Isoperla dewalti Verdone & Kondratieff, 2017

Verdone, Chris J. & Kondratieff, Boris C., 2017, A New Species Of Isoperla Banks (Plecoptera: Perlodidae) From The Southern Appalachians, With Notes On The I. Montana Group, Illiesia 13 (12), pp. 111-126 : 113-120

Isoperla dewalti Verdone & Kondratieff sp. n.

http://lsid.speciesfile.org/urn:lsid: Plecoptera .speciesfile.org: TaxonName:501137

( Figs. 1–20 )

Material examined. Holotype ♂ U.S.A. – Virginia: Grayson Co., Helton Creek, Rte 783 at gated trail by pond , N 36.62816, W 81.56684, 13 May 2017, C. Verdone, B.C. Kondratieff ( INHS, Insect Collection 659585 ) . Paratypes: North Carolina: Avery Co., Shantee Creek, Adams Apple Dr., SW of Foscoe, N 36.12439, W 81.82068, 13 May 2010, B.C. Kondratieff, R.E. Zuellig, D. R. Lenat, R.F. Kirchner, ♂ ( CSUIC). Macon Co., Tellico Creek, Tellico Rd. ~ 0.5 mi. W of Sugar Cove Rd., N 35.27688, W 83.54347, 15 May 2017, C. Verdone, B.C. Kondratieff, ♂ ( CSUIC). Swain Co., Beech Flats Prong, GSMNP, Hwy 441, N 35.60227, W 83.41534, 16 May 2017, C. Verdone, B.C. Kondratieff, ♂ ( CSUIC). Watauga Co., Boone Fork, CR 1561, W of Boone Fork, [N 36.12310, W 81.77006], 2 May 2005, B.C. Kondratieff, R.E. Zuellig, D. R. Lenat, R.F. Kirchner, ♂, 2♀ ( CSUIC). Tennessee: Sevier Co., trib. to Le Conte Creek, GSMNP, Twin Creeks Uplands Research Lab, N 35.68706, W 83.50096, 16 May 2017, C. Verdone, B.C. Kondratieff, 2♂, 2♀ ( CSUIC). Virginia, Franklin Co., Grassy Fork, [Co. Rd. 619, 2 mi. SE Snow Creek Rd.], [N 36.81097, W 79.74516], 21 May 2012, B.C. Kondratieff, R.F. Kirchner, ♂ ( CSUIC). Grayson Co., Same location as holotype, 12 May 2017, C. Verdone, B.C. Kondratieff, J. Richards, R. Agbalog, 4♂, 17♀ ( USNM); Same location as holotype, 13 May 2017, C. Verdone, B.C. Kondratieff, 6♂, 71♀ ( CSUIC); Same location as holotype, 17 May 2017, C. Verdone, B.C. Kondratieff, ♀ ( INHS, Insect Collection 659584).

Distribution. U.S.A. – NC, TN, VA ( Fig. 22 ).

Etymology. The new species is named in honor of Dr. R. Edward DeWalt, Illinois Natural History Survey, Champaign, Illinois, for his dedication and numerous contributions to the study of stoneflies. The proposed common name is the “DeWalt Stripetail”.

Male. Macropterous; forewing length 10.6–11.3 mm (n=5). Body length 9.6–10.0 mm (n=5). Head and pronotum pale yellow with contrasting pigmentation. General body color pale yellow with light brown to brown markings. ( Fig. 1 ). Dorsal background of head pale yellow with medium brown bands connecting ocelli; bands widest anteriorly; bands truncate at anterior ocellus; triangular dusky spot anterior to anterior ocellus ( Fig. 2 ). Antennal scape pale yellow with a diffuse diagonal brown stripe; flagellum segments 1–7 pale; remaining segments medium brown ( Figs. 1–2 ). Pronotum with a wide medial pale stripe; rugosities irregular, raised, medium brown; anterolateral margins medium brown; posterolateral margins pale ( Fig. 2 ). Femora light brown dorsally, covered with uniformly spaced, short, brown setae; femora pale ventrally; tibia light brown, covered with uniformly spaced, short brown setae; tarsi medium brown ( Fig. 1 ). Meso- and metanota light brown ( Fig. 1 ). Wings hyaline, veins of forewing light basally, brown distally ( Fig. 1 ). Terga light brown, posterior ⅓ medium brown; terga 1–8 with uniformly spaced brown setae. Sterna pale yellow to light brown; sternum 8 with a light brown recessed vesicle, 0.65X as wide as long; evenly rounded, extending to the posterior margin of sternum 8 ( Fig. 3 ). Paraprocts short, triangular, slightly incurved, moderately sclerotized; trichoid sensilla scattered over dorsal surface, absent on apex; apex heavily sclerotized; tips acutely pointed ( Fig. 4 ). Cerci brown, setose; cercal segments with a single, long, stout, ventral hair at posterior margin. Aedeagus with a long basal stalk, a highly reduced (vestigial) posteroventral membranous aedeagal tube, a posteroventral lobe, paired posterolateral lobes, a dorsal lobe, and an anterior lobe ( Figs. 5– 10 ); posteroventral membranous aedeagal tube highly reduced (vestigial), appearing only occasionally as a small lobe at the base of the basal stalk ( Fig. 5 ); aedeagus with a posteromedial rectangular patch of dense, stout, rust colored spines, and a single posterior sclerotized arrowhead shaped aedeagal spine plate with upturned distal stout spine ( Figs. 8–10 ); apex of structure upturned with approximately 10 large stout rust colored spines ( Fig. 11 ); base of plate with broad flat sclerotized plates with numerous small apical finger-like projections ( Fig. 11 ); basal stalk with short sharp spinulae ( Fig. 12 ); posterolateral lobes with sparse scale like plates medially; posteromedial area with shallow shelf-like scales with apical hair-like projections ( Fig. 13 ); lateral area with dense short sharp spinulae ( Fig. 14 ).

