LIFE IN PONDS AND STREAMS 



combs on their mouth-parts and using these as diatom rakeS 

 they can pull in a good harvest. 



Amid the jostling water of rapids small animals find safety 

 only by holding on, by getting under cover, or by being small 

 or slender or flat (PI. III). Flattest of any of this society 

 are the water pennies (Fig. 215) which cling motionless to 

 the under surface of the rocks, smooth-backed and copper- 

 colored, looking like small pennies but not at all like the 

 young beetles that they really are. 



Waterfalls. — In springtime the rocks of waterfalls are green 

 with algae, but later the water mosses Fontinalis and Hygro- 

 hypnum often crowd in and cover them. These grow on the 

 straight rock face, well under the waterfall, escaping the dash 

 of the water but kept wet by constant tricklings. Here 

 small clamberers hide among the leaves — case-bearing caddis 

 worms and beetle and midge larvae. Midges swarm above 

 the falls and lay their eggs in little white skeins upon the 

 wet rock. Adult midges emerge from the waterfalls by 

 hundreds, and the fly-catching phoebe on the branch above 

 gets a plentiful harvest from the air. Large falls are forag- 

 ing places for swallows which collect the emerging mayflies; 

 even at Niagara they swing into the mist and spray, and 

 when they dart out again their mouths are whiskered with 

 protruding mayflies. 



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