Orthonevra atlantica, Żóralski & Meutter & Mengual & Gadawski, 2024

Żóralski, Robert, Meutter, Frank Van De, Mengual, Ximo & Gadawski, Piotr, 2024, Two Palaearctic species of Orthonevra (Diptera: Syrphidae) under the name O. brevicornis, Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) 64 (1), pp. 223-242 : 225-229

Orthonevra atlantica

Żóralski & Van de Meutter, sp. nov.

( Figs 1A–B , 2A–B , 3A , 4A , 5A–C , 7A–E )

Type material. HoLoTYPF: J ( Figs 1A , 2B , 4A , 5A, 5B, 5C , 7A ), labelled “20159 // Polska CF16 // Kartoszyno // on Crataegus spp. // 3 VI 2021 // R. Żóralski leg.” and with our red holotype label “ HOLOTYPE J // Orthonevra atlantica // Żóralski & Van de Meutter, 2024 “. Deposited in ZMHB. PARATYPFs: 61 JJ 14 ♀♀, all bearing our yellow paratype label: BELGIUM: Liège, univ. Sart Tilman, 1979, 1 J, leg. A. Pauly ( RBINS); Oud-Heverlee, 28.iv.1999, 1 J ( Fig. 7E ), leg. FM ( FMTB); Engsbergen, Achterheide, 22.v.2011, 1 J, leg. FM ( FMTB); Assent, Papenbroek, 5.–19.iv.2012, 1 J, Malaise trap, leg. FM ( FMTB); Torgny, reservaat, 10.iv.2015, 1 J, leg. FM ( FMTB); Halma, Route Napoleon B, 8.iv.2017, 1 J, leg. FM ( FMTB); Froidfontaine, Tanton, 6.v.2017, 1 J, leg. FM ( FMTB); Teuven, Bos, 2.v.2018, 1 J, leg. FM ( FMTB); Bertrix, Rue de Muno, 22.iv.2019, 1 J, leg. FM ( FMTB); Buzenol, Montauban, 29.v.2020, 2 JJ (GenBank acc. no. OR859731), leg. FM ( FMTB); Ovifat, Reinhardstein, 9.v.2021, 1 J (GenBank acc. no. OR859711), leg. FM ( FMTB); Bertrix, Rue de Muno, 16.iv.2022, 1 J (GenBank acc. no. OR859697), leg. FM ( RBINS). CZECH REPUBLIC: Jívová, u Dómského lesa, 540 m, on flowering Crataegus sp. , 27.v.2017, 5 JJ, leg. L. Mazánek (3 JJ LMJC, 2 JJ RZRP), 28.v.2017, 1 J, leg. L. Mazánek ( LMJC). GERMANY: Prov.Brandenbg., [no date], 1 J ( ZMHB, ex. coll. Mehr); Niedersachsen, Harz-Südrand Hirseteich, 1 km NW Walkenried, 19.v.2002, 2 JJ, leg. Stuke ( ZFMK); Niedersachsen, Harz, Oberaue Zwischen Breitenbach und Unterzorge, 31.v.2003, 1 J, leg. Stuke ( ZFMK); Schleswig-Holstein, Kreis Ostholstein, Glinde südlich Schonwalde am Bungsberg, 54.1773N 10.7536E, 27.v.2016, Malaise trap, 1 ♀ (GenBank acc. no. OR859649), leg. GBOL-team, ZFMK-TIS-2608557 ( ZFMK); Schleswig-Holstein, Kreis Ostholstein, Erlenbruch am Masselberg bei Schwienkuhl, 54.2342N 10.9154E, 3.vi.2016, Malaise trap, 1 ♀ (GenBank acc. no. OR859696), leg. GBOL-team, ZFMK-TIS-2608415 ( ZFMK). NETHERLANDS: GE – Beek, Smorenhoek, 1.v.2009, 1 J, leg. W. van Steenis ( WSBN); ZH – Nieuwkoopse