Packard.] IXSECTS OF THE POND AND STREAM. 151 



muscles controlling 

 the jaws and other 

 parts of the mouth, 

 can all be watched 

 with ease. The tra- 

 cheal gills, like pad- 

 dles, either round or 

 long and leaf-like, 

 are arranged in pairs 

 along the hinder re- 

 gion of the body, 

 and the" tracheae in 

 them can be readily 

 seen. These beauti- 

 ful respiratory leaves 

 are also paddles, and 

 by their aid as well as 

 by the undulations of 

 the body the 3'oung 

 May fly moves rap- 

 idly and gracefully 

 through the water. 

 It lives two years, 

 while tbe winged fly 

 (Fig. 118) but a day, 

 rarely over twenty- 

 four hours. The 

 winged fly throws 

 off the pupa skin in 

 an instant. While 

 holding a pupa in 

 my hands the im- 

 ago slipped out sud- 

 denly with wings 

 fully formed. This 



Fig. 115. 



The Horned Corydulus. 



23 



