Gymnocheta magna Zimin, 1958

Pohjoismaeki, Jaakko & Bergstroem, Christer, 2021, Review of the Nordic Gymnocheta Robineau-Desvoidy (Diptera, Tachinidae) with report of two species new to Europe, ZooKeys 1053, pp. 145-184 : 145

Gymnocheta magna Zimin

Gymnocheta magna Zimin, 1958: 53. Lectotype ♂ [ZIN], by designation of Richter (1981: 917) (see below).

Material.

Russia: Lectotype ♂, by designation of Richter (1981: 917). Type locality: Ущ. Суцэуктз, ю.-а. Кентей, Монголия, конец V. 1924 ( Козлов). Mongolia, Hentiy Aimag [as “Kentei” in Russian], Sutszukte. Not examined. Sweden: (4♂♂, 6♀♀) 1♀: SE, UP, Årsta / Slavsta, O 1606484 N6639427, 16.vi.1980, leg. C. Bergström [CBC]; 2♀♀: SE, UP, Kvarnbo, O 1598600 N6637685, 6.vi.1982, leg. C. Bergström [CBC]; 1♀: SE, UP, Ekebydalen, O 1600268 N6637514, 6.vii.1983, leg. C. Bergström [CBC]; 1♂: SE, UP, Skogsängen, Nåsten, O 6636152 N1597099, 11.vi.1986, leg. C. Bergström [CBC]; 2♂♂, 1♀: SE, UP, Skogsängen, Nåsten, O 6636152 N1597099, 22.vi.1987, leg. C. Bergström [CBC]; 1♀: SE, UP, Skogsängen, Nåsten, O 6636152 N1597099, 27.vi.1987, leg. C. Bergström [CBC]. Finland: (2♂♂, 3♀♀) 1♂: Ostrobottnia media, Raahe, Hakotauri, 64.7002; 24.4736, 3.vii.2006, K. Varpenius leg. (BOLD Sample-ID JP00229, GenBank accession number KX844302 ) [TMNH]- 1♂: Finland, Karelia borealis, Ilomantsi, Ilajansuo, 62.915455; 31.201721, 20.vi.2013, J. Pohjoismäki leg. [JPC]; 1♀: Ostrobottnia kajanensis, Kuhmo, Ulvinsalo, 63.973506; 30.319950, 22.vi.2019, J. Pohjoismäki leg. [JPC]; 1♀: Regio Aboensis, Mietoinen, Perkko, 6733:3222, 9.v.-16.vi.2004, A. Haarto leg. [AHC]; 1♀: Tavastia australis: Pälkäne, 6807:3353, 27.vi.1993, Y. Ranta leg. [AHC]. Japan: (2♂♂, 1♀) 1♂: [KYUSHU] / Takachiho-mine / Kagoshima pref. // VI-7-1960 / H. Shima leg. (handwritten) // Gymnochaetopsis / magna Zimin / det. H. Shima 2020 [BLKU]; 1♂: [KYUSHU] / Mt. Takachiho / Kagoshima // 16.vi.1968 / A. Nakanishi (handwritten) // Gymnochaetopsis / magna Zimin / det. H. Shima 2020 [BLKU]; 1 ♀: [HONSHU] / Niigata / Myôkôkgen-sho / Sasagamine / 22.vi.1996 / T. Tachi [BLKU].

Diagnosis. A lucid green Gymnocheta species with a notably protruding lower facial margin and green femora. This is also the only European Gymnocheta species with short costal spines.

Redescription

[values in brackets refer to the holotype of T. viridis Fallén]. Body length: 7.8-12.1 [12.1] mm (n = 10).

Male (Figs 1B-E , 2B , 4Eii, 5A:ii, B:ii, C:ii).

Colouration: Head covered with a greyish white microtomentum. The metallic ground colour subshiny on the genal dilation but the shine/intensity is depending on the direction of the incident light. Facial plate with a greyish white microtomentum; lower protruding area however with a distinct mint metallic green tint. Occiput, postgena, genal dilation, ocellar tubercle metallic green in ground colour. Fronto-orbital plate narrowly but mostly distinctive mint metallic green along the frontal row of setae. Palpus, clypeus (sometimes with a metallic green tint) and prementum dark brown to black, labella brown beige. Thorax and abdomen bright mint metallic green in ground colour, contrasting with gilt or purple lustre depending on the direction of the incident light, with an indistinct greyish white microtomentum. Scutum when viewed from the side and slightly from behind with four longitudinal stipes changing from grey to gilt or purple depending on the direction of the incident light. Proepisternum normally with the metallic green ground colour subshiny, but less so in dwarfish specimens. Fore coxa in anterior region and femur posteriorly mostly with a metallic green shine. Wing membrane around crossvein r-m rarely infuscated. Tegula and basicosta dark brown or black.

