150 



HALF HOURS WITH INSECTS. 



[Packard. 



Fig. 114. 



dalns (Fig. 114), which transforms into the large net-veined 

 insect (Fig. 115) so formidable in appearance, and yet so 

 harmless. A singular chapter in biology would be the life 

 of this insect. The gigantic carnivorous larva, with its 



large head and enor- 

 mous jaws, is provided 

 with eight pairs of long, 

 rather stiff, respiratory 

 filaments. Dr. Ilagen 

 has called attention to 

 the spiracles of this crea- 

 ture, which are not usu- 

 ally present with tracheal 

 gills, and to the reason 

 for their existence. It 

 seems that like the Euro- 

 pean Sialis (Fig. 116, 

 larva and pupa) it lives 

 some weeks out of water 

 before its transformation 

 into the pupa, which 

 rests in an earthen co- 

 coon in the banks of 

 streams above water. 

 The eggs (Fig. 114, a) 

 are very large, and are 

 deposited In a squarish 

 mass on the steins of 

 water plants. 



There is no more beau- 



Corydalus larva and egg 



tifnl object for low powers of the microscope than the larval 

 May fly (Fig. 117). The body is so transparent that the 

 movements of the heart, the play of its valves, the circula- 

 tion of the blood, the distribution of the tracheae, the diges- 

 tive canal and its movements, as well as the action of the 



22 



