Oemopteryx bimaculata, Verdone & Williams & Beaty & Holland & Grubbs & Dewalt, 2025

Verdone, Chris J., Williams, Bronwyn W., Beaty, Steven R., Holland, Victor B., Grubbs, Scott A. & Dewalt, Edward, 2025, The adults, larvae, and systematics of the Nearctic Oemopteryx Klapálek, 1902 (Plecoptera: Taeniopterygidae), Zootaxa 5595 (1), pp. 1-94 : 18-28

Oemopteryx bimaculata sp. nov. Verdone, Williams, Beaty & Holland

( Figs 7–12 )

Two-spotted Willowfly

Oemopteryx contorta : Stewart 2000:59. (in part)

Oemopteryx contorta : Grubbs 2006: 42.

Oemopteryx contorta : Verdone, Kondratieff, DeWalt & South 2017: 39 .

Etymology. This species is named for the pair of pale spots on tergum-1 present on both the adult male and female. The name combines the Latin prefix bi - meaning “two” and the Latin adjective macula and the past participle - ta meaning “spotted”. The name is used as an adjective of feminine gender. The common name “Two-spotted Willowfly” is proposed for this species.

Distribution. USA.—AL, GA, KY, TN, WV ( Fig. 6 ).

Material examined. Holotype M: USA.— Tennessee: Morgan Co., Hall Branch, Camp Austin Rd. , 36.03188, -84.56940, 15 February 2024, C. Verdone, L. Everett ( USNM) . Paratypes: USA.— Georgia: Dade Co., Daniel Creek, Cloudland State Park , 34.82457, -85.49074, 8 February 2017, C. Verdone, B. Kondratieff, 2M, 4F, 4L ( CSUIC). Tennessee: Bledsoe Co. , Henderson Creek , 4 mi NE Summer City, [ TN 235 ], [35.60689, -85.061514], 24 February 1999, B. Kondratieff, R . Kirchner, 3M, 1F, 19L ( CSUIC); Polebridge Creek , off TN 30 , Summer City , [35.57793, -85.11890], 24 February 1999, B. Kondratieff, R . Kirchner, 1M ( CSUIC). Cumberland Co., Clear [Creek], [Ridge Rd.], Lilly Bridge , [36.10204, -84.71717], 22 February 2007, C. R . Parker, 2F ( CSUIC); North Fork Elmore Creek , TN 298 , [36.10314, -84.94161], 9 February 1998, B. Kondratieff, R . Kirchner, 1M ( CSUIC); Obed River, [no location], [unable to approximate coordinates], 20 February 1976, B. Kondratieff, 1M, 6L ( CSUIC). Morgan Co., Green Branch of White Creek , Barnett Bridge Rd. , [36.14807, -84.77806], 9 February 1998, B. Kondratieff, R . Kirchner, 14M, 8L ( CSUIC); same location, 15 February 2024, C. Verdone, L. Everett, 1M, 26L ( NCDWR); same data, emerged 29 February 2024, 1M, 1E ( NCDWR); Hall Branch, Camp Austin Rd., 36.03188, -84.56940, 15 February 2024, C. Verdone, L. Everett, 1M, 1F ( NCDWR); Mud Lick Creek , TN 299 , Oakdale City Park , [35.98646, -84.55544], 9 February 1998, B. Kondratieff, R . Kirchner, 9M, 4F ( CSUIC); Smith Branch, Twin Bridge Rd. , 36.00640, -84.60735, 15 February 2024, C. Verdone, L. Everett, 1M, 1L ( NCDWR) .