Head (Figs 1C , 2B ): Frons narrower than in G. lucida , at its narrowest point 0.31-0.38 [0.37] (n = 6) × as wide as an eye in dorsal view. Frontal vitta gradually tapering toward ocellar tubercle. Frons in lateral view somewhat protruding, width of parafacial at level of antennal insertion 0.59-0.72 [0.72] × (n = 6) the horizontal eye diameter. Fronto-orbital plate with a row of 10-14 [11] medioclinate frontal setae, mixed with some setulae, three to five setae descending on upper part of parafacial, reaching the middle of the pedicel with the row curving laterally, uppermost tiny setulae sometimes reclinate; orbital plate at level of ocellar tubercle with numerous moderately long and tiny setulae, frontal plate with more sparsely spread short and tiny setulae. Height of face 0.79-0.85 [0.80] × the length of frons (n = 6). Gena in profile at narrowest point, 0.35-0.39 [0.38] (n = 6) × as high as vertical eye diameter. Facial plate bulged medially and slightly visible in lateral view, lower facial margin distinctly protruding, in strict lateral view visible in front and below the vibrissa. Facial ridge on lower 0.20-0.25 with 1-3 [2] strong and 0-3 [2] additional thinner supravibrissal setae (length of them at least subequal to narrowest width of parafacial) and 2-5 thin and short setulae. Below the vibrissa 4-7 [7] strong subvibrissal setae continuous in front of the genal setae, the posteriormost subvibrissal seta close to the foremost lower genal margin. Inner vertical setae crossed, thin and weaker or at most subequal in length with the ocellar setae, outer vertical setae at most subequal with the adjacent postocular setae. Postocular setae long and thin, apically pronouncedly bending forward over the eyes. Occiput and postgena both with white to greyish white hairs. Antennae: First flagellomere in profile 0.90-1.06 (n = 5) × the actual width of parafacial; at narrowest point; 1.52-1.79 (n = 5) as long as than pedicel. Arista widened in its proximal ¼ -1/3, gradually tapering towards apex.

Thorax (Fig. 1B ): Prosternum frequently with tiny setulae [without]. Scutum with 3(4)+3 [3+3] acrostichal, 3-4 dorsocentral and 1+3 intra-alar setae. Scutellum with 4(5) [5] pairs of strong setae along margin, apical and subapical pairs slightly diverging; 2-4 [3] suberect dorsal scutellar setae, in front of the subapical setae, the strongest subequal to the lateral setae, rarely with an additional pair of medium strong median dorsal setae; tiny dorsal setulae numerous, the longest at least 1/2 length of the strongest dorsal seta.

Legs: Claws and pulvilli on fore legs slightly longer than fifth tarsal segment, the latter 1.7-2.0 (n = 3) × as long as the fourth. Fore tibia with a row of 5-6 anterodorsal setae, and an irregular row of 2-4 posterodorsal and 2 posterior setae; preapical anterodorsal seta subequal with the preapical dorsal seta, preapical posterodorsal seta short, its length rarely exceeding 1/3 of the dorsal seta. Mid tibia with three or four anterodorsal setae, the strongest in the middle of row, five or six posterior (pd and p) setae, one ventral seta often accompanied by an additional tiny setula. Hind tibia with a continuous row of nine or ten unequally strong anterodorsal setae / setulae of which four or five represent strong setae, three or four posterodorsal setae, the lowest one the strongest, and two or three anteroventral setae.

Wing: (Fig. 1B , 1D ) Usually two costal spines, both short and the strongest ventral spine at most 1.5 × as long as the strongest surrounding costal setulae, normally only slightly exceeding 1/2 the length of crossvein r-m. CS4 + CS5 2.0-2.3 (n = 3) × as long as CS6. Vein R4+5 at base with 2-4 ventral and 3-5 dorsal setulae.

