1. Paraprocts sclerotized, recurved over abdominal apex; hammer present on sternum 9; sternum 8 unmodified . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Males, 2
Paraprocts membranous and poorly developoped; hammer absent; sternum 8 with a subgenital plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Females, 11
2. Paraprocts broad, at least basally; apical aedeagal patch absent. . . . . . . . . . . . . . . . . . . 3
Paraprocts slender, finger-like for entire length; apical aedeagal patch present . . . . . . . . . 5
3. Paraprocts triangular in outline; apical aedeagal section shorter than basa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acroneuria abnormis
Paraprocts broad at base, slender apically; apical aedeagal section longer than basal . . . . 4
4. Basal aedeagal patac notched basally, continuous dorosapically . . . . . . . . A. carolinensis
Basal aedeagal patch completely divided by narrow membranous band. . . . . . . A. lycorias
5. Ventral aedeagal patch without narrow stalk of setal-like spines . . . . . . . . . . . . . . . . . . . 6
Ventral aedeagal patch with narrow mesal stalk of dark setal-like spines . . . . . . . . . . . . . 8
6. Basal aedeagal patch extends over ventral, basally directed lobe . . . . . . . . . . A. internata
Ventral, basally directed lobe, if present not covered by basal patch . . . . . . . . . . . . . . . . 7
7. Basal membranous lobe of aedeagus directed toward apex and bearing a sparse patch of setae; dorsoapical lobe of aedeagus broadly covered by apical patch . . . . . . . . . . . . A. covelli
Basical membranous lobe without setal patch; dorsoapical aedeagal lobe with apical patch more or less V-shaped . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. frisoni
8. Apical aedeagal patch shevron, or chordate-shaped . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Apical aedeagal patch quadrangular, or a pair of narrowly separated patches. . . . . . . . . 10
9. Basal aedeagal patach undivided; ventral stalk long . . . . . . . . . . . . . . . . . . A. kosztarabi
Basal aedeagal patch divided; ventral stalk short . . . . . . . . . . . . . . . . . . . . . . . . A. filicis
10. Stalk of ventral aedeagal patch very narrow; apical aedeagal patch usually united by narrow mesal zone of fine setal-like spines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. perplexa
Stalk of ventral aedeagal patch wide; apical aedeagal patch completely divided by membrane; ocellar area usually dark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. evoluta
11. Females. Most of chorionic surface coarsely pitted, strawberry-like . . . . . . . . . . . . . . 12
Chorionic surface pitting restricted to apex, or absent, or surface covered with hexagonal follicle cell impressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
12. Chorionic surface smooth around collar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. covelli
Chorionic surface completely pitted . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A. kosztarabi
13. Apex of egg deeply pitted . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Apex of egg smooth, or with obscure follicle cell impressions . . . . . . . . . . . . . . . . . . . . 16
14. Subgenital plate bilobed, posterolateral angles curled ventrally . . . . . . . . . . A. internata
Subgenital plate entire, emarginated or notched, posterolateral angles not curled. . . . . 15
15. Egg collar small, indistinct; forewing length less than 28 mm . . . . . . . . . . . . A. perplexa
Egg collar wide, distinct; forewing length 28-31 mm. . . . . . . . . . . . . . . . . . . . . A. filicis
16. Egg collar absent; forewing length 16-21 mm . . . . . . . . . . . . . . . . . . . . . . . . . A. frisoni
Egg collar button-like; forewing length 21-33 mm. . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
17. Subgenital plate well developed, covering 1/3 to ½ of sternum 9; egg pear-shaped . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. evoluta
Subgenital plate poorly developed, covering less than 1/3 of sternum 9; egg oval. . . . . . 18
18. Subgenital plate essentially undeveloped . . . . . . . . . . . . . . . . . . . . . . . . . A. abnormis
Subgenital plate poorly to moderately developed . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
19. Subgenital plate with a triangular notch . . . . . . . . . . . . . . . . . . . . . . . . . A. carolinensis
Subgenital plate without triangular notch . . . . . . . . . . . . . . . . . . . . . . . . . . . A. lycorias
Key to the Adult Acroneuria of Ohio