Additional material: Kentucky: Harlan Co., Left Fork Martins Fork, Martins Fork WMA, 36.68261, - 83.41538, 14 April 2016, S.A. Grubbs, 1F ( WKUC); same data, 36.68423, -83.41434, 1F ( WKUC); same data, 36.68306, -83.41496, 3F ( WKUC). Tennessee: Bledsoe Co., [no waterbody], Summer City, [35.57417, -85.11611], 12 March 1964, H.B Cunningham, 3M, 1F ( INHS: Plecoptera 6257). Cumberland Co., [no waterbody], 2 miles south of Crossville, [unable to approximate coordinates], 12 March 1964, H.B Cunningham, 1M ( INHS: Plecoptera 6258); [no waterbody], 8 miles south of Crossville, [unable to approximate coordinates], 12 March 1964, H.B Cunningham, 2F ( INHS: Plecoptera 6259); Grundy Co., [no waterbody], Cumberland Heights, [35.40556, - 85.69667], 13 March 1964, H.B Cunningham, 1F ( INHS: Plecoptera 6254); same data, 1M ( INHS: Plecoptera 6255); same data, 1M ( INHS: Plecoptera 6256). Franklin Co., UT Little Coon Creek, off TN 16, Bear Hollow Mtn., 35.00451, -86.05228, 10 March 2024, S.A. Grubbs, 1M, 2F ( WKUC). Hamilton Co., [no waterbody], 4 miles NW of Chattanooga, [35.22753, -85.49190], 13 March 1964, H.B. Cunningham, 1M, 2F ( CNCI). Marion Co., North Prong Flat Fork, Frozen Head State Park, 36.13860, -84.48042, 27 February 2007, A.L. Sheldon, 2M, 1F ( WKUC); UT Cross Creek, 17 km NW South Pittsburg, Franklin-Marion State Forest, 35.08700, -85.86721, 12 February 2007, S.A. Grubbs, 2M, 1F ( WKUC); UT South Suck Creek, Rte 27, 5.2 km WNW Signal Mountain, Prentice Cooper State Forest, 35.14740, -85.39260, 31 January 2015, S.A. Grubbs, 2M ( WKUC); UT Sweeten Creek, 15 km NW South Pittsburg, Franklin-Marion State Forest, 35.08270, -85.83910, 12 February 2007, S.A. Grubbs, 2F ( WKUC). [no waterbody], 7 miles north of Whitwell, [unable to approximate coordinates], [no date], H.B Cunningham, 1F ( INHS: Plecoptera 6253). Morgan Co., Rock Creek, at Pilot Mountain, Hwy 27, [36.19849, -84.66061], 3 March 1977, K.E. Fullington, 1M ( INHS: Insect Collection 795636). Scott Co., UT New River, at Norma Rd. 2.8 air mi due S. of TN 63, [36.33986, -84.38591], 25 January 1997, B.A. Moody, 4L ( INHS: Insect Collection 795555). West Virginia: Mercer Co., [no waterbody], Flat Top, at Turnpike, [37.58119, -81.11834], 10 March 1959, H.H. Ross, C.A. Ross, 2F ( CNCI). Raleigh Co., Cherry Creek , at I-77, [37.67823 -81.11936], 18 February 1990, K.W. Stewart, 1M, 1F ( INHS: Insect Collection 795560).

Adult male ( Figs 7A , 8A ). Macropterous. Length of forewings 7.6–8.4 mm (n = 10). Length of body 7.2–8.4 mm (n = 10). General body color dark-brown.

Head ( Figs 7A , 8A ). Dorsum of head mostly dark-brown. Labrum pale anteriorly, brown posteriorly. Anterior frontoclypeus brown. Frons with a dark-brown U-shaped marking. Antenna longer than body. Scape, pedicel, and flagella dark brown. Scape with a distal notch on anterior face. First flagellum subdivided at distal 1/4. Rugosities anterolateral to lateral ocelli and ecdysial suture. Interocellar area uniformly dark-brown and slightly depressed. Occasionally with a pale stripe spanning area between eyes across lateral ocelli and interocellar space. Occiput with brown rugosities. Medial areas of the frons, interocellar surface, and occiput covered with fine, pale, clothing hairs.