Abdomen (Fig. 1B ): Tergite 2 without a pair of median marginal setae, with 1(2) lateral marginal setae on each side. Tergites 3 and 4 with two or three unequally strong and often irregularly set pairs of median discal setae (sometimes two pairs and one unmatched seta). Tergite 3 with a pair of medial marginal setae, tergite 4 in dorsal view with a full row of 10-12 [10] marginal setae, tergite 5 with two or three irregular rows of strong and medium strong discal setae and a dense row of weak marginal setae.

Terminalia (two dissections) (Figs 1E , 4Eii, 5A:ii, B:ii, C:ii): Sternite 5 (Figs 1E , 4Eii) in ventral view with short and wide lobes; length of cleft 1.7-1.8 × its maximal width. Lobes with widespread tiny setulae, curved inward at apex (posteriormost region in ventral and slightly lateral view with a subtriangular appearance); Dorsomedial process black and expanding backwards, strong, and very characteristic in part separated from sternite 5. Basal plate bare (without setulae) ca. 0.45 × as long as sternite 5 and 2.2-2.3 × as wide as long. Syncercus in lateral view (Fig. 5A :ii) smoothly curved at apex, similar to G. lucida ; in caudal view (Fig. 5B :ii) somewhat resembling a pointed triangle with long basal lobes; 1.7-1.8 × as long as its maximal width (measured from base of membranous median suture to apex), slightly incurved at middle and close to a characteristic wide and blunt apex, dorsolateral at middle with numerous relatively long setulae. Surstylus (Fig. 5A :ii) slender, straight in caudal view; in lateral view slightly arch-like bent at ca. middle, almost evenly thick apart from apex that is slightly widening, bent towards syncercus. Pregonite lobe-like in lateral view with a wide hook-like projection, with short sensorial hairs along its proximal posterior margin, anterior margin slightly more curved than in G. lucida . Aedeagus: Distiphallus (Fig. 5C :ii) in lateral view compact but not widening close to apex.

Female (Figs 3B , 6A :ii, B:ii): Differs from male as follows:

Colouration: Fronto-orbital plate vivid mint metallic green when viewed from behind and slightly from above; the metallic ground colour continues down on the upper part of parafacial reaching the level of the lowermost frontal setae; the upper part of parafacial and anterior 1/3 of fronto-orbital plate with a thin greyish white microtomentum, visible along eye margin and as a slim line at the edge of frontal vitta. Thorax and abdomen vivid metallic green, at most with thin whitish microtomentum.

Head (Fig. 3B ): Frons wider, at its narrowest point 0.75-0.83 (n = 5) × as wide as an eye in dorsal view. Frontal vitta gradually tapering towards ocellar tubercle, at this level often narrower than width of fronto-orbital plate. Fronto-orbital plate normally with fewer, 8-11 moderately strong medioclinate frontal setae. Outer vertical setae fairly stronger than the ocellar setae, shorter than the posteriormost proclinate orbital setae, at least twice the length of the adjacent postocular setae. Postocellar setae short and tiny and subequal with the upper postocular setae. One female with a long and slender first flagellomere otherwise not deviating from the situation in males 1.55-1.88) (n = 5) × as long as pedicel; its maximum width 0.94-1.08 (n = 5) × the actual width of parafacial at narrowest point.

Legs: Claws and pulvilli on fore legs shorter ca. 0.7-0.8 × as long as tarsal segment 5, the latter 1.5-1.7 × as long as tarsal segment 4.

Abdomen: Ground vestiture dorsolateral on tergites 3 and 4 distinctly prone contrasting to the erected setulae between the median discal setae. Tergites 3 and 4 normally with two or three pairs of median discal setae, tergites 3 and 4 occasionally devoid of one seta. Sternite 5 (Fig. 6A :ii) somewhat elongated, 1.1-1.2 × as long as its maximal width, with four strong setae along posterior margin accompanied by numerous irregularly spread setulae of varying size and one to two additional strong seta in posterior 4/5.

