"FLAT BUT NOT UNINTERESTING" 39 



mer. Shall we all admit that this is a wise provi- 

 sion of nature? If it were otherwise there might 

 be more stone-flies, but fewer trout suppers. 



When it becomes necessary for a stone - fly 

 nymph to move, it uses its six long legs and 

 makes very good headway. When at rest it clings, 

 with legs outspread, to the surface of the stone, 

 holding tight with its claws. Just back- of each 

 leg is a bunch of soft short hair, gray in color. 

 These tufts are the tracheal gills, by means of which 

 the creature obtains its air supply. The water flow- 

 ing constantly over the gills keeps them in con- 

 tact with fresh air. In another chapter the action 

 of the tracheal gills of aquatic insects is discussed 

 at some length. 



Happy the young stone-fly which, having escaped 

 the mouths of hungry trout and other enemies, ful- 

 fils its destiny. Many of them live to maturity if 

 we may judge by the number of cast skins found 

 on the banks of our swiftly flowing streams in 

 June. 



May their tribe increase ! 