Thorax ( Figs 7A , 8A ). Pronotum subquadrate, wider than long (length 0.8X width) with posterior width slightly wider than anterior width; brown overall with brown rugosities. Anterior and posterior margins of pronotal flange often pale. Disk with irregular brown rugosities; a transverse sinuous furrow at anterior 1/4. Prosternum moderately sclerotized. Meso- and metathorax dark-brown, heavily sclerotized dorsally and ventrally. Thoracic nota and coxae uniformly covered with sparse, short, fine clothing hairs. Legs with contrasting pigment. Femur pale, distal portion of femur dark brown. Tibia brown, dark brown on proximal and distal portions; apex of tibiae with 2-stout apical spines. Tarsus dark-brown. Legs uniformly covered with dark, short stout setae. Wings hyaline; venation brown. Forewing with light mottling; without costal crossveins between humeral crossvein and apex of the subcostal vein which may be forked. Hindwing mottling less developed, absent in anal region.

Abdomen. First abdominal tergite sclerotized with 2-submedial pale spots anteriorly, which may be contiguous medially and a thin pale posterior margin ( Fig. 7B ). Abdominal segments 1–9 lightly covered with short, fine clothing hairs. Terga 2–6 uniformly brown; terga 7–9 with a well-defined posteromedial membranous cleft; Sterna 2–8 with a pair of anterior sublateral oval brown spots. Sternum-9 with a lightly sclerotized broadly circular vesicle ( Fig. 8C ) that is attached to sternum-9 from directly beneath the vesicle. Sterna 7–8 lightly sclerotized. Sternum- 9 elongated into a scooped plate ( Fig. 9D ), width subequal from base to apex; apex square with rounded lateral margins ( Fig. 8C ); plate with numerous long setae on dorsal and ventral surfaces ( Figs 9A, 9D ); plate covering sternum-10 ventrally and extending beyond.

Terminalia ( Figs 9A–E ). Abdominal segment-10 nested within segment-9. Anterior margin unsclerotized. Tergal sclerite-10 with a subtle medial cleft and paired submedial flattened anterior processes with raised scale-like armature ( Figs 9A, 9C ). Cercus 3–4 segmented, excluding vestigial apical segment ( Figs 9A, 9D ) and with a low, rounded, posteriorly directed basalcercal process covered in socketed setae and sensilla basiconica ( Figs 9A–B, 9D–E ). Basal plate of tergum-10 relatively flat, sclerotized with a wrinkled texture ( Figs 9A, 9C ). Lateral struts present, median strut absent, but with a small medial point ( Figs 9A, 9C ). Basal bulb ( Figs 9A–B, 9E ), glabrous, oval, bulbous, moderately sclerotized and with an oval inner bulb bearing a small hollow stalk, which terminates at a pore on the anterior face near the junction of the 2-anterior epiproct processes. Anterior epiproct prong fused to basal bulb, divided halfway to base, each arm terminating a distal facing sclerotized foot-shaped process that it pointed at its apex and slightly recurved ventrally ( Figs 9A–B, 9D–E ). Posterior epiproct prong subdivided into 2-processes. Ventral process lightly sclerotized, divided near apex into 2-glabrous, rounded lobes ( Figs 9A–B, 9D–E ). Dorsal process pouch-like, armed with posteriorly directed spine-like setae with an apical sleeve containing 2–3 internal filaments that are not eversible ( Figs 9A–B, 9D–E ); filaments sometimes visible on left side of basal bulb. Paraprocts subdivided into two parts, symmetrical anterior paraprocts and asymmetrical bi-lobed posterior paraprocts. Anterior paraproct, conical, medially directed, evenly tapering to a point ( Figs 9A–B ). Posterior paraprocts ( Fig. 9A ) subdivided, fused at base. Left outer prong short, flattened and lightly sclerotized. Left inner prong long, flattened, twisted and striated, terminating with an acute sclerotized spine. Right outer prong flattened and moderately sclerotized. Right inner prong tubular, twisted and striated, tapering to apex.