Terminalia: (two dissections) (Fig. 6B :ii)Tergite 6 divided into narrow and somewhat elongated hemitergites, widely separated, each in the membranous area accompanied by 3 tiny setulae posterior to the seventh spiracle and one or two setulae in a more apical position. Sternite 6 shorter, 0.5-0.6 × as long as but slightly wider (1.2 ×) than sternite 5, 2 × as wide as long with four setulae along the posterior margin and with numerous tiny setulae in posterior 1/5. Tergite 7 with three setulae in the adjacent membranous area close to lingulae. Sternite 8 strongly reduced, hidden between hypoproct and sternite 7; compared with G. lucida and G. viridis rather well developed; possesses at least 20 sensorial pores of which some are provided with tiny setulae; laterally on both sides with a long setula. Hypoproct (Fig. 6B :ii) in ventral view semicircle-shaped, with a distinct middorsal depression, densely covered with setulae, laterally on both sides with one longer setula, in lateral view not bent towards the cerci, apex of hypoproct reaching tip of cerci, lingulae well developed. Epiproct strongly reduced (no sclerotising visible) but in caudal view indicated by the presence of up to ten setulae inserted above the cerci. Cerci with numerous setulae of varying length, in lateral view the strongest setulae are at least subequal in length with sternite 7.

DNA.

Gymnocheta magna has a unique Co1 barcode sequence, BOLD:ACA9848 (Fig. 7 ).

Distribution.

Widely distributed in the Palaearctic Region ( O´Hara et al. 2009). Gymnocheta magna is a relatively rare but widespread species in northern Europe. It was recorded as new to Sweden in Hedström (1985) and to Norway in Haraldseide (2012). It was listed from Finland in the checklist by Hackman (1980). The oldest specimen in MZH is from 1865, from Finland.

Biology.

The biology of Gymnocheta magna is poorly known. This is a summer species in the Nordic countries with a flight time from early June to mid-July. It is not a heathland specialist as suggested by some sparse records from Central Europe ( Tschorsnig and Herting 1994), but has also been caught from meadows, forest margins and gardens (see also Fallén’s notes below). Both sexes visit flowers, especially those of cow parsnip, Anthriscus sylvestris (L.) and caraway, Carum carvi L. Females have been observed basking on aspen leaves. Hosts are unknown but are likely to be concealed larvae of Erebidae ( Lepidoptera ); see G. viridis .

Figures

Figure 1. Gymnocheta spp. habitus A habitus Gymnocheta viridis ♂ B-E Tachina viridis Fallen, holotype specimen B dorsal view C head in lateral view. Note the protruding lower facial margin (arrowhead) D detail of the right wing edge. Note the reduced costal spine (arrowhead) E sternite 5 of the holotype F labels associated with the holotype. All photographs by Goeran Liljeberg.

Figure 2. Gymnocheta spp. male heads in lateral (upper panels) and dorsal (lower panels) view A Gymnocheta lucida Zimin B G. magna Zimin C G. viridis (Fallen) D G. zhelochovtsevi Zimin. Note the wide frons and strong outer vertical bristles. Scale bars: 1 mm. All photographs by Goeran Liljeberg.

Figure 3. Gymnocheta spp. female heads in lateral (upper panels) and dorsal (lower panels) view A Gymnocheta lucida Zimin B G. magna Zimin C G. viridis (Fallen) D G. zhelochovtsevi Zimin. Scale bars: 1 mm. All photographs by Goeran Liljeberg.

Figure 5. Comparison of Gymnocheta spp. male terminalia A lateral view of the terminalia: i G. lucida ii G. magna iii G. viridis and iv G. zhelochovtsevi - note the apical hook of the syncercus B dorsal view of the terminalia: i G. lucida ii G. magna iii G. viridis and iv G. zhelochovtsevi, same specimen as in Fig. 4 C C aedeagus and gonites of i G. lucida ii G. magna iii G. viridis and iv G. zhelochovtsevi. Abbreviations: bph - basiphallus; dph - distiphallus; prg - pregonite; pog - postgonite. All photographs by J. Pohjoismaeki.

Figure 6. Comparison of Gymnocheta spp. female sternites and terminalia A ventral view of the sternites and terminalia of i G. lucida ii G. magna iii G. viridis and iv G. zhelochovtsevi B detail of the female terminalia of i G. lucida ii G. magna iii G. viridis and iv G. zhelochovtsevi. Note the long cerci in G. zhelochovtsevi. All photographs by J. Pohjoismaeki.

Figure 7. Maximum likelihood tree of the Co 1 sequences of the Nordic Gymnocheta spp. and related Ernestiini. Numbers at nodes indicate posterior probabilities and scale bar the relative sequence divergence. BOLD progress ID given before the species name and sample ID as well as GenBank access number given after it. The DNA barcodes do not differ between the Nordic G. zhelochovtsevi and G. viridis (BOLD: ACA 6555) but differ significantly from G. lucida (BOLD: ACF 3891) and G. magna (BOLD: ACA 9848).