Oemopteryx fosketti ( Ricker, 1965 )

Oemopteryx fosketti ( Ricker, 1965) View in CoL

Figs (28–32)

Saskatoon Willowfly

Brachyptera fosketti Ricker, 1965: 475 View in CoL . Holotype male (CNCI), [Clarkboro Ferry], Saskatchewan, Canada.

Brachyptera zelona Ricker, 1965: 477 View in CoL . Holotype male (INHS), Plecoptera View in CoL 1584; [Duchesne River] Myton, Duchesne Co., Utah, USA. Syn. Zwick, 1973: 313.

Oemopteryx fosketti View in CoL : Zwick 1973: 313.

Oemopteryx fosketti View in CoL : Dosdall & Lehmkuhl 1979: 23.

Oemopteryx fosketti View in CoL : Kondratieff & Baumann 2002: 392.

Oemopteryx fosketti View in CoL : Stewart & Oswood 2006: 107.

Oemopteryx fosketti View in CoL : Kondratieff & Baumann 2009b: 221.

Oemopteryx fosketti View in CoL : Dosdall & Giberson 2014: 217.

Distribution. Canada —AB, MB, SK. USA.—CO, MT, ND, UT ( Fig. 27 View FIGURE 27 )

Material examined. Canada — Alberta: Athabasca Co., Athabasca River, Athabasca , [54.72233, -113.28583], 7 April 1999, E. Fuller, 12M, 1F ( CSUIC) GoogleMaps . City of Edmonton, Edmonton, North Saskatchewan River , [53.53990, - 113.48193], 10 April 1993, E. Fuller, 10M, 3F ( CSUIC) GoogleMaps . USA.— Colorado: Mesa Co., Dolores River, [Hwy 121] at Gateway , [38.68051, -108.98019], 3 March 1990, B. Kondratieff, J. Welch, 26M, 12F, 16L ( CSUIC); same location, 17 March 2011, B. Kondratieff, R GoogleMaps . Durfee , 1M ( CSUIC) . Moffat Co., Yampa River , Deerlodge [Park Campground] ,

Dinosaur National Monument , [40.44637, -108.51164], Nelson, Anderson, 5M, 1F ( CSUIC) GoogleMaps . Montezuma Co., San Juan River, Hwy 160, Four Corners , [37.00245, -109.03225] March 2001, B. Kondratieff, 7F ( CSUIC) GoogleMaps . Montrose Co., Dolores River, [Hwy 141] at Mesa Creek , [38.43767, -108.83944], 3 March 1990, B. Kondratieff, J. Welch, 4M, 1F, 17L ( CSUIC) GoogleMaps ; Dolores River, at Bedrock [Hwy 90], [38.31048, -108.88575], 3 March 1990, B. Kondratieff, J. Welch, 8M, 4F ( CSUIC) GoogleMaps . North Dakota: Billings Co., Little Missouri River , Medora , [46.916613, -103.53161], 9 March 1998, C. Milue, 3M, 1F ( CSUIC) GoogleMaps . Utah: Grand Co., Colorado River, Hwy 128, mi 4.5, [38.62413, - 109.51324], 9 March 1995, S. Fitzgerald, A. Foley, 20F ( CSUIC) GoogleMaps . San Juan Co., San Juan River, Hwy 191, Sand Island Campground, 37.25812, -109.61926, 11 March 2017, C. Verdone, F. Lichtner, 1F ( CSUIC) GoogleMaps . Wyoming: Big Horn Co., Big Horn River, Hwy 30 at Basin , [44.38146, -108.03502], 10 March 2000, B. Kondratieff, Doyle, 1M ( CSUIC) GoogleMaps . Carbon Co., Medicine Bow River , CR 291 at gauging station, [42.01006, -106.51310], 7 March 2006, D. Rees, 1M ( CSUIC) GoogleMaps . Johnson Co., South Fork Powder River , I-25 at mile marker 246, [43.62865, -106.5724], 16 April 2010, B. Kondratieff, R. Durfee, 8F ( CSUIC) GoogleMaps . Sheridan Co., Goose Creek, Fort [Rd.], Sheridan , [44.82108, -106.96170], 15April 2015, B. Kondratieff, R. Durfee, 1F ( CSUIC) GoogleMaps .

Adult male ( Fig. 28A View FIGURE 28 ). Forewing brachypterous. Length of forewings 1.9–2.5 mm (n = 10). Length of body 8.1–8.9 mm (n = 10). General body color brown to dark-brown.

