Leuctra schusteri sp. n.

http://lsid.speciesfile.org/urn:lsid: Plecoptera .specie sfile.org:TaxonName:472643

(Figs. 10‒18)

Male. Forewing length 4.5–5.5 mm, body length 4.5–6.0 mm (n=15). General body color and wings brown. Cerci tubular and unmodified. Abdominal terga 1–6 unmodified. Dorsal process on abdominal tergum 7 emanating from anterior margin of segment, tapering markedly to the posterior tip that is slightly bulbous and expanded medially, overall shape of process triangular (Figs. 10‒11). Abdominal tergum 8 unmodified except for a quadrate-shaped lightly-pigmented medial sclerite. Epiproct sclerite unmodified and narrow throughout length, tapering slightly posteriorly. Specilla broadest basally, tapering little throughout length (Figs. 14‒15), generally lacking tubercles along distal outer margins (Figs. 12‒15), tip bears a conspicuous, laterally-directed spur (Figs. 12‒13). Subanal lobes flat, slightly recurved anteriorly, and subequal in length to specilla (Figs. 14‒15). Vesicle small and subtriangular, length ca. equal to width at base (Fig. 18).

Female. Forewing length 5.5–7.0 mm, body length 5.5–7.5 mm (n=21). General body color similar to male. Abdominal sternum 7 with a pentagonalshaped medial sclerite. Abdominal sternum 8 sclerotized medially in anterior ½; subgenital plate lobes rounded posterolaterally and angular along the mediolateral corners; lobes separated by a membranous diamond-shaped medial notch, extending maximally over the anterior ¼ of abdominal sternum 9 (Figs. 16‒17).

Larva. Undescribed.

Material examined. Holotype ♂, USA, Kentucky, Hart Co., Cooper Spring, 37.1974, -86.0476, Mammoth Cave National Park, 15 September 2015, S.A. Grubbs (USNM) . Paratypes: Kentucky, Allen Co., spring into Smyrna Creek, 6.5 km SE Gold City, 36.6777, -86.3913, 8 October 2013, S.A. Grubbs, 17♂, 43♀ (INHS, USNM, WKUC) . Adair Co., Spout Spring Branch, 24 km SE Campbellsville, 37.2020, -85.1480, 3 October 2013, S.A. Grubbs, 1♂, 3♀ (WKUC) ; tributary to Sulphur Creek, 10 km NE Columbia, 37.1346, -85.1946, 3 October 2013, S.A. Grubbs, 1♂, 13♀ (WKUC) . Edmonson Co., springhead in Fish Trap Hollow, Sal Hollow Trail, 37.1983, -86.1443, Mammoth Cave National Park, 15 September 2015, S.A. Grubbs, 1♂, 9♀ (WKUC) ; spring run into Ugly Creek, 37.2393, - 86.1476, Mammoth Cave National Park, 15 September 2015, S.A. Grubbs, 5♂, 10♀ (WKUC) ; spring run into Ugly Creek, 37.2374, -86.1092, Mammoth Cave National Park, 15 September 2015, S.A. Grubbs, 8♂, 9♀ (WKUC) ; Good Church Spring, 37.2096, -86.1476, Mammoth Cave National Park, 17 September 2015, S.A. Grubbs, 2♂, 5♀ (WKUC) ; spring out of Silent Grove Springhouse Cave, 37.1716, -86.1836, Mammoth Cave National Park, 24 September 2015, S.A. Grubbs, 1♂, 2♀ (WKUC) ; Blue Spring, Mammoth Cave National Park, 37.2424, -86.1797, 5 October 2015, S.A. Grubbs, 3♂, 3♀ (WKUC) ; Sand Spring, Mammoth Cave National Park, 37.2340, -86.1547, 11 October 2015, S.A. Grubbs, 1♂ (WKUC) ; tributary to Wet Prong Buffalo Creek, Mammoth Cave National Park, 37.2404, -86.1738, 11 October 2015, S.A. Grubbs, 1♂, 1♀ (WKUC) . Green Co., spring into Big Brush Creek, nr. Rte. 569, 9 km WNW Summersville, 37.3441, -85.6236, 1 October 2013, S.A. Grubbs, 2♂, 3♀ (WKUC) ; Hart Co., spring into Roundstone Creek, 7.5 km NW Bonnieville, 37.4105, -85.9823, 17 July 2001, S.A. Grubbs and J.M Taylor, 1♂, 3 nymphs (WKUC) ; same but 7–28 September 2002, S.A Grubbs, 5♂, 6♀ (WKUC); same but 26 September 2003, S.A Grubbs, 7♂, 6♀ (WKUC); spring into Lynn Camp Creek, nr. Rte. 569, 14 km NW Summersville, 37.3545, -85.7128, 1 October 2013, S.A. Grubbs, 1♂, 13♀ (WKUC) ; same as holotype, 4♂, 10♀ (WKUC); Collins Spring, 37.2061, -86.0489, Mammoth Cave National Park, 15 September 2015, S.A. Grubbs, 1♂, 4♀ (WKUC) ; Warren Co., tributary to Shanty Hollow Lake, 8.5 km NE Richardsville, 37.1390, -86.3849, 4 October 2013, S.A. Grubbs, 1♂, 4♀ (WKUC) .

