1.             Maxillae galealacinia with submedian longitudinal row of setae consisting of less than 30 setae. . . 2

                Maxillae galealacinia with submedian longitudinal row of setae consisting of mre than 30 setae. . . 5

2.             Abdominal terga uniformly brown, without pale longitudinal markings or stripes; abdominal sterna                 entirely pale. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stenacron carolina 

                Abdominal terga with pairs of pale stripes or markings submedially and to some extent sublaterally;                 usually some distinct markings on posterior abdominal sterna. . . . . . . . . . . . . . . . . . . . . . . . . .  3

3.             Angulate (left) mandible with inner margin of outer incisor having five to seven denticles. . . . . . . .4

                Angulate terga with inner margin of outer incisor having eight denticles. . . . . . Stenacron candidum

4.             Abdominal terga with submedian longitudinal stripes continuous or nearly continuous; maxillae                 galealacinia with 20-30 setae in submedian row and with 8-10 comblike setae on crown. . . . . . . . . . .                 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stenacron interpunctatum

 5.            Maxillary crowns with 8-10 robust setae in form of distally comblike setae; abdominal sterna with                 dark bands or spots laterally. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stenacron minnetonka

               [Note: the maxillary crown is the distal margin of the main body of the maxilla from the outer                 curvature to the tip.]   

             Maxillary crowns with 11-13 robust setae in form of laterally comblike setae; adominal sterna without                 dark markings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stenacron gildersleevei

Key to Ohio Stenacron Nymph Species

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Mayflies of Ohio
(Modified from McCafferty, et al., 2017 )