1. Anal gills present (Fig. 2.1.4.1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Anal gills absent (Fig. 2.1.4.2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Abdomen uniformly dark (Fig. 2.1.4.3) . . . . . . . . . . Acroneuria abnormis (in part)
Abdomen variously patterned in lateral light and dark bands (Fig. 2.1.4.4). . . . . . . . . . 3
3. Posterior margin of abdominal tergites margined by dark markings (Fig. 2.1.4.5). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acroneuria carolinensis
Posterior margin of abdominal tergites margined by light markings (Fig. 2.1.4.6) . . .4
4. Light M-shaped band anterior to median ocellus (Fig. 2.1.4.7); light areas on abdominal tergites varying from almost all dark to light, except for 2 detached lateral dark areas (Fig. 2.1.4.8). . . . . . . . . . . . . . . . . Acroneuria abnormis (in part)
Three light spots anterior to median ocellus (Fig. 2.1.4.9); light areas on abdominal tergites bandlike and parallel, with dark bands (Fig. 2.1.4.10) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acroneuria internata
5. Posterior margin of abdominal tergites margined with dark markings (Fig. 2.1.4.11) . [also see couplet 8]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acroneuria lycorias
Posterior margin of abdominal terga unpigmented (Fig. 2.1.4.12). . . . . . . . . . . . . . 6
6. Dark abdominal bands of approximately equal width across tergite (Fig. 2.1.4.12); in some specimens lighter coloring invades posterior margin of dark ocellar triangle (Fig. 2.1.4.13) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acroneuria frisoni
Note: Most literature up to and including Poulton and Stewart (1991), treated this species as Acroneuria evoluta. See discussion below under A. evoluta.Dark abdominal bands expanded posteriorly near median line; ocellar triangle completely dark (Fig.2.1.4.14). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Dark abdominal bands decrease in width laterally, median expansions of dark bands not reaching posterior margin of tergites (Fig.2.1.4.14). . . . . . . . . . Acroneuria perplexa
Dark abdominal bands not decreasing in width laterally, median expansions of dark bands commonly reaching posterior margin of tergites, thus causing light posterior margin to be broken into 3 spots . . . . . . . . . . . . . . . . . . . . . . . . Acroneuria filicis
8. An irregular, light, M-shaped band on head anterior to median ocellus; posterior half of abdomen banded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acroneuria lycorias
No light, M-shaped band on head anterior to median ocellus but 3 lighter spots anterior to it; abdomen uniformly dark . . . . . . . . . . . . . . . . . . Acroneuria evoluta*
*Throughout the history of this name, it was associated with a small Acroneuria relegated to small and medium streams. The true A. evoluta is a large, large river species. Frison (1942) described the large river species under the name A. mela. Stark and Brown (1991) described the small river species under the name A. frisoni and synonomized A. mela with A. evoluta.Note: Acroneura kosztarabi (Kondratieff & Kirchner, 1993) has been reported for Ohio (DeWalt, et al., 2012) but the nymph is not described. Acroneuria evoluta is also reported for Ohio (DeWalt, et al., 2012), but this has been renamed Acroneuria frisoni (Stark & Brown, 1991). Acroneuria covelli is also reported for Ohio, along the Ohio River, but the nymph is unknown (Grubbs & Stark, 2004).
Key to the Genera of Ohio Acroneuria Nymphs