Plassen, kano aanlegplaats, 14.v.2017, 1 J, leg.W. van Steenis ( WSBN). POLAND: ♀ ( Figs 1B , 7B ) labelled “22154 // Polska CF16 // Kartoszyno // on Crataegus spp. // 4 VI 2022 // R. Żóralski leg.” and with our yellow paratype label “ PARATYPE (ALLOTYPE) ♀ // Orthonevra atlantica // Żóralski & Van de Meutter, 2024 ”; caught in copula with a male paratype, on the same Crataegus sp. as the holotype, but in the following year; it is on the same pin as the male paratype and deposited in ZMHB; Niemcza [= Nimpsch Schles. Duda; O. plumbago Lw. ], 6.v.1908, 1 J ( ZMHB, ex coll. O. Duda); Puszczykowskie Góry, XT29, 8.v.2008, 1 J 1 ♀, in copula, leg. P. Trzciński ( PTPP); Trzcielińskie Bagno, XT19, 1.–10.v.2008, 2 JJ, Moericke trap, leg. P.Trzciński ( RZRP);Trzcielińskie Bagno, 24.iv.2010, 3 JJ, leg. P. Trzciński ( PTPP); Jarosławiec, XT29, 19.v.2011, 1 J, leg. P. Trzciński ( PTPP); Kartoszyno, CF16 (all leg. RZ), 30.v.2021, on Apiaceae near the stream, 1 J ( Figs 2A , 3A ) ( MZPW), 3.vi.2021, 2 JJ on Crataegus sp. ( RZRP), 3.vi.2021, 1 J on Crataegus sp. ( ZFMK), 5.vi.2021, 3 JJ 1 ♀ on Crataegus sp. ( RZRP), 22.v.2022, 2 ♀♀ (GenBank acc. no. OR859735, OR859692), in riparian forest near the stream ( RZRP), 27.v.2022, 2 JJ (GenBank acc. no. OR859707, OR859656) on Crataegus sp. ( RZRP), 4.vi.2022, 1 J caught “in copula” with allotype and deposited in ZMHB, 4.vi.2022, 2 JJ 2 ♀♀ on Crataegus sp. , leg.RZ ( RZRP), 1 J 1 ♀ on Crataegus sp. ( ZFMK), 28.v.2023, 4 JJ (GenBank acc. no. OR859675, OR859668, OR859677), 1 ♀ (GenBank acc. no. OR859730) on Crataegus sp. ( RZRP), 29.v.2023, 3 JJ (GenBank acc. no. OR859712) on Crataegus sp. ( RZRP), 3.vi.2023, 2 ♀♀ (GenBank acc. no. OR859695, OR859679) in riparian forest ( RZRP); Stawiska ad. Miękinia, CA 95, 10.iv.–5.v.2022, 2 JJ, Malaise trap, leg.Ł. Mielczarek ( LMMP); Słowiński National Park, O.O. Smołdzino, distr. 129 (old railway embankment), 16.v.2022, 1 J, on Pyrus sp. , leg. RZ ( RZRP); Żegocin, marshy alder forest,XT96, 30.iv.2023, 1 J, leg. P.Żurawlew ( RZRP). SERBIA: Tara, Manastir Rača, 43.9166667N 19.535E, 28.iv.2012, 1 J, leg. Vujić A., Radenković S., Likov L. ( FSUNS). SPAIN: Cortes de la Frontera, 15.iv.2023, 1 ♀, leg. FM ( FMTB); Capileira, 17.iv.2023, 1 J, leg. FM ( FMTB); Lugros, rio Alhama, 19.iv.2023, 1 J (GenBank acc.no. PP214180) ( Fig. 7D ), leg. FM ( FMTB); Sierra Nevada, vic.of Monachil, 1650 m a.s.l., near forest stream in Pinus -Quercus mountain belt, 37.13N 3.44W, 1 J, 24.iv.2023, leg. Popov G. ( SIZK).

