THE CANADIAN ENTOMOLOGIST 251 



EE. Dark bands at posterior margins of 

 segments 7, 8, 9 and 10; not as 

 broad as preceding species and a 

 more elaborate colour pat- 

 tern H. liitea. 



DD. Ventral surface not banded. 



F. Two rows of black dots along 

 ventral surface of abdo- 

 men H. tri punctata. 



FF. No dots H. liiridipennis , 



AA. Gills oval and pointed. Group 2. 



G. Two light longitudinal 

 sfripes on dorsal surface 

 of abdomen close to me- 

 dian line. 



H. Stripes fairly uniform 

 for entire length. 

 Reddish species 

 . . . .H. canadensis. 



HH. The stripes not of uni- 

 form 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 three 

 longitudinal dark stripes. 

 Colour greenish yellow. 

 H., sp. undetermined. 



Mr. Nathan Banks kindly identified the images for me and 

 loaned me specimens of Heptagenia verticis, H. luridipennis and 

 H. terminata, for comparison. 