Etymology. This species is named in honor of Dr. Guenter Schuster, Foundation Professor of Biological Sciences, Eastern Kentucky University. Dr. Schuster and his students have spent many years studying the aquatic fauna of Kentucky.

Diagnosis. The combination of the well-defined dorsal process on the 7 th abdominal tergum and a small triangular vesicle places L. schusteri sp. n. in the L. tenuis species group (Harper & Harper 1997). The posteriorly tapering process on the 7 th abdominal tergum of L. schusteri sp. n. (Figs. 10‒11) is similar only to L. tenuis (Figs. 23‒25), and very distinct from L. carolinensis (Figs. 1‒3), L. tenella (Fig. 19), L. triloba (Figs. 34‒36), L. usdi (Fig. 43), and L. variabilis (Fig. 48).

Leuctra schusteri sp. n. can be distinguished from L. tenuis by paraproct characteristics. The subanal lobes of L. schusteri sp. n. are approximately the same length as the specilla (Figs. 14‒15) whereas with L. tenuis the subanal lobes extend ca. ¾ the length of the specilla (Figs. 28‒30, 32). The specilla of L. schusteri sp. n. possess a prominent, laterallydirected spur (Figs. 12‒12). In contrast, the specilla of L. tenuis is rounded distally and lack a spur (Figs. 27, 31, 33). The dorsal process on the 7 th abdominal tergum of L. schusteri sp. n. (Figs. 10‒11) and L. tenuis (Figs. 23‒25) are too similar in overall appearance, namely shape and size, to provide reliable diagnostic value.

As is the case for most Nearctic Leuctra, possessing females definitively associated with males is the easiest means of differentiating between species. Females of L. schusteri sp. n. and L. tenuis are very similar morphologically, particularly in the shape of the subgenital plate lobes and pigmentation patterns in darker individuals. Both species have lateral indentations that essentially demarcate the anterior plane of the lobes.

Remarks. The type locality is a small spring run that emanates from a limestone bluff in southcentral Kentucky (Figs. 53‒54). Most adults were collected proximal to the spring source. All paratype localities are also springheads or small spring runs. No other species of stoneflies were collected in the adult stage.

The type and all paratype localities (Fig. 53) are located within the Interior Plateau Level III Ecoregion, a region characterized by Mississippianage limestone, extensive karst development, and emergent spring systems (Woods et al. 2002). The range of this species likely extends southward into Tennessee since one paratype locality (Allen Co., spring into Smyrna Creek) is only ca. 3 km north of the state border. Northward into unglaciated southern Indiana and southern Ohio, L. tenuis has been the only autumn-emergent Leuctra collected. Similarly, only L. tenuis has been collected eastward into the Appalachian Plateau region of eastern Kentucky and West Virginia.

Grubbs et al. (2006) showed that L. schusteri sp. n. (as L. cf. tenuis) exhibited a univoltine-slow life cycle. Nymphs were present by early January and appear to require continuous flow in the spring run during the dry summer months. Leuctra nymphs present through summer were presumably only L. schusteri sp. n. since this was the only adult species collected from July through early October. The common name, Karst Needlefly, is proposed for this species (Stark et al. 2012).