Lestes) and dragon fUes (Anax) have been observed to capture and 

 partially devour amphipods. Many back- swimmers (Notonecta) were 

 seen to pursue, captm-e and kill amphipods as large as themselves. 



It was thought that Hydras which Uved in abundance in vege- 

 tation which furnished retreats for amphipods, might capture and devour 

 the young of the latter. Accordingly several Hydras and young amphi- 

 pods of different ages were placed together in watchglasses. It was 

 demonstrated that young amphipods up to the age of eight days for 

 G. limnaeus and G. fasciatus, and thirteen days for Hyalella, were 

 readily captured and devoured. Young Hyalellas, fifteen days old, 

 readily escaped from the tentacles and seemed not to be affected by 

 the nettle cells. The young of E. gracilis were easily captured and 

 killed as late as the fortieth day. 



Bladders of Utricularia which destroy immense numbers of 

 Entomostraca were opened but none was found to contain remains 

 of amphipods. The living plants were placed in aquaria containing 

 amphipods but as far as the writer could determine none of the latter 

 was captured. A young Hyalella was made to enter one of the living 

 bladders. The following day this particular bladder possessed an irre- 

 gular hole half way to the opening but no amphipod remains. Since 

 Hyalellas were often seen eating the bladders from the outside, it is 

 believed that the hole was made either by the imprisoned Hyalella 

 or by one without. At any rate the original amphipod escaped. 



Summary. 



1. In the waters investigated, Gammarus limnaeus and Gammarus 

 fasciatus grow to the greatest size, Eucrangonyx gracilis third and 

 Hyalella knickerbockeri, fourth. 



