Affinities of Pteronarcys regalis. 433 
places. This also appears to be the habit of other species of the genus as 
well as of Pteronarcys regalis. Mr. Gosse; who first figured the latter spe- 
cies in his ‘Canadian Naturalist, informs me that he has taken P. Proteus 
and another smaller species in Lower Canada, at Sherbrooke, where the 
Magog river forms a waterfall of considerable height, on the rocky sides of 
which, constantly washed by the spray, he has found P. Proteus in great num- 
bers, hanging to the sides, or concealed in the crevices of stones and rocks, 
and that he has but very rarely taken it on the banks of other parts of the 
. river. -The Pteronarcys thus resembles an amphibious animal in its habit of 
life, and may be designated,—if I may be allowed the term,—an Insect Proteus 
among the winged Articulata,—the representative in structure, as it appears 
to be in habit, of the Proteus of Vertebrata. Its organs of respiration fully 
justify us in instituting this comparison. The true Proteus has both lungs and 
branchiz, and a similar conformation of structure exists in Pteronarcys, in so 
far as the ramified tracheæ being the direct recipients of atmospheric air, are 
to be regarded as the representatives of lungs. 
Sternal Orifices and Endo-skeleton.—In the short notice viéih I formerly 
published on this singular insect *, I pointed out the existence of three pairs 
of orifices in the tegument of the sternal surface of the thoracic segments 
(fig. 5 f, g, h), one pair in each segment, between the insertions of the legs, 
precisely analogous in situation to the respiratory orifices in Julus and some 
other Myriapoda. But as these orifices had not then been traced to their 
termination within the body, and as their situation in the segments was of 
doubtful indication in a hexapod insect, no conclusion could be drawn from 
the mere fact of their existence as to whether they had or had not any com- 
munication with the tracheze. I have now examined them carefully, and find 
that they pass into the thorax as strong, bone-like tubes, diverging from the 
axis to the periphery of the body, in the immediate vicinity of some of the 
principal tracheze, but that they do not in any way communicate with them, 
as they terminate abruptly as cæcal structures. They are, in fact, intus- 
suscepted parts of the hardened tegument, —organs of support, —which in most 
other insects are solid. They are the ento-thoracic portions of the sternal 
plates in each segment (fig. 14), the ante-furca (u), meso-furca (v), and meta- 
 * Annals and Magazine of Natural History, Jan. 1844, p. 23. 
312 
