AQUATIC INSECTS IN NEW YORK STATE 303 



Figure 9 is still further ce])lialad and is taken at about the 

 level no of figure 8, and shows the euticular pocket entirely sep- 

 arated from the body wall and the thick euticular wall inclosing 

 the air passage on the dorsal side and its almost complete thin- 

 ning out on the ventral side to allow for the entrance of the 

 trachea. Figure 12 represents the air passage as crowded still 

 farther on to the ventral side by the thick chitinous walls, wiiile 

 figure 7 shows the solid cephalic end of the euticular pocket and 

 the tracheal trunk almost completely separated from it, with 

 three thick bands of muscles near the ventral end of the trachea 

 which extend to the dorsal apodeme and the body wall and are 

 effective in holding the trachea in i)lace. 



The trachea from each spiracle extends cephalad and mesad 

 for a short distance, where they are united by a short trans- 

 verse tracheal trunk [pi. 28, fig.l4#fr]. From their dorsal and 

 mesal angle extend pronounced euticular thickenings, from 

 which muscles extend to the dorsal apodeme, da, and other 

 muscles in turn extend from the apodeme to the body wall. 

 From the common union just described there extends on either 

 side as far as the head a single tracheal trunk, which is ovate in 

 outline in transection, the long diameter being seven or eight: 

 times the short diameter, wdiile the taenidia are long and greatly 

 thickened and are arranged like a series of parallel rods along- 

 each face of the trachea. This arrangement of the taenidia and 

 shape of the trachea permit its being expanded and used as a 

 reservoir for storing the air between air-taking periods. The 

 taenidia are shown in transection on plate 27, figure 15f, which 

 is a section across the short diameter of the trachea, and in 

 surface section by figure 16^ The tracheal trunks extending 

 from the large lateral trunks to the spiracles of the other seg- 

 ments are of the ordinary type, cylindrical and with fine spiral 

 taenidia. 



The cuticle forming the euticular pocket consists of long, fine 

 and closely appressed plates or lamellae, w^hich seem to be 

 intracellular in origin. In specimens stained in borax carmine 

 it is possible to trace fine branches of the protoplasm of the 

 cells extending in between the lamellae throughout their entire 

 length [pl.28, fig.lT)/)/], and, when these plates are examined 

 under a high power of the microscope, it is found that there 

 is an anastomosing of the protoplasm of the adjacent branches 

 [pl.28, fig.lfi], so that each euticular area is surrounded on all 

 sides by protoplasm. 



When cross sections at the caudal end of the spiracle of the 

 eighth abdominal segment are examined, it is found that the 

 €uticle forming the euticular i»ocket lies apparently in a nat- 