Additional material studied. 70 JJ 24 ♀♀. BELGIUM: Bonheiden, Dorstveld, 8.v.1999, 1 ♀, leg. FM ( FMTB); Diepenbeek, De Maten 8, 29.v.2002, 1 ♀, leg. FM ( FMTB); Tessenderlo, Engsbergen,Achterheide, 1.v.2011, 1 ♀, leg. FM ( FMTB);Assent, Papenbroek, 5.–19.iv.2012, 1 J, Malaise trap, leg. FM ( FMTB); Holsbeek,Dunbergbroek, 2.v.–2.vi.2012, 2 ♀♀, Malaise trap, leg. FM ( FMTB); Torgny, Réserve Naturelle Raymond Mayné, 10.iv.2015, 1 ♀, leg. FM ( FMTB); Ovifat, Reinhardstein, 5.vi.2015, 1 ♀, leg. FM ( FMTB); Oudenaarde, Bos t’Ename, 6.v.2015, 2 ♀♀, leg. FM ( FMTB); Meeuwen-Gruitrode, Itterbeek Eetsevelderbeek, 4.v.2016, 1 ♀, leg. FM ( FMTB); Lavacherie, Rue St. Ode, 30.iv.2017, 1 ♀, leg. FM ( FMTB); Awenne, Rue de Souvenir, 10.v.2017, 1 ♀, leg. FM ( FMTB); Champlon, Barrière de Champlon, 25.v.2017, 1 J, leg. FM ( FMTB); Léglise, 24.iv.2021, 1 ♀, leg. FM ( FMTB); Rossignol, Rue de Hageai, 24.iv.2021, 1 J (GenBank acc. no. OR859705), leg. FM ( FMTB). CZECH REPUBLIC: Bílý Potok, nature reserve Nad koupalištěm, 430 m, wetland, 22.v.2003, 1 J, leg.J.Preisler ( LMJC) (MAZÁNFK et al.2009, as O. brevicornis ); Mníšek u Liberce env., 400 m, meadow, 24.v.2003, 3 JJ, leg. J. Preisler ( LMJC) (MAZÁNFK et al. 2009, as O. brevicornis ); Jizerské hory Mts, Nature reserve Meandry Smědé, pond Dubák env., wetland, alder, Malaise trap, 19.v.–31.v.2005, 3 JJ 3♀♀, leg.J. Preisler & P. Vonička ( LMJC) (MAZÁNFK et al. 2009, as O. brevicornis ); Jívová, u Dómského lesa, 540 m, on flowering Crataegus sp. , 27.v.2017, 4 ♀♀, leg. L. Mazánek (2 ♀♀ LMJC, 2 ♀♀ RZRP), 28.v.2017, 3 ♀♀, leg. L. Mazánek ( LMJC). Sedm Dvorů, Bystřice valley, 510 m, sweeping on flowering Salix sp. , 10.v.2021, 1 J, leg.L.Mazánek ( LMJC); Krkonošský NP, Vítkovice, 650 m, on flowering Crataegus sp. , 8.vi.2022, 1 J, leg. L.Mazánek ( LMJC). DENMARK: Langaa, Dania: EJN, 2.vi.1987, 1 J, leg.J.A.W. Lucas ( RMNH). FRANCE: Savigny, la Prairie, 23.iv.2010, 1 J, leg.X. Lair ( XLSF); Ducey-les-Chéris, Bois d’Ardennes, 15.v.2008, 1 J, leg. X.Lair ( XLSF). GERMANY: Langballigau, Schleswig-Holstein / Nordangeln, 6.v.1972, 1 J, leg. C. Claussen ( ZFMK); Langballigau, 8.vi.1976, 1 J, 10.vi.1976, 3 JJ, leg. C. Claussen ( ZFMK); 25 km S Oldenburg, Ahlornerteiche, 10.v.1980, 1 J, W. Barkemeyer ( ZFMK); Langballigautal, Schleswig-Holstein /E of Flensburg, 14.v.1983, 1 J, leg. J.A.W. Lucas ( ZFMK); Flensburg, Schleswig-Holstein, Roikier See, 21.vi.1987, 1 J, 22.vi.1987, 2 JJ, leg. J.A.W. Lucas ( ZFMK); LK Uelzen, Grosses Bruch bei Altenebstorf, 22.v.1991, 3 JJ, 17.vi.1991, 1 J, 6.v.1995, 2 JJ, 25.v.1997, 3 JJ, 7.v.1998, 2 JJ, leg. D. Wolff ( ZFMK); LK Uelzen, Galgenberg bei Grünhagen, Nordhang Quelliger Laubmischwald, 29.v.1991, 1 J, v.1997, 1 J, leg. D. Wolff ( ZFMK); LK Uelzen, Niehof bei Veersen Erlen-Eschenwald, 18.v.1992, 4 JJ, leg. D. Wolff ( ZFMK); Insmühlen Umgebung, Lüneburger Heide, 7.v.1994, 2 JJ, 10.v.1994, 4 JJ, leg. J.-H. Stuke ( ZFMK); LK Uelzen, im Sieken bei Westerweyhe quelliger Erlenwald, 12.v.1994, 1 J, leg. D. Wolff ( ZFMK); Darmstadt, Messel Buchenwald, 2.v.1995, 1 J, leg. M. Hauser ( ZFMK); LK Uelzen, Eitzener Bruch bei Eitzen, 9.v.1998, 1 J, leg. D. Wolff ( ZFMK); LK Stade, Surbrook b.Fredenbeck, 14.v.1998, 3 JJ, leg. D. Wolff ( ZFMK); Zorge, Neue Teich near Zorge, Harz, Niedersachsen, 18.v.2002, 1 J, leg.W. van Steenis ( WSBN); Harz-Südrand, Hirseteich, 1 km NW Walkenried, 19.v.2002, 5 JJ, leg. J.-H. Stuke ( ZFMK); Harz-Südrand, Oberaue zwischen Breitenbach und Unterzorge, 31.v.2003, 1 J, leg. J.-H. Stuke ( ZFMK); Markhausen, Niedersachsen, Emsland, Markatal SW Markhausen, 1.v.2005, 1 J, leg. J.-H. Stuke ( ZFMK). POLAND: Żegocin, marshy alder forest, XT96, 7.v.2023, 1 ♀, leg. P. Żurawlew ( RZRP). SWITZERLAND: Chevroux, 8.–15.v.2020 (Malaise trap), 1 J, leg. Association de la Grande Cariçaie, Nina Perret-Gentil ( MZLS). UNITED KINGDOM: Sutton, Sutton Park, 18.v.1997, 1 J, leg. S. Falk ( SFKU); Lewes, Mount Caburn, 17.iv.2005, 1 J, leg. S. Falk ( SFKU); Birdford-on-Avon, Marsh Farm, 14.vi.2014, 1 J, leg. S. Falk ( SFKU); Hampshire, Ashford Hangers, 30.v.1987, 1 J, leg. R. B. Hastings ( RMMU);West Norfolk,East Walton Common SSSI, 18.v.2007, 1 J, 19.v.2007, 1 J, leg. R. Morris ( RMMU); East Suffolk, Walberswick, 2.v.1990, 1 J, leg. R. Morris ( RMMU).

