1. Abdominal terga with paired submedian tubercles or with paired submedian protuberances, tubercles or protuberances always discernible on segments 4-7 (Fig. 1.1). . . . . . . . . . . . 2
Abdominal terga without tubercles or protuberances (Fig. 1.2). . . . . . . . . . . . . . . . . 5
2. Abdominal terga with moderately long, sharp, paired submedian tubercles on segments 2- 8 (Fig. 1.3, Fig. 1.3a); foreleg femur dark with pale band across central width; foreleg tibia and tarsis dark with large pale spots (Fig. 1.4). . . . Ephemerella needhami
Abdominal terga with variable paired submedian tubercles, tubercles absent on tergum 1; (Fig. 1.55) foreleg femur pale with dark mottled bands; foreleg tibia and tarsis pale with dark band across them (Fig. 1.7). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Abdominal terga with moderately long, sharp paired submedial tubercles on segments 2- 9 (Fig. 1.8); tibial and tarsal bands dark brown to black (Fig. 1.9); head with small submedian occipital tubercles (from direct frontal view). . . . . . . .Ephemerella subvaria
Abdominal terga with variable paired submedial tubercles; tibial and tarsal bands lighter than above or absent (Fig. 1.11); head without tubercles or with minute tubercles (Fig. 1.12). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Abdominal terga with paired submedian tubercles on segments 2-9, tubercles small but discernible on terga 3-8, barely discernible on terga 2 and 9 (Fig. 1.13); fore fermora with a moderately wide band of subapical spines (Fig. 1.14). . . . . . . .Ephemerella rotunda
Abdominal terga with paired submedian tubercles on segments 3-8 (rarely small tubercles on 2), tubercles small but discernible on terga 4-7 barely discerible on terga 3 and 8; forefemoral spines variable. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ephemerella invaria
5. Caudal filaments unicolorous, without brown bands . . . . . . . . Ephemerella excrucians
Caudal filaments with alternating pale and brown bands (Fig. 1.15). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ephemerella dorothea
Key to Ohio Ephemerella Nymph Species
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