Ostrocerca truncata ( Claassen, 1923 )

Grubbs, Scott A. & Baumann, Richard W., 2023, The Nemourinae (Insecta, Nemouridae) of the eastern Nearctic, Zootaxa 5306 (1), pp. 1-53 : 15

5. Ostrocerca truncata ( Claassen, 1923)

Truncate Forestfly

http://lsid.speciesfile.org/urn:lsid: Plecoptera .speciesfile.org:TaxonName:6135

( Figs. 37–42 )

Nemoura truncata Claassen, 1923 . Holotype male ( Museum of Comparative Zoology ), Walden, (Middlesex Co.), Massachusetts, USA

Nemoura truncata: Needham & Claassen, 1925:218

Nemoura truncata: Claassen, 1940:64

Nemoura (Ostrocerca) truncata: Ricker, 1952:40

Nemoura (Ostrocerca) albidipennis: Ricker, 1965:490

Ostrocerca truncata: Illies, 1966:218

Nemoura (Ostrocerca) truncata: Harper & Hynes, 1971:1136

Ostrocerca truncata: Zwick, 1973:344

Nemoura (Ostrocerca) truncata: Hitchcock, 1974:109

Ostrocerca truncata: Baumann, 1975:53 , 66 (in part)

Ostrocerca truncata: Stewart & Stark, 1988:173

Ostrocerca truncata: Young et al., 1989:263

Ostrocerca truncata: Stewart & Stark, 2002:200

Ostrocerca truncata: Stark, 2017:212

Distribution. Canada: ON, PQ. USA: AL, CT, IN, KY, MA, MD, ME, NY, OH, PA, VA, WV ( DeWalt et al. 2022)

New state records. IL: Union Co., tributary Wolf Lake , Pine Hills CG, Shawnee National Forest , 37.51724 -89.42172, 20 April 2022, 1 male, R. E. DeWalt, L. Hart ( INHS) . TN: Anderson Co., tributary to New River , 11 km NW Oliver Springs, 36.1246, -84.4168, 26 March 2004, 2 males, S.A. Grubbs ( WKUC); Marion Co. , tributary to South Suck Creek, 11 km ESE Whitwell, 35.1597, -85.4065, 29 May 2003, 1 female, S.A. Grubbs ( WKUC) .

Male. Macropterous. Body length 4.2–5.4 mm, forewing length 5.5–6.4 mm (n = 17). Gills absent. Cerci enlarged but compact, sclerotized, and curving medially to an apical point ( Figs. 37–38 ). Paraprocts divided into a membranous outer lobe and a sclerotized, sickle-shaped inner lobe; inner lobes short, tapering along a smooth curve and divergent apically ( Fig. 40 ; Young et al. 1989, their fig. 25). Epiproct elongate and complex; dorsal sclerite smooth with a middorsal groove and ventrally with small posteriorly-projected lateral arms ( Fig. 40 ); ventral sclerite with basal, mid-dorsal groove and apically laterally expanded and bell-shaped ( Figs. 37–39 ).

Female. Macropterous. Body length 4.3–6.6 mm, forewing length 6.3–7.5 mm (n = 17). Gills absent. Cerci enlarged but unmodified ( Fig. 41 ). The 8 th sternum is enlarged as a subgenital plate and extended over the anterior margin of the 9 th sternum. The plate is broad basally, narrowing slightly such that the posterior half is approximately 3/4 of the sternum width; posterolateral corners of the plate are extended as subtriangular processes and the medial region is either straight or with a small gently-rounded medial projection ( Figs. 41–42 ). The 7 th sternum is unmodified ( Figs. 41–42 ).

Larva. Stewart & Stark (2002) provided a full habitus illustration. Partial illustrations were also given by Baumann (1975), Harper & Stewart (1996), and Stark (2017)

Comments. Similar to the other three eastern Ostrocerca species, O. truncata exhibits a widespread Appalachian distribution ( DeWalt et al. 2022) but extends further southward through Tennessee to northeastern Alabama ( Young et al. 1989) and westward across southern Ohio ( DeWalt et al. 2016) to southern Indiana ( Grubbs 2004), southern Illinois, and central Kentucky ( Grubbs et al. 2005).

Figures

FIGURES 37‒42. Ostrocerca truncata. 37, male abdominal terminalia, dorsal view; 38, Canada, Ontario, Clare River, male abdominal terminalia, dorsal view; 39, Canada, Ontario, Clare River, epiproct, lateral view; 40, male abdominal terminalia, ventral view; 41, USA, New York, Cascadilla Creek, female abdominal terminalia, ventral view; 42, USA, West Virginia, headwaters Davis Creek, female abdominal terminalia, ventral view. c = cercus, ds = dorsal sclerite, hy = hypoproct, ipl = inner paraproct lobe, la = lateral arm, sgp = subgenital plate, vs = ventral sclerite.