Diagnosis. A black Orthonevra ( Figs 1A–B ) with metallic reflections, completely black legs, shiny sternite I and suboval postpedicel (1.1–1.25 times as long as wide, sometimes slightly angular at tip regardless of sex) and largely black with orange-brown basoventral area. Males of O. atlantica sp. nov. are best distinguished from other Orthonevra by morphological characters of the terminalia. The characteristic shape of the surstylus, wide in the basal half of its length, then abruptly narrowing into a curved tip ( Fig. 5A ), is a diagnostic character shared only with two other west Palaearctic species: O. brevicornis and the North-African endemic of the high Atlas O. bouazzai Kassebeer, 1999 . Males of O. atlantica sp. nov. are easily distinguishable from these two species by further characters of the terminalia: O. brevicornis has several significant differences in the shape of the phallus, the postgonites and the posteroventral process of the surstylus (for details see species descriptions and compare Figs 4A and 5A–C with Figs 4B and 5D–F ). Orthonevra bouazzai differs from O. atlantica sp. nov. in the shape of the postgonites with a slender anterodorsal tip and three denticles on its posterodorsal margin ( Figs 10 –11 in KAssFBFFR 1999). Males of O. atlantica sp. nov. are also distinguishable by non- -genital characters: from O. brevicornis mainly by having black hairs on the scutum and on the vertex (yellow in O. brevicornis ) and from O. bouazzai (both sexes) by having a shorter and partly orange-brown postpedicel (elongated and black in O. bouazzai ). Females of O. atlantica sp. nov. have an unmodified tergite V without a keel or incision, a shiny sternite I and a partly orange short postpedicel — a set of characters that differentiates them from the females of all other European Orthonevra species except for the females of O. brevicornis . Characters to distinguish females of O. atlantica sp. nov. and O. brevicornis are subtle and influenced by individual variability. The colour of the postpedicel of O. atlantica sp. nov. is black with a restricted orange-brown area basoventrally, whereas the orange-brown area extends more to the tip in O. brevicornis with the dark areas often being brown instead of black. A subtle but generally good indicative feature is found in the wing venation: if we draw an imaginary line between the vein junctions M 1 /M 2 and C/R 2+3, the junction M 1 /R 4+5 is located usually at the wing base side of this line in O. atlantica sp. nov. ( Figs 7A, 7B ), whilst in O. brevicornis it is usually situated on the line or at the wing tip side ( Figs 7F, 7G ). It is worth noting that similar characteristic was proposed to distinguish between O. arcana Ricarte & Nedeljković, 2022 and O. incisa by RlCARTF et al. (2022). In addition, O. atlantica sp. nov. is on average sturdier than O. brevicornis and has a slightly wider face (but face width is rather variable), the body hue is (especially in fresh specimens) pitch black to dark olive green in O. atlantica sp. nov., whereas the colour of O. brevicornis is more dark grey to grey-blue. The colour of the wing venation is on average darker in O. atlantica sp. nov. All the above indicative characters of females also apply to males. Females of one species belonging to another genus, Lejogaster metallina (Fabricius, 1777) , have been found originally partially misidentified as O. brevicornis in one of the very old collections (ŻÓRALsKl 2023), so they can also be confused with females of O. atlantica sp. nov. Despite similar overall appearance, the wing vein M 1 in the females of L. metallina is, however, processive (non-recessive) and their mouthparts are strongly protruding.