Adult female ( Fig. 8B ). Macropterous. Length of forewings 9.6–9.7 mm (n = 10). Length of body 8.4–8.7 mm (n = 10). General body color brown. Overall appearance similar to male. Forewing with light mottling; without costal crossveins between humeral crossvein and apex of the subcostal vein which may be forked ( Fig. 8D ). AA1 vein of forewing with short fine setae ≤ 0.5mm ( Fig. 8F ). Hindwing mottling less developed, absent in anal region. ( Fig. 8D ). First abdominal tergite sclerotized with 2-submedial pale spots anteriorly, which may be contiguous medially and a thin pale posterior margin ( Fig. 7C ); terga 2–8 uniformly brown dorsomedially; terga 9–10 sclerotized dorsally and laterally. Lateral margins of abdomen segments 1–8 unsclerotized. Sternum-8 weakly sclerotized ( Fig. 8E ). Subgenital plate weakly sclerotized ( Fig. 8E ) with a U-shaped notch and a lightly sclerotized medial tab, which may be enfolded ( Fig. 10B ). Sternum-9 parabolic, produced just beyond the apex of abdominal segment-10 ( Figs 8E ; 10A ); length of free portion of sternum-9 0.8X basal width; uniformly covered with long setae that become longer posteriorly; lateral margins slightly narrowing to a broadly rounded apex ( Fig. 8E ). Cercus 5–6 segmented, excluding vestigial apical segment ( Figs 8E , 9A ).

Ovum. Unknown.

Mature larva ( Fig. 11A ). Length of male body 6.7–7.0 mm (n = 10), female body 7.2–8.0 mm (n = 10). General color light-brown. Integument glossy, much of the body with sparse, fine, hair-like sensillae and socketed stout setae, observable at>100X magnification. Specimens generally preserve in a curled posture with the head touching or approaching the abdomen apex, similar to other Taeniopterygidae .

Head ( Fig. 11A ). Dorsum of head light-brown with darker brown maculations variously developed.Antelabrum light-brown; anterior margin with a dense brush of golden setae. Postlabrum light-brown.Anterior frontoclypeus pale to light-brown. Frons with a brown U-shaped marking with posterolateral extensions; light-brown subrectangular markings directly anterior to lateral ocelli. Interocellar area diffusely light-brown, pale at junction of ecdysial suture. Occipital area diffusely light-brown and with irregular brown rugosities. Eyes with pigmented ommatidia reduced, not reaching eye margins. Antennal scape, pedicel and flagella brown; dorsobasal apically inserted setae absent ( Fig. 11C ); antenna slightly shorter than body ( Fig. 11A ).

Maxilla ( Figs 12A–B ). Lacinia triangular with a straight or slightly convex inner margin. Lacinia with 2-apical, cupped teeth and 2–5 subapical denticles on ventral face ( Fig. 12B square inset). Apical teeth subequal in length; relative length of apical teeth to palm length difficult to discern due to wear. Inner palm margin with 19-stout socketed marginal setae below apical teeth; first marginal seta robust. Basal 1/3 of palm with a cluster of>10 thin dorsal setae. A single acutely pointed sensilla basiconica on palm surface near the basal 1/5. Galea with a dense brush of curved setae on the distal apical margin, which transition to sparse peg-like setae at the apical 1/4; a thin patch of setae on inner margin below apical setae, which extends about halfway to base. Length of galea, including apical setae, 1.1X length of lacinia; width of galea 1.1X the lacinia width. Maxillary palp with 5-segments; 1.9X length of lacinia; palp with sensilla basiconica sparsely scattered over entire surface.

