Perlesta ephelida, a new Nearctic stonefly species (Plecoptera, Perlidae)

Abstract A new Nearctic species of Perlidae (Insecta, Plecoptera), Perlesta ephelida sp. n., is described from the male, female, and egg stages. This species has been previously reported as, or confused with, Perlesta shubuta Stark from several central and eastern U.S. states. Perlesta ephelida is distinctive from Perlesta shubuta and other regional Nearctic congeners mainly according to male genitalic and egg characteristics. Perlesta ephelida is a widely-distributed eastern Nearctic species, whereas Perlesta shubuta appears to be restricted to a narrow latitudinal belt in the Gulf Coast region from Louisiana east conservatively to the Florida panhandle. The egg of Perlesta shubuta is depicted with scanning electron microscopy for the first time.

The male aedeagus of P. shubuta bears a thumb-shaped caecum, a common feature for the genus (Stark 2004) and part of the reason why this species is somewhat difficult to identify with complete certainty. The female subgenital plate is likewise similar to other species. Although the morphology of the egg appears to be distinctive (Stark 1989) it has yet to be studied with scanning electron microscopy to reveal fine structural details of the chorion.
The type locality for P. shubuta is a sandy-bottom headwater stream. Poulton and Stewart (1991), DeWalt et al. (2001), and Heimdal et al. (2004), however, reported P. shubuta from large stream systems. DeWalt and Grubbs (2011) suggested that the Illinois and Indiana specimens they tentatively determined as P. shubuta may represent a new species. Stark (1989) and Poulton and Stewart (1991) both commented on "extremely freckled" and "speckled" nymphs, respectively, from the Ozark and Ouachita Mountain region, and the latter authors stated that "…our specimens are tentatively placed under P. shubuta and may represent an undescribed species".
Our material that we only tentatively identified as P. shubuta from throughout the central and eastern U.S. has been obtained mainly from larger systems, including low elevation Appalachian Mountain rivers in Alabama, Maryland and West Virginia, and sandy-bottom lowland rivers in Illinois, Indiana and Michigan. Associated nymphs and exuviae obtained through rearings bear a head mask that is freckled to a much greater degree compared to regional congeners. Because of the uncertainty regarding the identity of P. shubuta from localities other than at/near the type locality in southern Mississippi, a comparative study was undertaken to examine available material from across the central and eastern U.S.

Materials and methods
Fresh specimens of P. shubuta were obtained from eastern Mississippi and western Alabama in May 2011. A visit to the type locality was unsuccessful. Recently collected material of P. shubuta, in addition to all specimens determined tentatively as P. shubuta, was reexamined with light microscopy to study fine details of the paraprocts, dorsal and lateral aedeagal spinule patterns, and the subgenital plate. Material were obtained from collections from the Bill P. Stark Creek, Alvaton, 36.8704, -86.3683, 2.vi.1999, S.A. Grubbs (INHS).
Adult habitus. Head yellow with a dark brown subquadrate ocellar patch and a small, light brown subtriangular patch anterior to the anterior ocellus, pronotum golden-brown with a very faint lighter medial stripe in some specimens (Fig. 1). Wing membrane and veins amber except for pale costal region. Femora dorsally brown, laterally and ventrally yellow; tibia brown. Abdominal terga and sterna yellow. Cerci pale yellow proximally, brown distally.
Nymph. Undescribed. Etymology. The species name is a derivation of the Greek word ("ephelis") for freckle (Brown 1956), in reference to the heavily-freckled head mask of the nymphs and associated exuviae.
Diagnosis. The males of P. ephelida will key to couplets 11 and 12 in Stark (2004), with a paraproct spine visible in lateral view and a group that includes P. shubuta Stark, P. puttmanni Kirchner, 2003, andP. decipiens (Walsh, 1862). Although the paraproct spine of P. ephelida is directly somewhat anteriorly, it is mainly mesally-directed and typically seen in dorsal aspect , and superficially similar to P. puttmanni (see Kondratieff and Kirchner 2003, Fig. 10). The paraproct spine of P. shubuta is not visible in dorsal aspect and the tips are rounded apically (Fig. 8); the epiproct tips are pointed apically in P. ephelida (Figs 9-13). The paraproct spine in P. puttmanni is visible caudally (see Kondratieff and Kirchner 2003, Fig. 12), which is also seen in this aspect in P. ephelida (Fig. 3), but is not visible in P. shubuta (see Stark 2004, Fig. 7.352). The narrow aedeagal dorsal patch of P. ephelida (Fig. 4) is slightly broader than P. puttmanni (see Stark 2004, Fig. 7.367), whereas both P. shubuta (see Stark 2004, Fig. 7.369) and P. decipiens (see Stark 2004, Fig. 7.306) bear conspicuously broader patches. The egg of P. ephelida possesses a wide, well-developed, and distally-flanged collar (Figs 15,17,19,21), resembling P. decipiens (Stark 2004, Fig. 7.397) but easily contrasted from the short collars of P. shubuta (Figs 23-24), and P. puttmanni (see Kondratieff and Kirchner 2003, Fig. 15). The subgenital plate of P. decipiens (see Stark 2004, Fig. 7.379) has prominent truncate lobes and a deep v-shaped notch while the medial notch of P. ephelida is shallow and v-shaped (Fig. 7). The female of P. ephelida can only be confidently identified if mature eggs are present and associated with a male with a fully-extruded aedeagus.
Perlesta ephelida is distributed broadly across the central and eastern U.S. from eastern Alabama northeast to Massachusetts, north to the Great Lakes region and Iowa, and northwest to the Interior Highlands region of Arkansas, Missouri, and Oklahoma. Perlesta ephelida is expected to be collected from intervening states (e.g. Pennsylvania, Tennessee) where this species has yet to be reported. In contrast, P. shubuta appears to be restricted to a narrow latitudinal belt in the Gulf Coast region of the southeastern U.S., known currently from Louisiana east to northern Florida panhandle and likely to South Carolina.
The Modified key to couplets 11 and 12 in Stark (2004) to identify males of Perlesta ephelida: