and, Classification of Rhynchota. 241 
cover outside the spiracle. It is easy to see the importance of 
these arrangements for the respiration of the Nepe. ey 
come to the water flying, no doubt after long-continued search, 
and with the walls of the thorax violently distended by the 
tropical animals. : 
The third pair of spiracles is placed on the back of the 
animal, hidden by the wings, between the metanotum and the 
first dorsal segment of the abdomen. It has hitherto only been 
observed in Nepæ, as stated above, but exists really in all 
Heteroptera. tt is large, and those who are sufficiently con- 
versant with the structure of spiracles will not fail to see it; 
but others will easily be deceived by the various membranes 
which are placed between the places of insertion of the wing- 
muscles and the roots of the ribs of the wings. This is the 
pair which I have called spiracula metathoracica in Eleutherata, 
giving to the two anterior pairs the names respectively of 
the metathorax covers, in many trochalopodous bugs, as we 