Mandible. Right mandible ( Fig. 12C ) bicuspid, outer cusp with 3-teeth, inner cusp with 1-tooth. Molar pad adorned with marginal rows of pointed acanthae (length 2.1X width). Palm dorsum with 1–9 dorsal sensillae adjacent to molar pad (requires focusing through the mandible) ( Fig. 12C circle inset); the proximal basal corner with a marginal patch of 3-hair-like, branched setae. Ventro-apical setal patch extending from outer cusp to beyond the inner cusp basally (indicated by dotted line in Fig. 12C ). Left mandible ( Fig. 12D ) bicuspid, outer cusp with 5- teeth, inner cusp with 1-broad concave tooth. Molar pad with marginal rows of rounded acanthae and long pointed acanthae (length 4.0X width). Palm dorsum with 1–7 sensillae adjacent to molar pad (requires focusing through the mandible) ( Fig. 12D circle inset); the proximal basal corner with a marginal patch of 5-hair-like, branched setae. Ventro-apical setal patch extending from outer cusp to beyond the inner cusp basally (indicated by dotted line in Fig. 12D , square inset).

Thorax ( Fig. 11A ). Pronotum wider posteriorly; light-brown with faint rugosities and a pale posteromedial spot. Length of forewing pad 3.3X width. Length of hindwing pad 1.8X width. Venter of thorax pale. Prothoracic presternum mostly glabrous with light-brown spicules laterally and a pair of elongate lateral cervical sclerites. Prothoracic basisternum and furcasternum light-brown; spicules dense medially and sporadic distally. Mesothorax with an oval prefurcasternal pit; light-brown spicules present both anterior and posterior to pit; lateral areas glabrous. Mesothoracic basisternum with light-brown spicules mostly concentrated medially. Furcasternal pit present between mesothoracic legs; furcasternum triangular, as long as wide (length 1.0X width). Metathoracic basisterna with a medial patch of light-brown spicules and a pair of furcasternal pits. Anterior face of femur generally pale with some darker pigment on the distal and dorsal margins ( Fig. 11D ). Femur and tibia with a dorsal fringe of silky setae (not shown); length of femoral setae less than 1/2 the width of the femur; length of tibial setae about equal to tibial width. Anterior and posterior faces of the femur with scattered short stout setae. Tibia pale; tibial callus and tibia apex darkened ( Fig. 11D ). Tarsus with a sparse dorsal fringe of silky setae (not shown); tarsus light-brown and becoming progressively darker distally. Venter of tibia and tarsus with scattered short stout setae.

Abdomen. Dorsum of abdomen usually with contrasting pigmentation, dark anteriorly and lighter posteriorly, most pronounced on terga 6–10 ( Fig. 11E ). Posterior margins of terga with a single row of short, stout sensillae. Posterior margins of tergum-8 and tergum-9 with a pair of thin, erect, submedial setae. Venter of abdomen pale; sterna 1–8 with light-brown spicules. Sternum-9 with an elongate plate (male = length 1.5X width; female = length 1.5X width); plate width relative to sternal width (male = 0.9X; female = 0.8X). Male plate ( Fig. 11F ) with sides slightly widening towards posterior margin of sternum-9, posterolateral margins convex, evenly rounded towards apex. Female plate ( Fig. 11G ) narrower basally, widest at posterior margin of sternum-9; posterolateral margins convex, evenly narrowing towards apex. Plates of both males and females with stout setae sparse on basal half, becoming denser towards apex. Cercus uniformly brown ( Fig. 11A ); dorsobasal apically inserted setae absent ( Fig. 11B ); cercus about as long as body ( Fig. 11A ).

Diagnosis. Oemopteryx bimaculata sp. nov. is defined in the adult male by the paired anterior processes on tergum- 10 in combination with two pale spots on the dorsum of abdominal tergum-1, which the female also possesses. The larvae are usually separable from O. contorta by the distinctly banded abdominal terga. The larvae differ from O. tuscarora sp. nov. by their darkened tibial callus, a character that is shared by O. contorta .