Head ( Fig. 28A View FIGURE 28 ).Dorsum of head mostly dark-brown.Labrum pale anteriorly, brown submedial spots posteriorly. Anterior frontoclypeus light-brown. Frons brown with a dark-brown U-shaped marking. Antenna longer than body. Scape, pedicel, and flagella yellow-brown to dark brown. Scape with a distal notch on anterior face. First flagellum subdivided at distal 1/4. Triangular raised rugosities anterolateral to lateral ocelli and ecdysial suture. Interocellar area uniformly dark-brown and slightly depressed. Occiput with dark brown rugosities. Medial areas of the frons, interocellar surface, and occiput covered with fine, pale, clothing hairs.

Thorax ( Fig. 28A View FIGURE 28 ). Pronotum subquadrate, wider than long (length 0.8X width) with posterior width marginally wider than anterior width; brown overall with darker rugosities. Outer margins of pronotal flange often pale. Disk with irregular dark rugosities. Prosternum moderately sclerotized. Meso- and metathorax brown, heavily sclerotized dorsally and moderately sclerotized ventrally. Thoracic sterna and coxae uniformly covered with short, fine clothing hairs and longer brown setae. Legs brown, generally concolorous. Femur with an incomplete mottled brown stripe on the anterodorsal and posterodorsal faces. Tibia brown; apex of tibiae with 2-stout apical spines. Tarsus brown. Legs uniformly covered with dark, short stout setae. Wings hyaline; venation yellow-brown to brown; mottling absent. Forewing brachypterous, extending to at least the posterior margin of tergum-1; apex of forewing acutely pointed or rounded; upturned portion of forewing>1/3 total wing length. Hindwing extending beyond abdominal segment-10; pleated anal region absent.

Abdomen. Abdominal terga and sterna 1–9 uniformly brown. Abdominal segments 1–9 lightly covered with short, brown setae. Sterna 2–8 with a pair of anterior sublateral oval brown spots. Terga 6–9 with a concave anterior margin. Vesicle absent on sternum-9 ( Fig. 28C View FIGURE 28 ). Sternum-9 elongated into a scooped plate ( Fig. 29D View FIGURE 29 ), width widest at mid-length, apex broadly rounded, overall shape circular, ventrally ( Fig. 28C View FIGURE 28 ); dorsally, apex broadly rounded medially and enfolded anteriorly; plate with numerous long setae on dorsal and ventral surfaces ( Figs 28C View FIGURE 28 ; 29A, D View FIGURE 29 ); plate covering sternum-10 ventrally and extending beyond.

Terminalia ( Figs 29A–E View FIGURE 29 ). Abdominal segment-10 nested within segment-9. Tergal sclerite-10 moderately sclerotized with a heavily sclerotized medial cleft ( Fig. 29C View FIGURE 29 ); paired anterior processes absent. Cercus 5–7segmented, excluding vestigial apical segment ( Figs 29A, 29D View FIGURE 29 ), and with a small, finger-like, posteriorly directed basalcercal process covered in socketed setae and sensilla basiconica ( Figs 29A, 29D–E View FIGURE 29 ). Basal plate of tergum-10 slightly produced dorsally, sclerotized with a medial furrow ( Fig. 29A View FIGURE 29 ). Lateral struts present, median strut present ( Fig. 29A View FIGURE 29 ). Basal bulb fused to anterior epiproct, covered in minute raised armature ( Figs 29A–B, 29E View FIGURE 29 ), 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 apex of the anterior epiproct. Anterior epiproct dorsoventrally flattened, widening laterally towards apex; apex with a rounded medial projection that is>1/3 epiproct width ( Figs 29A–B View FIGURE 29 ). Posterior epiproct prong divided near apex into dorsal and ventral processes ( Figs 29A–B, 29D–E View FIGURE 29 ). Apex of ventral process with a pair of bulbous lobes that are deeply divided medially, sclerotized ventrally and membranous with scale-like setae dorsally ( Figs 29A–B View FIGURE 29 ). Dorsal process pouch-like, armed with posteriorly directed spine-like setae with an apical sleeve containing 2-internal eversible filaments; filament(s) generally not visible inside of basal bulb. Paraprocts subdivided into 2-parts, symmetrical anterior paraprocts and asymmetrical multi-lobed posterior paraprocts.Anterior paraproct, sub-rectangular medially directed, narrowing apically to a truncate apex with a rounded anterior margin and angulate posterior margin ( Fig. 29A View FIGURE 29 ). Posterior paraprocts ( Fig. 29A View FIGURE 29 ) with 3-prongs, variously fused. Left outer prong broad, flat, concave posteriorly, apex scoop-shaped, directed anteriorly. Left middle prong projecting from the posterior proximal edge of outer prong, twisted, flat, lightly sclerotized, concave anteriorly, apex scoop-shaped. Left inner prong a sclerotized ridge bearing ~20 long stout golden setae, arising from the base on the posterior face of the posterior paraproct. Right outer prong, moderately sclerotized, C-shaped laterally, with a round, distally recurved apical projection. Right middle prong projecting from the posterior proximal edge of the right outer prong, tubular, twisted and tapering to apex. Right inner prong a raised sclerotized ridge bearing ~20 long stout golden setae.

