(Figs. 1A–F)

Male. Body length 4.0–4.5 mm. Wings reaching 8th or 9th abdominal tergite. Dorsal process of 8th tergite situated on high plateau, forming a wide, broadly-arcuate transverse bar directed slightly anterad; tuberculate and noticeably arcuate when viewed dorsally, the concavity directed posteriorly (Figs. 1A–B). Apical segment of epiproct dorsal limb approximately 1.5X length of basal segment, expanded slightly in posterior half in lateral view, with a small subapical indentation (Fig. 1C–D); narrow profile in dorsal view, expanded slightly in posterior third (Fig. 1E).

Female. Body length 5.0–5.5 mm. Wings reaching 9th tergite to beyond tip of abdomen. Eighth abdominal sternite heavily sclerotized medially, gently concave posteriorly with a small medial subtriangular nipple (Fig. 1F); separated from 7th sternite by membrane.

Material examined. Holotype male, U.S.A., Alabama, Jackson Co., spring into unnamed tributary to Big Coon Creek, 4 km NE Hytop, 34° 56.48'N, 086° 03.84'W, 9 II 2008, S. A. Grubbs (SAG) (INHS); Paratypes, same location as holotype but 1 male, 2 female (INHS; WKU); same location as holotype but 6 II 2008, 3 males (WKU); spring into Larkin Fork, Paint Rock River, Rte. 65, 3 km SE Francisco, 19 II 2007, 1 male, 1 female, SAG (WKU).

Etymology. The species name tsalagi is in reference to Cherokee Native Americans, who occupied this region of northeastern Alabama prior to the Indian Removal Act of 1830. The word Tsalagi is Choctaw for “cave-land-people”, an appropriate reference to the well-developed karst landscape in this area. The common name, Tsalagi snowfly, is proposed for this species (Stark et al. 1998).

Diagnosis. Ross & Ricker (1971) defined the A. recta group according to both male and female characteristics. Males lack a dorsal process on the 7th abdominal tergite and possess a single arcuate or incised process that is perched on the 8th abdominal tergite. The 7th and 8th female abdominal sternites are separated by a membrane and the 8th sternite is either unmodified or scarcely modified posteriorly. Using these criteria A. tsalagi can be readily assigned to the A. recta group, which includes A. loshada Ricker, A. malverna Ross, A. mohri Ross & Ricker, A. polemistis Ross & Ricker, A. recta, A. sano Grubbs, A. sequatchie Kondratieff & Kirchner, and A. starki Kondratieff & Kirchner.

The arcuate dorsal process on the 8th abdominal tergite of A. tsalagi (Fig. 1A) is similar only to A. malverna and A. mohri (Figs. 2A–B). The thin, blade-like upper limb of the epiproct of A. mohri (Figs. 2C–D) is distinguished readily from the posteriorly-expanded limbs of A. malverna (Figs. 2E–F) and A. tsalagi (Fig. 1E). Although the upper limb is approximately 1.5X the length of the basal segment for both A. tsalagi and A.

malverna, the upper limb of A. tsalagi (Figs. 1C, 1E) is considerably more elongate than A. malverna in both dorsal and lateral (Figs. 2C–D) aspects. The upper limb of A. malverna is more apically robust and expanded posteriorly, but lacks the subapical indentation that is exhibited by A. tsalagi. In addition, the dorsal process of the 8th abdominal tergite of A. tsalagi is noticeably directed more anteriorly (Fig. 1D) than both A. mohri (Fig. 2C) and A. malverna (Fig. 2E).

The females of both A. malverna and A. mohri typically possess a small, posteromedial projection on the 8th abdominal sternite, a characteristic that is similarly exhibited by A. tsalagi and prevents objective differentiation between the three species. Although A. tsalagi is geographically isolated from both A. malverna and A. mohri, females of A. recta sometimes display a rounded medial projection on the 8th sternite. Allocapnia recta inhabits a wide array of stream sizes and occurs commonly in northeastern Alabama. Allocapnia malverna possesses mainly a Gulf Coastal Plain distribution in Louisiana and Texas with a few scattered localities in Arkansas and Oklahoma, while A. mohri occurs in the Ouachita and Ozark Mountains of Arkansas, Missouri, and Oklahoma (Kondratieff & Baumann 2000; Stark et al. 2008).

Remarks. Allocapnia tsalagi has been collected only from the type locality and the Larkin Fork spring. Both sites are small springs and all material was obtained near their respective sources. The type locality is wetted permanently only for a short distance (<50 m) from the source except during high precipitation events. The sole stonefly species collected with A. tsalagi at the holotype locality was Soyedina cf. vallicularia (Wu). Zealeuctra fraxina Ricker & Ross and S. cf. vallicularia were the only stonefly species obtained with A. tsalagi at the Larkin Fork spring.

The discovery of A. tsalagi is particularly surprising given the recent description of A. sano from a small, calcareous spring in north-central Alabama (Grubbs 2006). The type localities of the two species are separated by only ca. 50 km. Allocapnia tsalagi and A. sano appear to be restricted to springs within the Cumberland Plateau region. Allocapnia tsalagi should be found from additional habitats both in Alabama and north into southern Tennessee.