Gymnocheta zhelochovtsevi 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 zhelochovtsevi Zimin

Gymnocheta zhelochovtsevi Zimin, 1958: 62. Holotype ♂ [ZIN] (see below).

Material.

Russia: ♂: Южные Курилы, Итуруп, Рыбаки, 5 км SW Курильска, В. Рихтер, 23. VI.1968 [Southern Kurils, Iturup, Ribaki, 5 km SW Kurilsk, V. Richter, 23. VI.1968], det. V. Richter. Dissected by V. Richter [ZIN]. Examined from high quality photographs, including the terminalia . Japan: ♂: JAPAN / Mt. Muine / Sapporo / HOKKAIDO / 20 Jun.1974 / K. Nishida // Gymnochaeta / zhelochovtsevi? / Zimin (handwritten) / det. H. Shima 1982 [BLKU] ; ♂: JAPAN / Hokkaido / Churui Vil. Haruyama / 1 Jul.1993 / A. Kuromoto // Gymnocheta ♂ / zhelochovtsevi Zimin / det. C. Bergström 2020 [BLKU]. Dissected . Finland: ♂: Regio aboensis, Salo, Halikko , Perkko , 67158-60:32853-8, 12.vi.2020, A. Haarto leg. [AHC], BOLD Sample-ID JP2020-G1 ; ♂: Karelia australis, Vehkalahti , 18.vi.1966, L. Tiensuu leg. Dissected. [MZH] ; ♀: Regio aboensis, Korppoo , 66840:31958, malaise, 19.vi.-22.vii.2003. A. Haarto leg. Dissected. BOLD Sample-ID JP2020-G2 ; 2♀♀: Regio aboensis, Salo, Halikko , Perkko , 671604:328551, 12.-28.vi.2020, malaise, Haarto leg. [AHC] ; 1♀: Regio aboensis, Salo, Halikko , Perkko , 67158-60:32853-8, 28.vi.2020, A. Haarto leg. [AHC] . Sweden: 1♀: S. Vb: Umeå: Tavelån: / Oestra Tjaelamark ; malaise / RT 90 70952, 17177 / 10.v.-16.vi.2016 / S. Hellqvist 14947 // Gymnocheta ♀ / zhelochovtsevi Zimin / det. C. Bergström 2020 [CBC] .

Diagnosis.

Gymnocheta zhelochovtsevi is characterised by a dark, almost black metallic green, wide frons in both sexes, and a hooked syncercus in the male.

Redescription. Body length: 9.2-10.4 mm (n = 7).

Male (Figs 2D , 4C , Eiv, 5A:iv, B:iv, C:iv).

Colouration: Head covered with dense greyish or yellowish white microtomentum. The metallic ground colour is only weakly shining through, similar as is seen with G. lucida . Facial plate black without a metallic green spot. Occiput, postgena, genal dilation, ocellar triangle and frontal plate almost black in ground colour, although a hint of dark metallic bronze-green shine can be seen with changing light incidence. Palpus clypeus and prementum black, labella dark brown. Thorax and abdomen dark metallic green in ground colour, not as lucid as in G. magna or G. viridis and covered with indistinct greyish white microtomentum. Scutum, when viewed from the side and slightly from behind, with four pronounced longitudinal stripes of microtomentum, changing from grey to purple depending on the direction of the incident light. Proepisternum black and with thin grey microtomentum. Legs extensively black, but fore coxa in anterodorsal region and sometimes also femora with remnants of metallic shine, covered with light grey microtomentum. Wing membrane around crossvein r-m not infuscated.

