Isoperla davisi James, 1974

Verdone, Chris J., Beaty, Steven R., Holland, Victor B. & Williams, Bronwyn W., 2023, Isoperla riverae, a new stonefly species from the southeast Nearctic, with notes on sympatric species including the larval description of Isoperla lenati Szczytko & Kondratieff, 2015 (Plecoptera: Perlodidae), Zootaxa 5270 (3), pp. 437-470 : 439-446

Isoperla davisi James, 1974

( Figs. 10–14 )

Alabama Stripetail

http//lsid.speciesfile.org/urn:lsid: Plecoptera .speciesfile.org:TaxonName:468717

Isoperla davisi James 1974:996 . Holotype male (INHS), Saugahatchee Creek , Tallapoosa Co., Alabama, U.S.A.

Isoperla coushatta Szczytko & Stewart 1976:211 . Holotype male (INHS), Saddler Creek, Anderson Co., Texas, U.S.A. Syn. Szczytko & Kondratieff, 2015:73.

Isoperla coushatta: Szczytko & Stewart 1977:358 .

Isoperla coushatta: Poulton & Stewart 1991:47 .

Isoperla davisi: Szczytko & Kondratieff 2015:73 .

Distribution. USA: AL, AR, DE, FL, LA, MO, MS, NC, OK, SC, TX, VA. ( DeWalt et al. 2023)

Material examined. U.S.A. — North Carolina: Alamance Co., Haw River, NC 87, 36.18250, -79.50944, 2 May 1985, T. MacPherson, 4L ( NCDWR). Bladen Co., Browns Creek, NC 87, 34.61339, -78.58489, 7 February 2008, S. Beaty, M. Walters, 6L ( NCDWR). Cleveland Co., Lick Branch, SR 2227, 35.17694, -81.50111, 17 March 1986, D. Penrose, 15L ( NCDWR). Edgecombe Co., Whiteoak Swamp, SR 1428, 36.00444, -77.62028, 3 May 1988, T. MacPherson, 1M, 13L ( NCDWR); Whiteoak Swamp, NC 43, 36.00444, -77.62028, 5 February 2007, B. Crouch, B. Prusha, M. Walters, 9L ( NCDWR). Gaston Co., Beaverdam Creek, SR 1609, 35.40444, -81.24528, 5 May 2006, B. Prusha, M. Walters, 9L ( NCDWR). Guilford Co., Hickory Creek, SR 1132, 35.94027, -79.86888, 16 April 2003, K. Herring, B. Crouch, 10L ( NCDWR). Iredell Co., Patterson Creek, SR 1890, 35.92417, -80.82417, 4 April 2006, E. Fleek, T. MacPherson, 14L ( NCDWR). Moore Co., UT McLendons Creek, SR 1261, 35.34964, -79.47894, 28 March 2019, emerged 11 April 2019, S. Beaty, C. Verdone, V. Holland, L. Housley, 1M, 1E ( NCDWR). Moore/ Richmond Co., Drowning Creek, SR 1102, 35.08426, -79.58270, 28 March 2019, emerged 8 April 2019, S. Beaty, C. Verdone, V. Holland, L. Housley, 1M, 1E ( NCDWR); same location, 28 March 2019, S. Beaty, C. Verdone, V. Holland, L. Housley, 1M, 1E ( NCDWR); same location, 17 April 2020, S. Beaty, V. Holland, 2M, 2F ( NCDWR); Nash Co., Swift Creek, SR 1310, 36.11167, -77.92111, 24 April 2003, E. Fleek, T. MacPherson, 11L ( NCDWR); Richmond Co., Naked Creek, SR 1003, 35.08197, -79.58909, 12 March 2019, C. Verdone, V. Holland, S. Beaty, 1L ( NCDWR); same location, 28 March 2019, emerged 4 April 2019, S. Beaty, C. Verdone, V. Holland, L. Housley, 2M, 2E ( NCDWR); same location, 28 March 2019, S. Beaty, C. Verdone, V. Holland, L. Housley, 5L ( NCDWR); Stokes Co., Little Yadkin River, SR 1104, 36.29888, -80.41388, 6 May 1987, D. Penrose, 1L ( NCDWR); Wake Co., unnamed tributary to Middle Creek, Optimist Farm Rd., 35.65831, -78.73863, 23 April 2019, C. Verdone, D. Fuller, 2M ( NCDWR); Yadkin Co., North Deep Creek, SR 1510, 36.12583, -80.59222, 12 April 1993, D. Lenat, K. Herring, T. MacPherson, 11L ( NCDWR); North Deep Creek, SR 1503, 36.17194, -80.67500, 12 April 1993, D. Lenat, K. Herring, T. MacPherson, 8L ( NCDWR).

Adult male, female, and ovum. Described in Szczytko & Kondratieff (2015).

Mature larva ( Figs. 1–4 ). Pre-emergent male larvae 4.9–5.5 mm (n = 6), female larvae 5.2–6.1 (n = 12). Body small and slender with contrasting body pattern ( Fig. 1 ). Body usually with inconspicuous clear clothing hairs, some specimens with darker hairs.