Female. Macropterous; forewing wing length 11.3– 12.6 mm (n=5). Body length 9.1–10.9 mm (n=5). Body coloration and morphology similar to male. Sternum 8 with variable subgenital plate extending approximately ⅓–½ over sternum 9; subgenital plate broadly rounded ( Fig. 15 ), or broadly triangular, truncate with shallow posteromedian emargination ( Fig. 16 ), or broadly triangular ( Fig. 17 ).

Ovum. Length 226.3–234.4 μm (n=2); width 184.9– 192.5 μm (n=2). General shape oblong; cross section triangular, distinct cross shaped ridges dividing anterior and posterior poles; anterior end concave ( Fig. 18 ). Color pale brown. Collar well-developed, flared apically with elevated longitudinal ridges; base not offset from egg body ( Fig. 19 ). Hexagonal follicle cell impressions well-developed with thickened ridges and with numerous small mounds between reticulations ( Figs. 18, 20 ). Eclosion line absent, micropyles arranged singularly or in threes, positioned on top of cross ridges near anterior ⅓ of egg ( Figs. 18, 20 ).

Larva. Unknown.

Diagnosis. Isoperla dewalti is placed in the I. montana Group based on the presence of a single posterior sclerotized arrowhead shaped aedeagal spine plate with an upturned distal stout spine, dark brown bars connecting the ocelli, and–albeit vestigial–a posteroventral membranous aedeagal tube. The new species is easily distinguished from I. montana and I. nelsoni by the lack of a well-developed posteroventral membranous aedeagal tube.

Several paratype specimens of I. dewalti that are deposited in the C. P. Gillette Museum of Arthropod Diversity had previously been identified as I. montana . The two species are superficially similar and it was likely thought that the posteroventral membranous aedeagal tube did not evert. However, it is the experience of the authors that when a welldeveloped aedeagal tube is present it is the first structure to evert. Additionally, differences in the posteromedial patch of spines distinguish the two species. In I. dewalti the posteromedial patch of spines is broad, appearing as a uniform rectangular patch ( Figs. 8–10 ). Whereas, in I. montana the posteromedial patch of spines is narrow, appearing as a thin ridge (figs. 33.15–33.16, Szczytko & Kondratieff 2015). Furthermore, I. montana possesses a dorsal rounded mound of dense, long, stout, rust colored spines above the posteromedial patch of spines (figs. 33.15–33.16, Szczytko & Kondratieff 2015), which the new species lacks.

Females of the new species are most similar to I. montana and I. kirchneri Szczytko & Kondratieff, 2015 . Females of the new species have a subgenital plate that extends approximately ⅓–½ over sternum 9 and appears broadly rounded ( Fig. 15 ), or broadly triangular, truncate with shallow posteromedian emargination ( Fig. 16 ), or broadly triangular ( Fig. 17 ), and have a dorsal head pattern with brown bands connecting the ocelli that are truncate at the anterior ocellus with a triangular dusky spot anterior to the anterior ocellus ( Fig. 2 ). Females of I. montana and I. kirchneri also have a subgenital plate that is variable, appearing broadly triangular usually with a shallow posteromedian emargination or pointed (figs. 25.5, 33.7, Szczytko & Kondratieff 2015) and have dorsal head patterns with brown bands connecting the ocelli. In I. montana the bands extend anteriorly to near the frons (occasionally pale brown or faint), and without a medium brown anterior patch near the frons (fig. 33.1, Szczytko & Kondratieff 2015). In I. kirchneri the bands sometimes extend anteriorly from the anterior ocellus, with a well-defined to diffuse spot on frons (fig. 25.1, Szczytko & Kondratieff 2015). The variation in subgenital plate morphology and dorsal head pattern exhibited by these species make the separation of isolated females very difficult.