Description. Male. Body length 5.6–7.0 mm (n = 34; average = 6.3 mm; median = 6.5 mm; holotype = 6.5 mm), black with metallic reflections ( Fig. 1A ).

Head. Eyes bare. Antennae ( Fig. 3A ): scape black; pedicel black with a few white hairs ventrally that are as long as segment width and with a few shorter black hairs dorsally; postpedicel slightly longer than wide (length to width ratio 1.1–1.25×), slightly angular at tip, bicoloured: overall black but with orange-brown area ventrally near its base. Sensory pit present on outer side. Arista black, twice as long as postpedicel. Face ( Fig. 2A ) broad (holotype: upper face width 0.95 mm; lower face width 1.25 mm), slightly wider than half width of head, shiny black, with diverging eye margins. Upper and lateral part of face with wrinkled texture, central part above mouth protrusion with smooth, bare surface. All facial hairs white to yellow, covering part of face, largely missing in central area. Central symmetrical trapezium-shaped area of white pilosity just below antennal sockets connected to triangular areas of white pilosity near eyes. Facial hairs shorter near mouth. Face below antennal sockets in profile ( Fig. 2B ) almost straight but varies between individuals from completely straight to slightly convex. Mouth edge in profile protruding far beyond antennal sockets, covered with yellowish to light brown hairs. Frons prominent, shiny, punctuated, covered with yellowish hairs with some hairs in middle black. Vertex shiny, punctuated, with long black-brown hairs bent forward. Ocelli forming equilateral triangle. Occiput with band of white pilosity along eyes.

Thorax. Scutum black with metallic, densely punctuated cover. Covered with short erect hairs of equal length, with a few longer hairs. Majority of hairs on scutum black (best seen in posterior view), exceptionally (two specimens from Belgium) all white. Four darker, gold-brown shiny, longitudinal vittae appear where this cover has less dense or absent punctation. Scutellum metallic black, covered with yellowish hairs, with rim along posterior margin and with row of hairs at margin, some slightly bent towards midline, shorter than half length of scutellum. Anterior anepisternum shiny, without hairs, except for very short hairs on its posterior dorsal part. Posterior anepisternum shiny, covered with long hairs, except for its bare anteroventral part. Hair patches on upper and lower katepisternum widely separated.