Dorsum of head ( Fig. 2 ). Ground color pale yellow with mottled brown mask and with a pale medial area anterior to median ocellus, a pair of large anterolateral pale spots, a pair of mediolateral pale spots, a small enclosed pale ocellar spot, and pale ocular areas; pale median area sub-trapezoidal and slightly wider anteriorly with anterior edge usually somewhat straight; fully enclosed interocellar spot triangular to subtriangular and reaching anterior ocellus, removed from lateral ocelli; frontoclypeus with additional semi-quadrate anterolateral pale areas; brown mask composed of an irregular median transverse stripe, lateral arms of stripe directed posteriorly from pale median area with an abrupt anterolateral turn to antennal base, similar to a bent arm; mask with posterior extensions to lateral ocelli; brown bar on anterior frontoclypeus with darker brown tentorial spots or dashes at vertices; area between eyes and lateral ocelli pale, mediolateral tentorial callosities brown, barely visible; occiput with irregular brown areas posterior to epicranial suture and on either side of the epicranial stem, stem overlaid with a triangular pale spot; an oblique brown stripe from the post-occipital margin reaching post ocular margin, spicules scattered along oblique stripe; labrum pale yellow with median area marginally darker, thinly edged with brown. Labrum yellow-brown, slightly darker basomedially. Antennal scape and pedicel yellow to yellow-brown, flagellum yellow with apical segments slightly darker; flagellum with 28–31 antennomeres (n=11); each segment with an apical circlet of small spines. Pale to brown clothing hairs covering head.

Maxilla ( Figs. 5–6 ). Lacinia bidentate, receding evenly from base to subapical tooth; a long thin marginal seta between apical and subapical tooth present, and often a second shorter seta present at base of subapical tooth; 6–7 striated, stout, socketed marginal setae below subapical tooth, setae progressively thinner and shorter towards base; anterior marginal setae barely smaller than subapical tooth giving lacinia an overall comb-like appearance; 2–3 thin, unevenly-spaced setae just below last marginal seta on palm edge; a submarginal row of 3 closely set striated, stout, socketed setae below apical tooth, a fourth smaller seta in-line but slightly removed posteriorly; ventral face of palm with 3–4 setae, some bifurcate at tip, most set away from palm edge. Length of striated apical tooth of lacinia approximately 1/3 the palm length (0.38X) and 2/3 the basal palm width (0.64–0.72X). Subapical tooth about 2/3 (0.63–.68X) the length of the apical tooth. Galea about 0.9X lacinial palm length, with a sparse ventral row of thin setae and tipped with 1–3 apical long spines. Maxillary palp stout, about 1.5X (1.53–1.58X) length of lacinia; segments 1–4 successively longer, segment 5 subequal to segment 3; palp segments 1 and 2 with transverse row of spinous setae at apex; segment 3 with 1–2 spines on body of segment and 1–2 apical spines, segment 5 tipped with 1–2 sensillae.

Mandibles ( Figs. 7–8 ). Right mandible ( Fig. 7 ) bicuspid, outer cusp with three teeth, ventral tooth largest, dorsal tooth smallest, tooth serrations indistinct or worn; ventral surface of mandible with an unorganized band of long spinous setae from base to outer ventral tooth, setae nearest ventral tooth thicker and with setules and serrations; inner cusp with three teeth, middle tooth longest and largest; a comb-like row of small sharply pointed acanthae at base of basal tooth, number and size of acanthae variable ( Fig. 7 inset); molar ridge with a dense row of spine-like setae, setae longer and thinner towards base of mandible; dorsal surface of mandible also with band of unorganized serrated setae from inner cusp towards base of mandible, setae near cusp larger and with setules. Left mandible ( Fig. 8 ) similar to right mandible except comb-like row of sharply pointed acanthae at base of inner cusp replaced by a dense brush of short spinous setae from basal tooth on inner cusp to molar ridge ( Fig. 8 inset).

Thorax ( Figs. 1–2 ). Pronotum ( Figs. 1–2 ) about twice as wide as long, extensive brown patterning consisting of two brown “O” shaped markings with pale centers, one on each disk, and connected by a narrow anterior transverse band; a brown stripe along the medial suture, widest posteriorly, joins to an anterior transverse brown bar forming a “ T ”; brown pronotal markings encompass many small dark rugosities; a narrow pale stripe on either side of the brown median stripe; pronotal flange edged in brown on anterior and posterior margins, narrowly interrupted medially, widely pale laterally; about 1/3 of anterior pronotal furrow pale; pronotum edged with closely set row of stiff setae, with longer bristles interspersed, the longest on lateral and posterior corners and approximately 1/8 the width of pronotum. Mesonotal and metanotal discs with irregular brown longitudinal markings ( Fig. 1 ); wing pads yellow-brown with one (mesonotum) or two (metanotum) faint longitudinal brown bands, inner stripe of metanotum widest posteriorly; lateral margins of nota fringed with a short, closely set row of stiff bristles, with intervening long bristles truncate, mesonotum additionally with a cluster of up to 10 longer stiff bristles on the anterolateral corners. Thoracic nota with sparse light brown to pale clothing hairs. Lateral aspect of thorax pale yellow with notal trochantins brown to dark brown at apex; procoxal process conspicuous, dark brown. Thoracic sterna pale, without distinctive markings; basisterna with short clear setae; furcal pits conspicuous, Y-stem arms inconspicuous. Entire sternum with pale to light brown clothing hairs.

