III. Genus Ostrocerca Ricker, 1952

http://lsid.speciesfile.org/urn:lsid: Plecoptera .speciesfile.org:TaxonName:6133

Type species. Nemoura foesteri Ricker, 1943

Range. Nearctic (DeWalt et al. 2022).

Diagnosis. See Baumann (1975) for a comprehensive description of the genus and Young et al. (1989) for an SEM-based treatment for all six Nearctic species.

Species key to eastern Nearctic Ostrocerca adult males and females

1 Males .............................................................................................. 2

- Females............................................................................................. 5

2 Epiproct ventral sclerite apex a singular unit apically and expanded laterally (Figs. 20, 38)........................... 3

- Epiproct ventral sclerite apex sclerite secondarily divided apically into pair dorsal processes and a singular ventral process (Figs. 26‒27, 32‒33)................................................................................... 4

3 Epiproct with a T-shaped ventral sclerite apically (Fig. 21), dorsal sclerite with recurved, paired lateral arms visible in dorsal view (Figs. 20‒22)......................................................................... O. albidipennis

- Epiproct with a bell-shaped ventral sclerite apically (Figs. 37‒38), dorsal sclerite with paired lateral arms not recurved and visible in ventral view (Figs. 39‒40).............................................................. O. truncata

4 Epiproct ventral sclerite terminating in paired processes apically, not recurved and in similar dorsal plane as singular process (Figs. 26‒27)................................................................................ O. complexa

- Epiproct ventral sclerite terminating in paired, dorsally-recurved processes apically, singular process ventrally displaced (Figs. 32‒33).................................................................................... O. prolongata

5 7 th sternum not produced and extended over 8 th sternum, subgenital plate of 8 th sternum with subtriangular lateral projections and medially truncate (Figs. 41‒42)............................................................... O. truncata

- 7 th sternum produced over anterior margin of 8 th sternum as a nipple-like process, subgenital plate of 8 th sternum with gently rounded or subangular lateral corners and medially concave (Figs. 23‒24, 29‒30, 35‒36)............................ 6

6 7 th sternum slightly produced over anterior margin 8 th sternum, subgenital plate of 8 th sternum with gently rounded lateral corners and concave in medial ⅓ (Figs. 23‒24)................................................... O. albidipennis

- 7 th sternum produced at least ¼ of anterior margin 8 th sternum, subgenital plate of 8 th sternum with subangular lateral corners and concave in medial ½ (Figs. 29‒30, 35‒36)..................................... O. complexa and O. prolongata