Adult female ( Fig. 28B View FIGURE 28 ). Macropterous. Length of forewings 11.6–12.1 mm (n = 10). Length of body 6.2–8.5 mm (n = 10). General body color brown. Overall appearance similar to male. Wings hyaline; mottling absent. Forewing without costal crossveins between humeral crossvein and apex of the subcostal vein which may be forked ( Fig. 28D View FIGURE 28 ). AA1 vein of forewing with long fine setae ≥1.0 mm ( Fig. 28F View FIGURE 28 ). Hindwing mottling absent ( Fig. 28D View FIGURE 28 ). Lateral margins of abdomen unsclerotized. Sternum-8 sclerotized laterally ( Fig. 28E View FIGURE 28 ). Subgenital plate lightly to moderately sclerotized medially ( Fig. 28E View FIGURE 28 ); moderately produced posteriorly; posterior margin typically with a shallow medial concavity ( Figs 28E View FIGURE 28 , 30A–B View FIGURE 30 ). Sternum-9 produced just beyond the paraproct bases; free portion of sternum (length 1.0X width); uniformly covered with long setae that become longer posteriorly; lateral margins slightly narrowing to a rounded apex. Cercus 7–8 segmented, excluding vestigial apical segment ( Figs 28E View FIGURE 28 , 30A View FIGURE 30 ).

Ovum. Unknown.

Mature larva ( Fig. 31A View FIGURE 31 ). Length of male body 7.3–8.4 mm (n = 6), female body 9.6–10.9 mm (n = 6). General color light-brown to yellow. 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, rarely with the head touching or approaching the abdomen apex.

Head ( Fig. 31A View FIGURE 31 ). Dorsum of head light-brown with darker brown maculations variously developed.Antelabrum light-brown; anterior margin with a dense brush of golden setae. Postlabrum pale. Anterior frontoclypeus pale; brown subrectangular markings directly anterior to lateral ocelli. Interocellar area diffusely light-brown, pigment extends anterolateral of median ocellus; pale area at junction of ecdysial suture. Occipital area diffusely light-brown and with irregular brown rugosities. Eyes with pigmented ommatidia reduced, not reaching eye margins. A single long seta both anterior and posterior to eyes. Scape, pedicel and flagella pale yellow-brown; dorsobasal apically inserted setae present ( Fig. 31C View FIGURE 31 ); antenna slightly shorter than body ( Fig. 31A View FIGURE 31 ).

Maxilla ( Figs 32A–B View FIGURE 32 ). Lacinia triangular with a straight inner margin. Lacinia with 2-apical, cupped teeth and 2–4 subapical denticles on ventral face.Apical teeth subequal in length; relative length of apical teeth to palm length difficult to discern due to wear. Inner palm margin with 11-stout socketed marginal setae below apical teeth; first marginal seta robust. Basal 1/3 of palm with a cluster of>10 thin dorsal setae. Acutely pointed sensilla basiconica below apical teeth and on inner palm margin near the middle. 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; 2.2X length of lacinia; palp sensilla basiconica on distal and apical margins.

Mandible. Right mandible ( Fig. 32C View FIGURE 32 ) bicuspid, outer cusp with 2–3 teeth, inner cusp with 1-tooth. Molar pad adorned with marginal rows of truncate acanthae (length 1.0X width). Palm dorsum with 4–6 dorsal sensillae adjacent to molar pad (requires focusing through the mandible) ( Fig. 32C View FIGURE 32 circle inset); the proximal basal corner with a marginal patch of 3–5 hair-like, branched setae. Ventro-apical setal patch extending from outer cusp to beyond the inner cusp basally (indicated by dotted line in Fig. 32C View FIGURE 32 ). Left mandible ( Fig. 32D View FIGURE 32 ) bicuspid, outer cusp with 4-teeth, inner cusp with 1-triangular tooth. Molar pad with marginal rows of rounded acanthae and long pointed acanthae (length 4.5X width). Ventral face of molar pad with 6–9 conical acanthae on ( Fig. 32D View FIGURE 32 square inset). Palm dorsum with 1–2 dorsal sensillae adjacent to molar pad (requires focusing through the mandible) ( Fig. 32D View FIGURE 32 circle inset); the proximal basal corner with a marginal patch of 4–5 hair-like, branched setae. Ventro-apical setal patch extending from outer cusp to beyond the inner cusp basally (indicated by dotted line in Fig. 32D View FIGURE 32 ).