Legs ( Fig. 9 ). Pale yellow to yellow-brown overall. Femoral-tibial ratio 0.9 to 1.0 for each leg (n = 12). Posterior face of femora with a sparse and uneven medial row of stout golden spines; anterior face of femora with golden spines scattered along length, with a row of short spines along posterior edge of sclerite; dorsal edge of femora with a cluster of bristles in apical half, longest bristles about half the width of corresponding femur, many bristles truncate; femora with silky setae very sparse to absent ( Fig. 9 ). Tibiae with two longitudinal dorsal rows of short spines and a sparse dorsal row of long silky setae along length, setae twice as long as width of tibia; tibiae also with two ventral rows of spines. Tarsi pale yellow-brown with a comb-like ventral row of stiff setae and a sparse dorsal row of silky setae. Two claws darker apically, moderately long and gradually curved.

Abdomen ( Figs. 1, 3–4 ). Terga yellow-brown with three dark brown longitudinal stripes, two lateral and one median, often bordered by obscure pale lines ( Figs. 1, 3 ); anterior half of each segment with a transverse row of eight small, variably dark dots, obscure in some specimens; posterior edges of each tergal sclerite bearing a transverse row of golden spines interspersed with long truncate to slightly clavate bristles, longest bristles about ¾ length of respective segment; terga also with a few curved erect setae on body of sclerite. Abdominal sterna ( Fig. 4 ) yellow-brown, darker than thoracic sterna; posterior edges of sterna bearing a transverse row of short golden spines, successively longer on distal segments; first and last dot of dorsal transverse row visible in ventral aspect on segments 9 and 10. Clothing hairs clear to light brown. Paraprocts triangular, pointed, 1.3–1.5X as long as wide. Cerci yellow-brown; each cercal segment with an apical circlet of spines, and bearing one long ventral spine about 2/3 length of respective segment and one dorsal spine about ½ length of segment; distal third of cerci with a sparse setal fringe, bearing 1–3 fine dorsal setae.

Diagnosis. The larval habitus of I. lenati is defined by the following combination of characters: small body size (4.9–6.1 mm, n = 12); head pattern with a pale medial area anterior to median ocellus with a straight anterior margin, a pair of large anterolateral pale areas, a small enclosed pale ocellar spot, a pair of mediolateral pale spots that are confluent with the lateral ocelli and pale ocular areas; each pronotal disc with a brown “O” marking; femora with a sparse to absent fringe of silky setae and with long truncate bristles in apical half; three dark longitudinal abdominal stripes bordered by pale lines. Additionally, the overall habitus of this species appears quite bristly.

Taxonomic notes. The larva of I. lenati is superficially most similar to I. davisi ( Figs. 10–14 ), with which it is sometimes sympatric. Both taxa have striped abdomens ( Figs. 3 , 13 ) and the same configuration of markings on the head and pronotum ( Figs. 2 , 12 ). The diagnostic characters listed above differ from I. davisi in the following: pale medial area anterior to median ocellus is pointed anteriorly in I. davisi ( Fig. 11–12 ), femora of I. davisi have long silky setae ( Fig. 10 ), and the abdominal stripes have more pronounced dark submedial stripes ( Fig. 13 ).

Figures

FIGURES 9–10. 9. Isoperla lenati, foreleg, dorsal, Flat Creek, Hoke Co., North Carolina. 10. Isoperla davisi, foreleg, dorsal, Sandy Creek, Randolph Co. North Carolina.

FIGURES 11–14. Isoperla davisi, larva, Lumber River Hoke/Scotland Co., North Carolina. 11. Habitus, dorsal. 12. Head and pronotum, dorsal. 13. Abdomen, dorsal. 14. Abdomen, ventral.

FIGURES 1–4. Isoperla lenati, larva, Flat Creek, Hoke Co., North Carolina. 1. Habitus, dorsal. 2. Head and pronotum, dorsal, (a) pale medial area anterior to median ocellus, (b) anterolateral pale spots, (c) mediolateral pale spots, (d) enclosed pale ocellar spot, (e) pale ocular areas. 3. Abdomen, dorsal. 4. Abdomen, ventral.

FIGURES 5–8. Isoperla lenati, larva, Rockfish Creek, Hoke Co., North Carolina. 5. Right lacinia, ventral. 6. Left lacinia, ventral. 7. Right mandible, ventral; (inset) acanthae. 8. Left mandible, ventral; (inset) a dense brush of short spinous setae.