134 MARINE AND FISHERIES 



5 GEORGE v., A. 1915 



Key to Nymphs. 



A. Gil's oblong, Group I. 



B. Nymphs entirely brown without a distinct dorsal colour pattern. 



c. An inverted dark U-shaped mark on ventral surface of 9th segment and 

 a dark spot on ventral surface of 8th. Dorsal surface of body has a 



smooth appearance '. H. fiavescens. 



CC. A row of dark mushroom-shaped marks along ventral surface and a 

 rectangular dark mark on 9th. Dorsal surface has a rather granular 

 appearance and lateral margins of body quite hairy. H. rubromaculata. 

 BB. Nymphs not entirely dark brown and have a distinct colour pattern, 



D. Ventral surface of abdominal segments banded with dark bands 

 along posterior margins. 



E. Broad dark bands at posterior margin of each segment on dorsal 



surface H. f usca. 



EE. Dark bands at posterior margins of segments 7, 8, 9, and 10, 

 not as broad as preceding species and a more elaborate colour 



pattern H. lutea . 



DD. Ventral surface not banded. 



p. Two rows of black dots along ventral surface of abdomen. 



H. luridipennis. 



PF. No dots H. luridipennis. 



AA. Gills oval and pointed, Group II. 



G. Two light longitudinal stripes on dorsal surface of abdomen close to 

 median line. 



H. Stripes fairly uniform for entire length. Reddish species. . H. canadensis. 



HH. The stripes not of uniform width, very wide on 8th segment, 



very narrow on 5, 6, and 7 so that darker intermediate parts have 



oval shapes. Lighter species H. frontalis, 



GG. Dorsal surface of abdomen has appearance of 3 longitudinal dark stripes. 



Colour greenish yellow H. (undetermined species) . 



Mr. Nathan Banks kindly identified the imagos for me so far as possible. 



Description of Species. 



Heptagenia flavescens Walsh. 



(PI. XV, Figs. 4-5). 



Male imago (Description taken from Monograph of Eaton, '88) : 



Measurements: Body 9 4- mm.; wings 11+ mm.; setae 27-38 mm. 

 Yellowish. Eyes bright greenish yellow during life. Notum ferruginous, 

 sometimes verging upon piceous. Dorsum of abdomen ferruginous, darker at 

 the tips of segments 2-7 and with a pair of subobsolete pale vittae at the base of 

 each of them; venter pale greenish in segments 2-7 or 8. Setae whitish; the join- 

 ngs fuscous. Fore leg pale ferruginous with a median and a terminal band on the 

 femur, the tip of the tibia and the tarsal joinings and tips fuscous. Hinder legs 



