Three-lobed Needlefly

http://lsid.speciesfile.org/urn:lsid: Plecoptera.specie sfile.org:TaxonName:462470

(Figs. 34‒42)

Leuctra triloba Claassen 1923:258. Holotype ♂ (CUIC), McLean, New York

Leuctra triloba: Needham and Claassen 1925:233

Leuctra crosbyi: Claassen 1937:45. Syn. Illies 1966

Leuctra triloba: Illies 1966:110

Leuctra triloba: Zwick 1973:408

Male. The 7th abdominal dorsal process bears three lobes, with the medial lobe terminating more posteriorly than the paired lateral lobes (Figs. 34‒ 36). The specilla are very broad basally, scarcely recurved anteriorly (Figs. 39, 41), and bear raised tubercles distally along outer margins (Figs. 37‒38, 40, 42). The subanal lobes are narrow throughout length, tapering and recurved anteriorly, and ca. 80% the length of the specilla (Figs. 39, 41).

Material examined. USA, Alabama, Clay Co., tributary to West Fork Hatchet Creek, Talladega National Forest, 33.2912, -86.0723, 25 January 2006, A.L. Sheldon, 3♂, 2♀ (WKUC); Mill Shoals Creek, Talladega National Forest, 33.4201, -85.8070, 6 November 2011, A.L. Sheldon, 1♂ (WKUC); Cleburne Co., Dry Creek, 33.8725, -85.5811, 7 November 2011, A.L. Sheldon, 1♂, 5♀ (WKUC). North Carolina, Burke Co., Linville River, above Linville Falls, 27 November 2002, 35.9541, -81.9279, S.A. Grubbs, 1♂, 3♀ (WKUC); Haywood Co., Cold Springs Creek, Pisgah National Forest, 35.7785, - 82.9559, 2 March 2008, S.A. Grubbs, 1♂, 1♀ (WKUC); tributary to Yellowstone Prong, 35.3219, - 82.8518, 24 October 2014, A.L. Sheldon, 3♂, 3♀ (WKUC); Macon Co., Wine Spring Creek, Nantahala National Forest, 35.1761, -83.5897, 1 October 2013, A.L. Sheldon, 6♂, 10♀ (WKUC); Sassafras Branch, Nantahala National Forest, 35.1895, -83.5939, 20 November 2013, A.L. Sheldon, 3♂, 7♀ (WKUC). Tennessee, Marion Co., tributary to South Suck Creek, Prentice Cooper State Forest, 35.1597, -85.4065, 12 February 2007, S.A. Grubbs, 1♂, 2♀ (WKUC); same locality but 31 January 2015, S.A. Grubbs, 1♂ (WKUC); tributary to South Suck Creek, Prentice Cooper State Forest, 35.1474, - 85.3926, 12 February 2007, S.A. Grubbs, 1♂, 1♀ (WKUC).

Distribution. Canada: PQ. USA: AL, FL, NC, NY, SC, VA, WV (DeWalt et al. 2015), TN (new state record).

Remarks. This species exhibits variability in the dorsal abdominal process, namely the size of the lateral lobes compared to the medial lobe (Hitchcock 1974, fig. 86). The dorsal processes depicted herein from Alabama (Fig. 34) and North Carolina (Fig. 35) are very similar to one form shown in Hitchcock (1974, fig. 86c). The Alabama and North Carolina populations are also very similar to the dorsal process in Claassen (1923, fig. 19) of the holotype male from New York. The males from Tennessee, however, bear a dorsal process that is different (Fig. 36) from specimens from Alabama and North Carolina, and similar to Hitchcock (1974, fig. 86b). The lateral lobes are smaller and can appear near-absent even under a dissecting microscope. Paraproct characteristics from the Alabama and North Carolina material were identical to the Tennessee males.

This species has a narrow and long north-south distribution from Quebec to Florida (DeWalt et al. 2015). The sporadic nature of its known distribution is likely due to an adult emergence pattern that is mainly autumnal, a period with very low adult stonefly diversity and less frequented collecting efforts. This is the only species in the L tenuis group with an emergence period that extends through winter..