AQUATIC COCKROACHES. 3 
their bonds had to be tightly fastened in order to keep them in 
position ; even then the prisoners did not relax their efforts to 
free themselves, and I believe that they died of exhaustion and of 
injuries sustained in their struggles rather than from drowning. 
The aquatic species, on the other hand, remained comparatively 
quiet ; the reversed specimens, being fastened in a position more 
or less natural to them, and being able to obtain their supply of 
air in quite a normal and usual manner, were very little dis- 
Fic. 1.—End of abdomen of a larva of Rhicnoda natatrix, sp.n., dorsal 
view; s.p. spiracular tube; c. cercus; s.a.l. last dorsal tergite. 
Fic. 2.—The same, ventral view; st. abdominal sternite; s. spiracle ; 
¢. abdominal tergite. 
Fie. 3.— Spiracular tube, highly magnified, seen in optical section ; 
v. vestibule; s. spiracle; m. muscle working 0., the chitinous bow; t. 
trachea. 
tressed by their bonds, and the other specimens were soon reduced 
to a comatose condition by the difficulty of obtaining air. The 
terminal spiracles of these aquatic Cockroaches are situated at 
the base of two tubes visible on the dorsal side projecting from 
below the seventh tergite, and external to the anal cerci (fig. 1). 
