38 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



rather smooth contour or from a central point where it is 

 puckered or folded. 



ENEMIES. 



The principal enemies of the Amphipoda are undoubtedly fish. 

 As noted in the section on the economic importance of the group, 

 the Amphipoda form a very extensive source of food for many 

 of our most highly valued fishes. Even the shore-inhabiting 

 species, like Orchestia, frequently fall prey to Fundulus which 

 come with the tide into every place where there is enough water 

 to cover them and search for every possible material for food. 

 The xVmphipoda are usually in concealment when the tide is high 

 but when one leaves its retreat it forms a tempting morsel for 

 a fish. Besides fishes, the shore-inhabiting species must also be 

 destroyed by birds. Although this has never actually been 

 observed, forms of life far more active than the Amphipoda 

 have frequently been seen to be pursued by birds in the same 

 spots occupied by Orchestia and similar species. Miss Small- 

 wood also describes an encounter which she observed between 

 a half grown Orchestia palustris and one of the staphalinid 

 beetles, in which the latter was victorious. The spiders, which 

 occur in the same localities and occupy the same retreats as 

 individuals of this species, must also serve to keep down the 

 numbers. 



RESISTANCE TO ADVERSE CONDITIONS. 



The generally wide distribution of the Amphipoda may be 

 partly accounted for by their power of resisting unfavorable 

 environmental conditions. Many marine, as well as fresh-water, 

 forms are able to survive under conditions which are fatal to 

 almost all other groups. In examining material collected along 

 the shore, it is frequently noticed that after molluscs, actinians, 

 and worms decay, the Amphipoda still survive. 



Talorchestia, though not living in water normally, is dependent 

 nevertheless upon it, for when placed in perfectly dry sand, 

 specimens died in less than seven hours, while those placed in 

 partially moistened sand in the laboratory survived ten or twelve 

 days ; when the sand is kept completely covered with water, it 

 has been found that this species dies quite soon. Orchestia 

 palustris may remain submerged for days without fatal results 