Head (Fig. 2A ): Frons at its narrowest point, 0.53-0.68 (n = 5) × as wide as an eye in dorsal view. Frontal vitta almost parallel-sided in anterior part hardly tapering until closely before ocellar tubercle. Head in profile protruding at level of antennal insertion, width of parafacial at this level ca. 0.65-0.75 × (n = 2) the horizontal eye diameter. Fronto-orbital plate with a row of 10-12 medioclinate moderately strong frontal setae and some additional setulae, uppermost setula tiny and sometimes slightly reclinate, four or five setae extend to the middle of the pedicel with the row curving laterally; fronto-orbital plate outside the frontal row of setae with 4-10 sparsely spread, short and tiny setulae. Height of face 0.8-0.9 × the length of frons (n = 2). Gena in profile at narrowest point, 0.4-0.5 (n = 2) × as high as vertical eye diameter. Facial plate and lower facial margin not visible in profile. Facial ridge on less than lower 1/5 with one or two strong, two additional thinner supravibrissal setae, and four or five setulae. Ridge below vibrissa with 3-5 strong subvibrissal setae continuous with the genal setae, longest ca. 0.6 × the length of vibrissa. Inner vertical setae strong and crossed, longer than the ocellar setae; outer vertical setae subequal with inner vertical setae, distinctly stronger than the postocular setae. Postocular setae short and barely bending forward over the eyes. Occiput with a pair of postocellar setae, weaker that the outer vertical setae, thinner but longer than the postocular setae. Palpus slightly clavate at tip, subequal to the length of the antenna and densely covered with short black setulae, two strong preapical setulae and 4-5 irregular ventral setulae. Antenna: Pedicel subtriangular and with one elongate seta, 1.2-1.5 × as long as wide at apex (n = 4). First flagellomere 1.5-1.7 × (n = 5) as long as the pedicel, in profile subrectangular, rounded at apex; maximal width in profile as wide (0.9-1.1) (n = 2) as parafacial at narrowest point. Eyes sparsely covered with, compared with the other species, relatively short whitish hairs with a yellowish tint.

Thorax: Prosternum bare. 2(3)+3 acrostichal, 3+4 dorsocentral and 1+3 intra-alar setae. Ground vestiture on scutum (consisting of thin setulae) sparse and erect, longest setulae 0.5-0.6 × as long as the shortest setae, anteriorly shorter, at most 0.3 × the length of the setae. Scutellum with four pairs of strong marginal setae, mixed with some shorter and weaker marginal setae/setulae, almost horizontal with the plane of scutellum, apical setae missing; subapical setae close to the apex, parallel or slightly diverging, two lateral pairs and one basal pair; four suberect preapical discal setae, forming a row in front of the marginal setae, the strongest pair in the middle sometimes subequal to the lateral setae, mixed with numerous tiny setulae the longest at least 1/2 as long as the strong preapical setae.

Legs: Claws and pulvilli on fore legs ca. 1.0 (n = 3) × as long as tarsal segment 5, the latter 2.0 (n = 3) × as long as tarsal segment 4. Fore tibia with a row of 5-7 anterodorsal setae, 3-5 setae in an irregular posterodorsal row and two posterior setae; preapical anterodorsal seta well developed, subequal with the preapical dorsal and preapical posterior setae. Mid tibia with a row of five anterodorsal setae the strongest in the middle, four or five posterodorsal setae, two or three posterior setae, one strong ventral seta accompanied by a shorter seta above. Preapical anterodorsal seta of the hind tibia subequal to the preapical dorsal seta, preapical anteroventral seta 1/2 the length of anterodorsal seta; a continuous irregular row of 8-10 anterodorsal setae, three or four posterodorsal setae and three or four anteroventral setae.

Wing: One or two costal spines, the strongest lower spine 2-3 × as long as the surrounding costal setulae. Fourth and fifth costal section ca. 2 × as long as sixth costal sector. Vein R4+5 at node with four ventral and three or four dorsal setulae. Cell r4+5 often somewhat narrow at wing edge, 0.8 × the length of crossvein r-m.

Abdomen (Fig. 4C ): Domed, ground-vestiture prone or semierect on tergite 5, also ventrally. Tergite 2 with two lateral setae on each side. Tergite 3 with two pairs of median discal setae; with a pair of median marginal setae and two or three lateral setae on each side. Tergite 4 similarly with two or three pairs of unequally and irregularly set strong median discal setae, in dorsal view with a full row of 10-12 marginal setae. Tergite 5 with two or three irregular rows of unequally strong discal setae and a row of strong marginal setae.

