MAY-FLIES IN FALL BROOK 75 



other kind of water insect, except the stone-fly 

 nymphs. After a little careful observation one 

 learns to distinguish the two. The young May- 

 fly gets about by the aid of six stout legs, which 

 may, on occasion, be used oar-fashion. Behind 

 the legs are pairs of fringed gills, through whose 

 walls the air is mixed with its pale blood. Still 

 further back, at the very end of the body, are two 

 or three long appendages, thread-like or feathery. 

 These appendages are the only feature in which 

 the young resemble their winged parents, or give 

 any suggestion of what they shall be. No indi- 

 cation of wings appears on the creature until after 

 several molts have taken place. 



It is a general rule that insects never change 

 their skins after reaching the adult form. They 

 cease to grow after attaining wings and molting 

 is no longer necessary. In the May-fly we have 

 an exception to this rule. When it leaves the 

 water and sheds the skin it wore as a true nymph, 

 it leaves behind its gills and hungry jaws. It is 

 able to fly rather awkwardly and joins thousands 

 of its brothers and sisters and cousins in a search 

 for some suitable place to undergo its final molt. 

 Sometimes the sides of buildings and the trunks 

 of trees on the banks of the streams are covered 

 with the frail bodies, especially early on a summer 

 morning. 



The last molt is accomplished very quickly and 

 the cast skins are extremely thin and delicate. The 

 creatures which emerge are the gauzy May-flies 

 which so richly deserve the poets' praises. They 



