AQUATIC INSECTS IN NEW YORK STATE 303 
Figure 9 is still further cephalad and is taken at about the 
level n-o of figure 8, and shows the cuticular pocket entirely sep- 
arated from the body wall and the thick cuticular 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, while 
figure 7 shows the solid cephalic end of the cuticular 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 place. 
The trachea from each spiracle extends cephalad and mesad 
for a short distance, where they are united by a short trans- 
verse tracheal trunk [pl.28, fig.14¢tir]. From their dorsal and 
mesal angle extend pronounced cuticular 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, while 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 15t,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 cuticular pocket consists of long, fine 
and closely appressed plates or lamellae, which 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.15pf], 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.16], so that each cuticular 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 
cuticle forming the cuticular pocket lies apparently in a nat- 
