Aquatic Adaptations of Insect Larva 277 



parallel the method of Ranatra mentioned above in 

 that they have developed a long respiratory tube, 

 capable of reaching the surface of the water while they 

 remain far below. 



FIG. 170. Tracheal gill of the mayfly nymph, Heptagenia, show- 

 ing loops of tracheoles toward the tip. 



Of those that breathe the air that is dissolved in the 

 water a few lack gills even when grown to full size ; but 

 these for the most part live in well aerated waters, and 

 possess a copious development of tracheae in the thinner 

 portions of their integument. Such are the pale 

 nymphs of the stonefly, Chloroperla, that live in the 



