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).