234 THE DRY-FLY MAN'S HANDBOOK 



When the nymph is ready to undergo the change 



to a winged insect examin- 



Subimago. ation with a lens will show 



its wings folded up within 

 the two dark excrescences or wing-covers on the back 

 of the thorax. It will also be seen that inside the 

 nymphal skin there is visible the form of the winged 

 insect, its head, thorax, body, legs, and tail perceptibly 

 of more slender proportions than in the nymph. The 

 swimming nymph (Fig. 40) shows this very well. 



The digging and swimming nymphs swim up 

 through the water, arriving at the surface and there 

 splitting open the outer skin at the back of the 

 thorax. The thorax and head are first pushed up 

 and out, then the legs struggle out, the body and 

 setae being partly worked out almost at the same 

 time. Next the wings are unfolded and withdrawn 

 from their covers one at a time, and, lastly, the body 

 and setse are drawn forth. The subimao-o then rests 

 on the cast nymphal skin until its wings are dry, 

 when it flies ashore to shelter on the grass, rushes or 

 boughs. The crawling nymphs effect the change to 

 the subimago in a similar manner, but the flat nymphs 

 require a dry spot, to which they attach themselves 

 for the process of metamorphosis to the subimago. 

 Their nymphal shucks are often found adhering to 

 the stones on the river-bank. 



Subimago is the term applied by modern ento- 

 mologists to this stage in the life of the Ephemeridse, 

 and the students of old books on the subject must not 