Thorax ( Fig. 31A View FIGURE 31 ). Pronotum marginally wider posteriorly; light-brown with faint rugosities and a pale posteromedial spot. Length of forewing pad male = 1.7 X; female = 3.9X width. Length of hindwing pad male = 2.4X; female = 2.3X width. Venter of thorax pale. Prothoracic presternum mostly glabrous with a pair of elongate lateral cervical sclerites. Prothoracic basisternum and furcasternum light-brown; spicules if present, indistinct. Mesothorax with an oval prefurcasternal pit. Mesothoracic basisternum with light-brown spicules mostly concentrated medially. Furcasternal pit present between mesothoracic legs; furcasternum triangular, wider than long (length 0.5X width). Metathoracic basisterna with a pair of furcasternal pits. Femur and tibia generally pale ( Fig. 31D View FIGURE 31 ) and with a fringe of silky setae (not shown); length of femoral setae less than 1.5X the width of the femur; length of tibial setae about 1.4X tibial width. Anterior and posterior faces of the femur with scattered short stout setae. Tibial callus pale ( Fig. 31D View FIGURE 31 ). Tarsus with a sparse dorsal fringe of silky setae (not shown); tarsus pale ( Fig. 31D View FIGURE 31 ). Venter of tibia and tarsus with scattered short stout setae.

Abdomen. Dorsum of abdomen uniformly light-brown ( Fig. 31E View FIGURE 31 ). Posterior margins of terga with a single row of short, stout sensillae. Posterior margins of terga 8–10 with a pair of thin, erect, submedial setae. Venter of abdomen pale; sterna 7–8 lacking conspicuous sensillae ( Fig. 31F View FIGURE 31 ); Sternum-9 with an elongate plate (male = length 1.4X width; female = length 1.5X width); plate width relative to sternal width (male = 0.8X; female = 0.8X). Male plate ( Fig. 31G View FIGURE 31 ) with sides slightly widening towards posterior margin of sternum-9, posterolateral margins convex, evenly rounded towards apex. Female plate ( Fig. 31H View FIGURE 31 ) 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 pale yellow-brown; dorsobasal apically inserted setae present ( Fig. 31B View FIGURE 31 ); cercus about as long as body ( Fig. 31A View FIGURE 31 ).

Diagnosis. Oemopteryx fosketti is defined in the adult male by the lack of a vesicle, brachypterous forewings, the upturned portion of forewing being>1/3 total wing length, the medial apical lobe of anterior epiproct being>1/3 epiproct width, the apical lobes of posterior epiproct being divided by a deep furrow and the free portion of sternum-9 being circular ventrally. The female is distinguished by having long fine setae ≥ 1mm extending to the base of AA1 vein. The larvae are defined by having a pale third tarsal segment, and abdominal sterna 7–8 lacking conspicuous sensillae.

Taxonomic notes. The larva of O. fosketti was first described by Dosdall & Lehmkuhl (1979) from specimens collected in Saskatchewan, Canada. They described the larva as being dark brown to nearly black, which is apparently incorrect or an eco-phenotype. Their material, while abundant, consisted of emergent larvae, in which adult characters including coloration can be seen through the larval cuticle. Their illustration of the antennal scape (fig. 155) shows dark pigment laterally. Among the material examined in the current study this pigment was only observed in late instar larvae and was developed beneath the larval cuticle, which we concluded was adult pigmentation. Care should be taken when using the larval sternal sensillae character as adults will have sensillae in these locations. However, if viewed laterally, adult characters will be observed to be beneath the larval cuticle.

Biological notes. Oemopteryx fosketti is endemic to the uplands, plateaus, and plains associated with the Rocky Mountains. Records are known from the Four Corners area of Arizona, Colorado, New Mexico and Utah north to Saskatchewan and Alberta, Canada. Elevations of collection locations range between 466 m to 1957 m ASL. Based on known records, O. fosketti appears to be allopatric with O. glacialis with which it is most similar morphologically. Available records indicate adults are active from early March to late April. Larvae have been collected from streams with drainage areas ranging from 11,292 km 2 to 35,601 km 2. Dosdall & Lehmkuhl (1979) documented several life history strategies for the species in Saskatchewan including protandry and fully mature eggs in emergent female larvae. They also hypothesized a univoltine life cycle with larval diapause for O. fosketti . NatureServe (2024) has assigned this species a conservation rank of G5, defined as having a low risk of extinction due to its wide ranging distribution and little concern from populations declines, or threats to habitat.