Hexagenia nymphs. Nymph of H. bilineata Say, dorsal view. The hind feet are turned forward for comparison with the other feet, and the gills on the right are moved aside to show the markings on the abdomen. The 3-branched, rudimentary gills on the first abdominal segment are abnormal
Pentagonia vittigera Walsh; adult. Adult mail of the quadripunctata form 15; Legs of one side 16; End of abdomen of male from beneath 17; End of abdomen of female from beneath 18
Hexagenia bilineata Say; adult. Adult male (segmentation of the tails omitted...) 1; Legs of one side, fore, middle, and hind from left to right... 2; end of the abdomen of the male from beneath, showing forceps, penes, and base of tails; middle tail rudimentary
