Nemoura arctica Esben-Petersen 1910

Nemoura arctica Esben-Petersen, 1910

Arctic Forestfly (Figs. 1–52)

http://lsid.speciesfile.org/urn:lsid: Plecoptera.speciesfile.org: TaxonName:6232

Nemoura arctica Esben-Petersen 1910:85.

Holotype ♂, Type locality – Karasjok, Norway

Nemoura trispinosa Claassen 1923:289.

Holotype ♂, Type locality – Mud Creek, Tompkins Co., New York. New synonym (Holotype ♂ examined)

Nemoura trispinosa: Needham & Claassen 1925:213. Nemoura arctica: Claassen 1940:50.

Nemoura trispinosa: Claassen 1940:64.

Nemoura trispinosa: Frison 1942:261

Nemoura arctica: Koponen & Brinck 1949:7.

Nemoura trispinosa: Weber 1950:175.

Nemoura arctica: Brinck 1952:107.

Nemoura trispinosa: Harden & Mickel 1952:19. Nemoura (Nemoura) arctica: Ricker 1952:36.

Nemoura arctica: Zhiltzova 1964:187.

Nemoura arctica: Illies 1966:194.

Nemoura trispinosa: Illies 1966:214.

Nemoura arctica: Lillehammer 1972a:163.

Nemoura trispinosa: Lillehammer 1972a:163.

Nemoura arctica: Zwick 1973a:332.

Nemoura trispinosa: Zwick 1973a:342.

Nemoura arctica: Lillehammer 1974a:82.

Nemoura arctica: Baumann 1975:21.

Nemoura trispinosa: Baumann 1975:21.

Nemoura arctica: Baumann et al. 1977:34.

Nemoura arctica: Lillehammer 1988:113.

Nemoura arctica: Zhiltzova 2003:266.

Nemoura arctica: Kondratieff & Baumann 2004:114. Nemoura arctica: Stewart & Oswood 2006:78.

Nemoura arctica: Judson & Nelson 2012:33.

Distribution. Canada: AB, BC, LB, MB, NB, NS, NT, NU, ON, PE, PQ, YK. Europe: Baltic States, Finland, Norway, Sweden. Mongolia. Russia East, Russia North, West Siberia. USA: AK, IA, IL, ME, MI, NY, OH, PA, SD, WI, WY (DeWalt et al. 2018).

New Canadian province and USA state records.

Canada, Saskatchewan, stream at Promontory Campground, 15 miles north of La Rouge, junction Hwy 102, 21-VI-1976, L.M. Dosdall, 4♂, 2♀; Puskwakau River, Hwy 106, 30-V-1976, L.M. Dosdall, 1♂. USA, Minnesota (Harden & Mickel 1952, their pp. 19–20). New Hampshire, Coös Co., Lakes of the Clouds, White Mountains, 20 June 1951, C.P. Alexander, 1♂ (USNM); Grafton Co., Franconia, A. T. Slosson, no date information, 1♂ (USNM; Ac #26226). West Virginia, Tucker Co., Abe Run, Canaan Valley State Park, 28 May 1993, S.M. Clark, 1♀ (BYU).

Diagnosis.

Cercus. Highly variable. Adults of N. arctica and N. trispinosa have been previously differentiated by a combination of cercal characteristics (males) and body size and distribution (females) (Ricker 1952). Male cerci are sclerotized laterally and terminate typically in a pair of appressed spines that vary in length and degree of tapering (Figs. 1–16), plus a third unit that is highly variable and has been used for the past ca. 65 years to separate males of N. arctica and N. trispinosa (Ricker 1952). Lillehammer (1972a) later illustrated cerci as either lacking (N. arctica, his Fig. 4b) or possessing a distinct (N. trispinosa, his Fig. 4a) spine. Ricker’s (1952, p. 36) key to N. trispinosa males focused on “…the outer edge of the cercus produced into a slender acute spine… may be forked once or twice at the tip”. This feature is common in North America and shown here clearly for populations from Iowa (Fig. 1),

Illinois (Fig. 2), Ohio (Fig. 3), Wisconsin (Fig. 4), South Dakota (Fig. 5), Wyoming (Fig. 6), and New Brunswick (Fig. 8), and also from Siberia (Fig. 12), Norway (Fig. 13) and Mongolia (Fig. 16). The spine, however, varies in width and degree of tapering, For example, males from South Dakota have an outer spine that is rectangular, not “slender”, and crenulated distally (Fig. 5). Nemoura arctica was separated out by Ricker (1952) as the “…outer edge of the cercus bordered by a crenulate shelf or ridge”. No form of a spine is evident for populations studied from North America from Saskatchewan (Fig. 7), Manitoba (Fig. 9), and the Northwest Territories (Figs. 10–11) plus Norway (Fig. 14) and Mongolia (Fig. 15). Overall, there is sufficient variability (e.g. forked vs. crenulated; tapered or not) to strongly suggest that the male cercus does not provide objective, diagnostic information to support N. trispinosa as distinct from N. arctica.

Epiproct. Males exhibit consistency with epiproct shape and characteristics across the Holarctic with only minor differences between individuals. In lateral aspect, the basal cushion occupies the anterior ca. ½ and is separated from the dorsal sclerite by smooth lateral areas (Figs. 17–24). The lateral areas vary in thickness but are consistently recurved slightly over the distal medial portion of the basal cushion. The dorsal sclerite appears scaly at high magnifications, especially at the distal tips (Figs. 41–52). The dorsal sclerite is open apically, exposing parallel, broad, hatchet-like apical prongs of the ventral sclerite (Figs. 25–40) and prominent, scaly, apical prongs positioned ca. perpendicular to the ridges (Figs. 41–52). The prongs terminate laterally bearing two short, thick, grooved spines (e.g. Figs. 42, 45, 49, 52).

Comments. Nemoura trispinosa is placed in synonymy with N. arctica due to consistencies in epiproct characteristics across the Holarctic, particularly the paired apical prongs of the ventral sclerite (Figs. 41–52). In contrast, cercal spine characteristics are highly variable and do not provide objective, diagnostic information. Even males from the same geographic entity (e.g. Mongolia, Figs. 15–16) exhibit different cercal forms. Lillehammer (1972a, his Fig. 25.4) previously illustrated several different cercal forms from Norway.

Geographic notes. Holarctic: Scandinavia east across Asia; east to Alaska, Yukon, Northwest Territories and Nunavut. South in Europe to Latvia and in far eastern Asia to Mongolia and Siberia. South in North America to Wyoming and South Dakota east across the Great Lakes region to Atlantic Canada, with relictual southern populations in Ohio, Pennsylvania, and West Virginia. Additional notable references include Ricker (1944, 1964), Brinck (1958), Ulfstrand (1969), Jewett (1971), Lillehammer (1974, 1985, 1986, 1988), Harper (1973), Flannagan & Flannagan (1982), Burton (1984), Stewart et al. (1990), Harper & Ricker (1994), Stewart & Ricker (1997), Huntsman et al. (1999), Teslenko & Bazova (2009), Walters et al. (2009), Zhou et al. (2010), Boumans (2011), Boumans & Brittain (2012), Surenkhorloo et al. (2012), Dosdall & Giberson (2014), Kendrick & Huryn (2014), and Potikha (2015).