THE EPHEMERID>E. 65 



existence, and swim to the surface. When there the mask-like 

 membrane, under which the wings, etc., have been visible, 

 see Figs. I and 2, Plate XV., splits open, and, supported on 

 this shell as on a raft, the insect gradually frees every part 

 of its body and unfolds its wings. As soon as these wings 

 are dried, and the body is clear of its shell, the sub- 

 imago, as it is now called, flies to the nearest bank, where 

 it shelters itself amid the grasses, leaves, etc. It is commonly 

 known in this state as a Dun, and it appears at various 

 times, when the weather is favourable, in the vicinity of the 

 water during a period of from one day to two or more 

 weeks, flying with the breeze, generally down stream. In 

 this stage of its life it can be easily recognised by its com- 

 paratively heavy flight, its dull semi-opaque appearance, and, 

 by the aid of a watchmaker's glass, some cilia will be seen 

 covering the surface and forming a fringe to the posterior 

 margin of its wings. 



The sub-imago stage of its life, which is very brief in 

 some cases, is finally forsaken, when the entire membrane 

 of its body and wings again splits off, and it then assumes 

 its perfected stage as the imago or spinner. 



It is now fully matured and enters into its bridal existence, 

 which lasts but a few days. In this stage it is to be seen 

 in great numbers where the heat is not excessive, and during 

 the evening hours. Its wings are now gauzy, and its body 

 lighter and more brilliant in colour. It is easily recognised 

 as it soars, floats and sinks in the ambient summer atmosphere. 



D.P. P 



