Packard.] INSECTS 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 cap 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 young 
May fly moves rap¬ 
idly and gracefully 
through the water. 
It lives two years, 
while the 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 Corydalus. 
23 