Type locality ( Fig. 13A ). Located in the Southwestern Appalachians Level III ecoregion in Morgan County, Tennessee, Hall Branch drains the west side of Lone Mountain (771 m) and is a tributary to the Emory River . The collection site is 304 m ASL and has a drainage area of 6.42 km 2. Substrate consists primarily of flat boulders and cobbles. The stream is well forested with much of the watershed residing in Lone Mountain State Forest . Water quality at the type locality has not been assessed .

Biological notes. Oemopteryx bimaculata sp. nov. is apparently endemic to the Appalachians with records known from the Southwestern Appalachians and Central Appalachians Level III ecoregions ranging from northeastern Alabama to southern West Virginia. Its most northeasterly records are within the Dissected Appalachian Plateau Level IV ecoregion, a potential basis for to delineate the ranges of the new species and O. contorta . The two species are apparently allopatric and although O. contorta is also found in the Central Appalachians, it occurs north and east of Dissected Appalachian Plateau Level IV ecoregion. Elevations of collection locations range between 238 m to 667 m ASL. Larvae have been collected from streams with drainage areas ranging from 3.9 km 2 to 16.8 km 2. Available records suggest adults are active from late January to mid-April.A conservation rank of G3 was calculated for this species indicating a moderate risk of extinction or collapse due to a somewhat restricted range, relatively few populations, or other factors (NatureServe 2020).

Figures

FIGURE 6. Distribution map of the Oemopteryx contorta Group species. Records include examined material, BOLD records included in genetic analysis and unpublished data from the CNCI.

FIGURE 7. Oemopteryx bimaculata sp. nov., Hall Creek, Morgan Co., Tennessee, adults. A. Live male. B. Male tergum one, dorsal. C. Female tergum one, dorsal. [morphological abbreviations: see Table 1].

FIGURE 8. Oemopteryx bimaculata sp. nov. adults., A–C. Hall Creek, Morgan Co., Tennessee. A. Male habitus, dorsal. B. Female habitus, dorsal. C. Male sterna, ventral. D. Daniel Creek, Dade Co., Georgia, female wings. E–F. Hall Creek, Morgan Co., Tennessee. E. Female sterna, ventral. F. Female forewing, lateral. [morphological abbreviations: see Table 1].

FIGURE 9. Oemopteryx bimaculata sp. nov., Green Branch, Morgan Co., Tennessee, adult male. A. Terminalia, dorsal. B. Terminalia, close, dorsal. C. Abdominal terga, dorsal. D. Terminalia, lateral. E. Epiproct, lateral. [morphological abbreviations: see Table 1].

FIGURE 10. Oemopteryx bimaculata sp. nov., Daniel Creek, Dade Co., Georgia, adult female. A. Abdominal sterna, ventral. B. Subgenital plate. [morphological abbreviations: see Table 1].

FIGURE 11. Oemopteryx bimaculata sp. nov., Green Branch, Morgan Co., Tennessee, larva. A. Habitus, dorsal. B. Right cercus, lateral. C. Right antenna, lateral. D. Legs, anterior. E. Abdomen, dorsal. F. Male sterna, ventral. G. Female sterna, ventral. [morphological abbreviations: see Table 1].

FIGURE 12. Oemopteryx bimaculata sp. nov., Henderson Creek, Bledsoe Co., Tennessee, larval mouthparts, ventral. A. Right lacinia, galea and maxillary palp. B. Left lacinia, galea and maxillary palp; subapical denticles (square inset). C. Right mandible; dorsal sensillae (circle inset). D. Left mandible; ventro-apical setal patch (square inset); dorsal sensillae (circle inset). [morphological abbreviations: see Table 1].

FIGURE 13. Oemopteryx bimaculata sp. nov., site photos. A. Type locality, Hall Creek, Morgan Co., Tennessee. (Photo credit: Larry Everett). B. Paratype locality, Green Branch, Morgan Co., TN. C. Paratype locality, Daniel Creek, Dade Co., Georgia.