Ova of the new species are similar to I. kirchneri , I. montana , I. nelsoni , and I. signata (Banks, 1902) , all of which are oblong and triangular in cross section with distinct cross shaped ridges dividing anterior and posterior poles. Ova of the new species are distinguished from other similar ova by the interreticulate follicle cell impressions, which are developed as mounds in the new species ( Figs. 18, 20 ) and punctations in the other similar species (figs. 25.19–25.22, 33.25–33.28, 36.9–36.11, 50.20–50.23, Szczytko & Kondratieff 2015).

Biological notes. There is no information about the biology or life cycle of I. dewalti . Based on the above records, the emergence period appears to be in early to mid-May, and as with most eastern Isoperla , a univoltine life cycle is presumed. The type locality, Helton Creek, has a unique stonefly fauna, species with generally northern distributions (e.g. Alloperla concolor Ricker, 1936 ) and species with generally southern distributions (e.g. Haploperla parkeri Kirchner & Kondratieff, 2005 ) have been documented from this location. From the limited records available it is inferred that the new species also has a generally southern distribution, occurring in 1 st –3 rd order streams in the Piedmont Plateau and the southern Blue Ridge physiographic provinces ( Fig. 22 ).

Figures

Fig. 1. Adult habitus of Isoperla dewalti sp. n., Helton Creek Grayson Co., Virginia, 2X.

Figs. 2–4. Isoperla dewalti sp. n., Helton Creek, Grayson Co., Virginia, 5X. Fig. 2. Head and pronotum, dorsal. Fig. 3. Male sterna 7–9, ventral. Fig. 4. Male paraprocts, dorsal.

Figs. 5–7. Aedeagus of Isoperla dewalti sp. n., lateral, 5x. A. (vestigial) posteroventral membranous aedeagal tube, B. Posteroventral lobe, C. Posterior sclerotized arrowhead shaped aedeagal spine plate with upturned distal stout spine, D. Paired posterolateral lobes, E. Posteromedial rectangular patch of dense, stout, rust colored spines, F. Dorsal lobe, G. Dense short sharp spinulae, H. Anterior lobe. Fig. 5. Helton Creek, Grayson Co., Virginia. Fig. 6. Tributary to Le Conte Creek, Sevier Co., Tennessee. Fig. 7. Helton Creek, Grayson Co., Virginia.

Figs. 8–10. Aedeagus of Isoperla dewalti sp. n., posterior, 5x. B. Posteroventral lobe, C. Posterior sclerotized arrowhead shaped aedeagal spine plate with upturned distal stout spine, D. Paired posterolateral lobes, E. Posteromedial rectangular patch of dense, stout, rust colored spines, F. Dorsal lobe, G. Dense short sharp spinulae, Fig. 8. Helton Creek, Grayson Co., Virginia. Fig. 9. Tributary to Le Conte Creek, Sevier Co., Tennessee. Fig. 10. Helton Creek, Grayson Co., Virginia.

Figs. 11–14. Isoperla dewalti sp. n., Helton Creek, Grayson Co., Virginia. Fig. 11. Posterior sclerotized arrowhead shaped aedeagal spine plate with upturned distal stout spine and broad flat sclerotized plates with numerous small apical finger-like projections, 1,800X. Fig. 12. Short sharp spinulae, 700X. Fig. 13. Shelflike scales with apical hair-like projections, 1,200X. Fig. 14. Aedeagus, lateral, lateral area with dense short sharp spinulae (arrow) 65X.

Figs. 15–17. Female subgenital plate of Isoperla dewalti sp. n., Helton Creek, Grayson Co., Virginia, 5X. Fig. 15. Broadly rounded Fig. 16. Broadly triangular, truncate with shallow posteromedian emargination. Fig. 17. Broadly triangular.

Figs. 18–20. Isoperla dewalti sp. n., Tributary to Le Conte Creek, Sevier Co., Tennessee. Fig. 18. Ovum, 400X. Fig. 19. Ovum collar, 1,800X. Fig. 20. Ovum follicle cell impressions and micropyles, 800X.

Fig. 22. Distribution map of examined material and physiographic provinces.