230 THE DRY-FLY MAN'S HANDBOOK 



As they grow they shed their skins, and adolescence 

 is evidenced by the advancement towards maturity of 

 the reproductive organs internally and externally by 

 the outgrowth of rudimentary wings from the hind 

 borders of the proper segments. 



In 1843 F. J. Pictet, Professeur de Zoologie et 



d'Anatomie Comparde a I'Aca- 



Pictet's " Monograph." ddmie de Geneve, published 



his great "Monograph" on 

 the Ephemeridse. He classified the nymphs in four 

 divisions : Digging, flat, swimming and crawling — or 

 in his own language — Larves fouisseuses, Larves plattes, 

 Larves nageuses and Larves rampantes. In his time 

 entomologists gave the name larva to the wingless, 

 and the name nympha to the wing-budding grades of 

 the immature insect. Modern entomologists desig- 

 nate all the subaqueous stages in the development of 

 the young Ephemeridse after emergence from the 

 eggs as nymphcs. 



Very possibly, too, Pictet's classification of the 

 nymphs may not be quite orthodox according to the 

 ideas of the modern exponents of the science, but for 

 the fisherman they are not only descriptive of their 

 habits, but eminently useful for his rough-and-ready 

 process of identification. 



The digging nymphs, among which the immature 

 mayflies are included, corn- 

 Digging nymphs. mence digging out burrows or 



tunnels to form their habita- 

 tions as soon as they are hatched. Plate XV shows 



