THE INSECT FOOD OF TROUT 161 



of Whirligig beetle, Orectochilus Villosis. This 

 latter beetle is nocturnal. My friend says that he 

 has often thought, on quiet summer evenings, when 

 he could hear fish sucking something in preference 

 to his fly, that it was this beetle which attracted 

 them. 



Several species of Helephorus are abundant, and 

 no doubt form a constant food supply in the 

 neighbourhood of water vegetation. 



The larvae of the Alder Fly (Sialis) abound. 



Many species of Chironomidae and Tanyphus are 

 plentiful in the mud and on plants. 



The larvae of the Sand Fly (Simulium) is 

 plentiful in the shallow streams of both the river, 

 and becks, where the water is constantly on the 

 move over beds of weeds. 



In all the streamy parts of the river, and becks, 

 the larvae of the Stone-fly (Perla) is grossly 

 abundant, and provides, during April and May, an 

 enormous supply of rich food. 



