WATER INSECTS AND THE RISE 81 



which turned out to be an Iron Blue in its sub-imago 

 state, and the first I had seen that season. Hastily putting 

 one on my cast, I secured a fish at my first throw, and 

 although the rise only lasted some twenty minutes longer, 

 I caught seven other fish. When the rise ceased there 

 existed a big hatch of Iron Blue in the air, but the few 

 solitary rising fish took no further notice of the Iron Blue 

 Duns, which rapidly disappeared. I tried it, however, for 

 some time longer, but eventually I replaced it with my 

 Grannom, and creeled several other trout before going home. 



Before putting on the Grannom, however, I examined the 

 food in the latest caught fish, and found that the upper part 

 of its gullet contained a great number of nymphae or pupae 

 of the Iron Blue in their most advanced stage, several 

 specimens having their wings already unfolded. 



I am inclined, therefore, to think that, owing to some 

 alterations of the meteorological conditions, the pupae of 

 this Ephemeridae, moved by one of those mysterious impulses 

 which occasionally influence the insect world, had risen to 

 the surface to assume their sub-imago existence, and that 

 this general movement was the cause of the trout leaving 

 the Grannon in favour of the Iron Blue. 



Since that occasion I have corroborated the theory I then 

 formed by examining the food of the fish caught during a 

 sudden rise, and have found that it consists, as a rule, of a 

 greater number of the pupae than the sub-imago of the 

 existing hatch. I have also noticed the trout during a rise 

 taking the pupae below the surface, and have seen the trout 

 following pupae up, and taking them just as they reach the 

 surface of the water. 



I do not claim that this suggestion will account for all the 

 general rises peculiar to trout, but I think that in many cases 

 it can be proved to be due to some initial movement of the 

 pupae towards their next metamorphosis. A few heavy 



