216 ANCIENT ANGLING AUTHORS 



a nymph when the rudiments of the wings have 

 appeared) into the sub-imago, with that given by 

 Bowlker. When this change is ready to take place, 

 the nymph " swims upwards through the water, and, 

 if it has calculated its movements accurately, arrives 

 at the surface just before the metamorphosis. Its 

 entire body is inflated, and the external integument 

 distended, until at length it splits along the back of 

 the thorax. First the thorax, then the head, is pushed 

 out through this slit in the outer skin. Then the legs 

 are disengaged, and next, just before the abdomen 

 and setae are quite free, the wings, one at a time, are 

 withdrawn from their covers and quickly unfolded. 

 The winged insect supports itself on the cast nymphal 

 skin or on the water until its wings are dry, and then 

 flies ashore to seek the friendly shelter of grass, rushes, 

 sedges, or even trees " (Dry Fly Entomology, Halford, 

 1897). 



In the sub-imago stage, the fly is enveloped in a 

 thin membrane or skin, which has to be cast off 

 before it becomes a perfect or fully developed fly 

 the imago. The metamorphosis from the sub-imago 

 to the imago is effected by casting off the skin by a 

 process very similar to that by which the larva casts 

 off its shuck, when changing to the sub-imago. 



The fly is now known to live longer than its 

 formerly allotted span of five hours. Mr Halford has 

 kept them alive for five or six days. 



In 1774, a second edition of Bowlker's Art of 

 Angling appeared, edited by Charles Bowlker, the 



