Packard] INSECTS OF THE POND AND STREAM. 155 



Fig. 123. 



of the muscles of the body shows their wonderful adapta- 

 bility for the production of these complicated movements. 



Many aquatic insects are either "side wheelers" or pro- 

 pellers. The larval Ephemera, aided by the beautiful pad- 

 dle-like tracheal gills 

 along the sides of the 

 body, moves through 

 the water b}' a series 

 of exceedingly grace- 

 ful undulations ; while 

 the young Agriou pro- 

 pels itself, partly at 

 least, by its large 

 terminal respiratory 

 leaves. How by a 

 strange economy of 

 nature the dragon fly 

 larva combines the 

 functions of digestion, 

 locomotion and respi- 

 ration in an organ 

 which like a force 

 pump ejects a power- 

 ful stream, and like 

 a flash propels the 

 creature many times 

 its own length over 

 the bottom of its 

 pond, we have seen 

 above. 



One important result of the metamorphosis of the 3'oung 

 mosquito into a pupa is that it is promoted from a wriggler 

 to a paddler, padilling being a higher mode of aquatic loco- 

 motion. Our figure of the pupal mosquito shows in a rude 

 way the two beautiful, thin, rounded paddles at the end of 



27 



DijilMx larva; x, mass of trachere. 



