452 Mr. Newport on the Anatomy and Affinities of Pteronarcys regalis. 
(Capnia vernalis), but it is not so numerous. It pairs in the crevices of 
decaying ice. The male has long antennz, and his wings are generally 
rumpled, as if glued together. I believe he seldom takes wing." Mr. Barn- 
ston tells me that he has seen this insect coming up between the crevices of 
the ice. 
DESCRIPTION OF PLATE XXI. 
Fig. 1. Imago of Pteronarcys, male :—of the natural size. 
Fig. 2. Pupa of Pteronarcys, male :—of the natural size. 
Fig. 3. Branchial tuft, showing the trachea within it (a) and its mode of distribution (à). 
Fig. 4. Branchial filament (c, d, e), showing the direction of the current of blood. : 
Fig. 5. Inferior surface of Pteronarcys, showing the situation of the branchiz (b, 6, b), and 
the sternal orifices (f, g, A). ; 
Figs. 6, 7, 8. Left prothoracic spiracle: (6) closed, (7) partly open, (8) fully open. 
Fig. 9. One of the abdominal false spiracles with trachea. : 
Fig. 10. Diagram of the body, with the internal respiratory organs and alimentary canal: 
(i) bundle of trachez from the second spiracle giving off branches to the wings, 
and others across the body, (5) a branch from the second, and (I) one from the 
third spiracle, (m) cesophagus, (n) the crop, (0) gastric caca, (p) stomach, 
(g) ilium, (r) the Malpighian vessels, (s) colon, (¢) rectum. 
Fig. 11. Termination of one of the lateral tracheze. 
Fig. 12. Alimentary canal in Perla. 
Fig. 13. Alimentary canal in Sialis. | 
Fig. 14. Nervous system: (v, v, w) entofurca, (x) testis and duct, (y) vesicule seminales, 
! (z) ductus ejaculatorius and penis. 
Fig. 15. Testicular follicles, 
. Fig. 16. Inferior surface of the abdominal segments in the male. 
Fig. 17. Inferior surface of the abdominal segments in the female. 
