452 Mr. Newport on the Anatomy and Affinities of Pteronarcys regalis. 



{Capnia vemalis), but it is not so numerous. It pairs in the crevices of 

 decaying ice. The male has long antennae, 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 (b). 



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 branchiae {b, b, b), and 

 the sternal orifices {f, g, h). 



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 tracheae from the second spiracle giving off branches to the wings, 

 and others across the body, {k) a branch from the second, and [T] one from the 

 third spiracle, (tw) oesophagus, (w) the crop, (o) gastric caeca, {p) stomach, 

 {q) iUum, {r) the Malpighian vessels, («) colon, {t) rectum. 



Fig. 11. Termination of one of the lateral tracheae. 



Fig. 12. Alimentary canal in Perla. 



Fig. 13. Alimentary canal in Sialis. 



Fig. 14. Nervous system : (m, v, w) entofurca, {x) testis and duct, (y) vesiculae 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. 



