1. Abdominal sternum 9 larger than 8 and produced over part of sternum 10; tergum 10 cleft or entire, if entire, paraprocts often sclerotized or modified as hooks . . . . . . . . . . . . . . Males (2)
Abdominal sternum 8 larger than 9; tergum 10 and paraprocts unmodified . . . . . Females (6)
2. Male tergum 10 entire or slightly notched but without epiproct housed in notch; paraprocts usually sclerotized or modified as hooks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Male tergum 10 deeply cleft with lataeral margins modified a s hemiterga and epiproct hoursed within cleft; paraprocts unmodified . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Abdominal sternum 8 with conspicuous lobe . . . . . . . . . . . . . . . . . . . . . . . . . . Clioperla clio
Abdominal sterna lacking ventral lobes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Isoperla
4. Epiproct complex with lateral stylets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Epiproct complex without lateral stylets . . . . . . . . . . . . . . . . . . . . . . . . . Diploperla robusta
5. Suture lines behind ocelli dark but interrupted mesally by pale pigment; epiproct apex covered with thick, red brown setal spines; forewing length at least 18 mm . . . Malirekus cf. iroquois
Suture lines behind ocelli no darker than background pigment; epiproct apex variously armed but witout thick, red brown setal spines; forewing length less than 15 mm. . . . . . . . . . .Cultus
6. Y-arms of mesosternum absent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Diploperla robusta
Y-arms of mesosternum present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Subgenital plate extends less than halfway across sternum 9. . . . . . . . . . . . . . . . . . . . . . . . . 8
Subgenital plate extends at least halfway across sternum 9 . . . . . . . . . . . . . . . . . . . . . . . . . .9
8. Dark pigment on head forming Y-pattern with stem anchored on occiput behind ocelli and arms extending to antennal bases; area forward of medial ocelus with additional dark pigment that fuses with Y-pattern near median ocellus but leaves a small pale triangular enclosure forward of ocellus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Clioperla clio
Head pattern variable but without Y-pattern and enclosed pale triangle as above . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Isoperla (in part)
9. Subgenital palte usually notched, truncate or emarginated . . . . . . . . . . . . . . . . . . . . . . . . . 10
Subgenital plate usually rounded or triangular . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
10. Membranous folds at base of subgenital plate lie parallel to lateral margins of sternum 8; egg circular in cross section and usually with one or more large concavities; forewing length usually less than 15 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Isoperla(in part)
Membranous folds at base of subgenital plate angled from plate base toward center of sternum 8; egg triangular in cross section; forewing length 13-21 mm; usually at least 16 mm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Malirekus cf. iroquois
11. Membranous folds at base of subgenital plate lie parallel to lateral margins of sternum 8; egg generally circular in cross section, not turtle shaped . . . . . . . . . . . . . . . . Isoperla (in part)
Membranous folds at base of subgenital plate angled toward center of sternum 8; egg turtle shaped. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cultus
Key to the Adult Perlodidae of Ohio