THE CANADIAN ENTOMOLOGIST 165 



near rapids. Exuviae are often found on precipitous rocks rising 

 •out of the water from a depth of 8 or 10 feet. 



Nymph (figs. 15-17) short-legged and somewhat stouter than 

 most Corduhine nymphs Head broadly convex above and on the 

 sides, eyes not very prominent, frontal ridge with a scurfy pubes- 

 cence, the anterior margin convexly curved, hind angles of head 

 prominent, distance between them a little greater than half the 

 greatest width of the head; hind margin distinctly excavate. 



Labium extending very slightly behind the bases of the front 

 legs; mentum somewhat broader at the distal margin than long, 

 the middle lobe somewhat abruptly deflexed, bluntly obtusangu- 

 late; mental seta? 9-11, the innermost 3 or 4 much smaller than the 

 others; lateral lobes triangular, their distal margins produced into 

 se\-en semi-elliptical teeth; lateral seta 6; movable hook very 

 slightly arcuate. 



Marginal ridge of pronotum produced on each side behind the 

 ]iosterior angles of the head as a prominent process, which is some- 

 Avhat smaller than the very prominent supra-coxal processes. 



Legs short, the length of hind femora being slightly less than 

 the width of the head. 



Abdomen ovate, its greatest breadth at segs. 6 or 7, slightly 

 .■greater than two-thirds of its length ; curve of the lateral margins 

 somewhat stronger in the distal than in the proximal half; lateral 

 spines on 8 and 9, in each case about one-third to one-half as long 

 .as the corresponding segment, those on 8 strongly divergent, on 9 

 parallel and extending caudad scarcely or not at all beyond the tips 

 of the appendages. 



Dorsal surface rather strongly convex, dorsal hooks present 

 on 1-9, those of the basal segments slender, nearly erect and slight- 

 ly hooked, becoming gradually broader and lower caudad, and, on 

 7-9, reduced to scarcely more than a short ridge. Superior ap- 

 pendage triangular, equilateral, very slightly shorter than the some- 

 what divergent inferior appendages and somewhat longer than the 

 lateral appendages. 



Colour yellowish or orange-brown, variegated with dark- 

 brown. Head dark brown above, generally somewhat paler in the 

 ■centre and on the frontal ridge. Thorax and wing-cases varie- 

 gated with pale and dark markings, femora and tibiiT? dark, with 