Wings transparent but slightly darkened and completely covered with microtrichia. Venation black. Vein M 1 bent in middle, recessive through location of junction M 1 /R 4+ 5 in wing topology towards wing base, as illustrated on Fig. 7A ; varying between individuals as on Figs 7C–E . Pterostigma light brown with dark brown basal area. Halteres yellow-grey.

Legs. All legs shiny metallic black. Femora slightly swollen, two times maximum width of tibia. Tibia covered with short adpressed white hairs, fore and mid femora covered with upstanding longer whitish hairs on posterior side, longest hairs on posteroventral side, some more than 3/4 of femora width. Hind femora with short hairs, less than half femur width. Ventral side of hind femora covered with short adpressed black bristles. Ventral side of all tarsomeres of middle legs covered with short adpressed black bristles. First tarsomeres of middle legs with four longitudinal rows of these bristles, inner rows located close to each other. Middle tibiae with some black bristles at top. Claws orange at base, black at tip.

Abdomen oval, black. Dull and lightly pollinose in central areas, shiny olive-golden metallic on sides of all tergites. Dull area on tergite IV forms triangular (rarely slightly trapezoid), backwards directed vitta, covering around 50% of tergite. Shiny parts of tergites covered with white adpressed hair, directed towards sides of tergites. Dull central area covered with shorter and much sparser hairs. Sternites covered with white hairs: sternite I shiny with sparse hairs restricted to median part; sternite II with erect and long hairs; sternites III and IV with shorter and inclined hairs, pointing backwards or to centre of sternite.

Terminalia. Surstylus very wide in basal half with broadest section in middle part and with top abruptly narrowing into curved tip ( Figs 5A–C ). Posteroventral process of surstyli rudimentary ( Fig. 5B ). Phallus, in anterior view ( Fig. 5C ), shaped as broad cylindrical, concave cavity. In lateral view ( Fig. 5A ), with rather long, slender anterodorsal hook-shaped appendix and small anteroventral appendix. Beneath these third delicate, long, recurving, bristle-like process of phallus, extending far outside genital capsule from beyond anteroventral edge of postgonites. Postgonites with quadrate tip posterodorsally, extending beyond tip of phallus. Each postgonite with small denticle on its anterior edge and with single strong seta beneath. Hook-shaped anteroventral extension of postgonite, found in O. brevicornis , is missing ( Fig. 5B ).

Female. Body length 5.9–7.0 mm (n = 12; average = 6.6 mm; median = 6.6 mm). Resembling male ( Fig. 1B ) except for the following: eyes dichoptic; frons with five (sometime six) deep and distinct lateral furrows, abdomen broader, face in lateral view more concave, hairs on scutum all white to light brown (no black hairs) and hairs on vertex pale (single black might appear). Tergite V with shallowly curved posterior margin and without keel or incision in middle. The same variability in wing topology and postpedicel length to width ratio as reported for males. Biology and behaviour. Males of this species have been observed sitting next to water-filled tracks in deciduous forest with wood and leaf debris and along the muddy margins of small forest streams. Most individuals from Poland (locus typicus) were caught on a solitary hawthorn shrub close to a spring-fed marshy area with alder carr and in direct vicinity of small streams with clean and cold water. Elsewhere, this species is found mostly close to small and shaded rivulets in deciduous forest, or in deciduous forests with seepages. In Southern Europe it becomes increasingly montane (up to 1720 m a.s.l.), though less so in areas with high rainfall.

Etymology. From the Latin atlanticus, meaning “of or near the Atlantic Ocean”, referring to the main compact biogeographical region of occurrence of this species in Europe, as opposed to the similar O. brevicornis that is nearly absent in these areas.

Distribution. Species with a mainly Atlantic distribution ( Fig. 8 ) with its strongholds along the Central European Atlantic coast and in Great Britain, extending east to the Baltic coast and south-west parts of Poland, and south into the Iberian Peninsula. Scarcer and more isolated records appear out of the Atlantic zone. The range of O. atlantica sp. nov. is very similar to the range of two other Brachyopini species, i.e., Melanogaster hirtella ( Loew, 1843) and Chrysogaster virescens Loew, 1854 , also explicitly referred to or presented as “Atlantic” species (SPFlGHT 2017).

