



A THEORY 89 



question. The number of insects living in 

 fresh waters, and possessing the power of 

 moving through it, is enormous. 



There are between 220 and 230 different 

 species of Water Beetles in our waters. 

 There are also very many different sorts 

 of Heteroptera, including the numerous 

 family Notonectidse. When we add to 

 these the larvse of flies and water beetles, 

 the Crustaceans, Hydrae and Water 

 Spiders, we must begin to realise that 

 there are other things than a drowned 

 natural fly for which the fish might mis- 

 take its imitation, with the materials of 

 which it is made soaked in and drawn 

 through the water. 



The movement of many of these crea- 

 tures through the water is fairly repre- 

 sented by the movement of the artificial 

 fly in wet fly-fishing ; and, when the shade 

 and colour and size of the fly is the same 

 as one of these aquatic creatures, I am sure 

 that the fish takes it, not for a fly, but for 

 one of them. Again, when the enormous 

 number of these aquatic creatures is con- 

 sidered, it is most probable that one or 

 other of the flies tried on any water by 