Molecular data. A total of 16 specimens of O. atlantica sp. nov. from Belgium, Poland and Spain were successfully sequenced for this study. Additionally, we downloaded another sequence from BOLD and two more sequences from GBOL belonging to specimens previously identified as O. brevicornis coming from England and Germany, respectively. In our NJ tree we recover all sequences of O. atlantica sp. nov. and O. brevicornis together, forming a cluster with high support (BS = 100%).All sequences of our new species cluster together with high support (BS = 100%), except for one Belgian specimen (GenBank accession number OR859705) and a Spanish individual (PP214180) ( Fig. 10 ). The COI sequences of O. atlantica sp. nov. show an uncorrected intraspecific pairwise distance between 0.0 and 0.014 (or a difference between 0.0 and 1.4%).

External and genital morphology of the Belgian male from Rossignol (GenBank acc. no. OR859705) was carefully studied several times and by different people (FM and XM), and we confirm that it belongs to O. atlantica sp. nov.. The terminalia are still attached to the male body (they were extended and rotated, but not detached), assuring that terminalia were not swapped with other individuals. We, thus, exclude the possibility of a morphological misidentification of this individual. During the molecular laboratory steps, in the 96-well plate where this specimen was included, all its neighbour wells contained either other genera or species, or individuals of O. atlantica sp. nov. This makes a material switch between a specimen of O. brevicornis into the well corresponding to the Belgian male very unlikely. We are confident that there was no error made in the laboratory. A second attempt to re-sequence this Belgian fly failed. The fact that this specimen shares the COI haplotype with another individual of O. brevicornis was not expected, as the differences in external morphology and genitalia are clear and stable, but it is not uncommon in Syrphidae that two different species share the same COI haplotype (see Discussion). Moreover, the placement of the Spanish specimen of O. atlantica sp. nov. from Lugros (GenBank acc. no. PP214180) in the NJ tree between the two clusters of O. atlantica sp. nov. and O. brevicornis (without high support value), whereas it agrees morphologically completely with the concept of O. atlantica sp. nov., and the low interspecific variability between these two species reinforces the results from our study, so we can conclude that both species cannot be unmistakably characterised using DNA barcodes.

Figures

Fig. 1. Overall appearance, lateral view.A – Orthonevra atlantica sp. nov., male, holotype; B – O. atlantica sp. nov., female, paratype; C – O. brevicornis (Loew, 1843), male, neotype; D – O. brevicornis, female.

Fig. 2. Male, head, anterior and lateral view. A – Orthonevra atlantica sp. nov., paratype; B – O. atlantica sp. nov., holotype; C, D – O. brevicornis (Loew, 1843), neotype.

Fig. 3. Postpedicel coloration. A – Orthonevra atlantica sp. nov., male, paratype; B – O. brevicornis (Loew, 1843), male, neotype.

Fig. 4. Male terminalia, lateral view. A – Orthonevra atlantica sp. nov., holotype; B – O. brevicornis (Loew, 1843), neotype.

Fig. 5. Male terminalia. A, B, C – Orthonevra atlantica sp. nov., holotype, Poland, Kartoszyno; D, E, F – O. brevicornis (Loew, 1843), Poland, Jeleń.

Fig. 7. Variation in the shape of the M1 vein of the wing. A–E – Orthonevra atlantica sp. nov.: A – J, holotype, Poland, Kartoszyno; B – ♀, paratype (allotype), Poland, Kartoszyno; C – J, paratype, Poland, Kartoszyno; D – J, paratype, Spain; E – J, paratype, Belgium. F–J – Orthonevra brevicornis (Loew, 1843): F – J, neotype, Poland, Poznań vicinity; G – ♀, voucher specimen, Poland, Poznań vicinity; H – J, Germany, Frankfurt am Main; I – J, Poland, Jeleń; J – J, Georgia, Dviri.

Fig. 10. Neighbour-Joining tree of a 573 bp alignment of the mitochondrial cytochrome c oxidase subunit I gene (COI). The numbers above the branches are bootstrap values>80% based on 1000 replicates. For each sequence and separated by a |, the name of the species, the GenBank accession number and the country of origin of the specimen are given.

Fig. 8. Verified distribution of Orthonevra atlantica sp. nov. and O. brevicornis (Loew, 1843).