Terminalia (three dissections) (Figs 4C , Eiv, 5A:iv, B:iv, C:iv):

Sternite 5 (Fig. 4C , Eiv) in ventral view with long and wide lobes; length of medial cleft 1.3-1.4 × its maximal width. Lobes with numerous setulae, apex in ventral view rounded in a ventral and slightly lateral view with a subtriangular appearance. Dorsomedial process long and narrow, indistinct, and visible only as a callosity, along its length connected with the lobes. Basal plate bare, ca. 0.4 × as long as sternite 5 and 2.6-2.7 × as wide as long. Syncercus in profile (Fig. 5A :iv) dorsally strongly bowed in the middle and with a characteristic tooth-like hook at the apex, reminiscing of the situation in Gymnocheta porphyrophora Zimin (1958); in caudal view (Fig. 5B :iv) subtriangular with long basal lobes and a widened apex; dorsolateral with numerous long setulae that generate a dense and fur-like hairiness. Surstylus (Fig. 5A :iv) bacilliform, straight in caudal view, in profile gradually tapering at base, then slightly arch-like bent at middle; evenly thick apart from an indicated widening at apex, bent towards syncercus. Pregonite rodlike in caudal view; lobe-like in profile (Fig. 5C :iv) with a wide hook-like projection apically, shortly tapering at apex. Aedeagus: Basiphallus with a basal projection and a distinct digitiform epiphallus, resembling the preceding species. Distiphallus (Fig. 5C :iv) in profile compact and evenly wide.

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

Colouration: Fronto-orbital plate almost entirely metallic dark green when viewed from behind and slightly from above; the metallic ground colour at least partly interrupted on the upper part of parafacial. However, most of the metallic ground colour on upper part of parafacial and anterior 1/3 of fronto-orbital plate is covered by greyish white microtomentum, which is dense especially along eye margin and frontal setae.

Head (Fig. 3D ): Frons wider, at its narrowest point 0.8-1.0 (n = 4) × as wide as an eye in dorsal view. Frontal vitta wide and with parallel edges in anterior 1/2 and then slightly tapering towards ocellar tubercle, its width at ocellar tubercle exceeding the width of fronto-orbital plate at this point. Fronto-orbital plate normally with fewer, 6-9 moderately strong medioclinate frontal setae. Outer vertical setae strong and 0.6-0.7 × the length of inner vertical setae, stronger than ocellar setae. Postocellar setae subequal with the upper postocular setae. First flagellomere 1.3-1.5 (n = 4) × as long as pedicel, normally as wide as, or slightly wider than the parafacial at narrowest point.

Thorax: Whitish grey microtomentum normally thinner than in males, most intense on the pleura and episternum.

Legs: Claws and pulvilli on fore legs shorter ca. 0.7-0.8 (n = 5) × as long as tarsal segment 5, the latter 1.5-1.6 (n = 5) × as long as tarsal segment 4.

Abdomen: Tergites 3 and 4 with one or two pairs of median discal setae. Tergite 5 trapezoid, along anterior margin ca. 2 × as wide as long, posterior edge concave (blunt or pointed in G. lucida ). Sternite 5 slightly wider than long, with 4 strong setae along posterior margin (Fig. 6A :iv).

Terminalia (one dissection) (Fig. 6A :i, B:i): Tergite 6 divided into narrow and somewhat elongated hemitergites, widely separated, each closely accompanied by a pair of setulae at posterior margin. Sternite 6 shorter, 0.5 × as long and 1.2 × as wide as sternite 5 (n = 1), with ca. 10 tiny setulae along the posterior margin. Tergite 7 strongly reduced. Sternite 7 semi-spherical, ca. as long but slightly narrower than sternite 6, with numerous setulae most of them tiny, restricted to the posterior margin. Sternite 8 strongly reduced, partly hidden below sternite 7. Hypoproct (Fig. 6B :iv) in ventral view almost triangular, pointed, apex only slightly rounded, densely covered with setulae that are longer laterally; in profile slightly bent towards the cerci, apex of hypoproct not reaching the tip of cerci. Cerci elongated, with numerous setulae of varying length, the strongest setulae in profile subequal to the length of sternite 7.

DNA.

Despite the morphological differences, G. zhelochovtsevi shares Co1 DNA barcode sequence with G. viridis (Fig. 7 ). DNA barcode sharing is not uncommon in Tachinidae ( Pohjoismäki et al. 2016).

Distribution.

Like G. lucida , G. zhelochovtsevi had been thought to be an Eastern Palaearctic species ( Richter 2004). So far, the only records from Europe are the ones listed here from the southern and southwestern coast of Finland and from Sweden.

Biology.

The specimens from Halikko were collected from a flood meadow adjacent to a meandering stream. The meadow is characterised mainly by tall grass and sedges, surrounded by shrub of willows ( Salix spp.) and bird cherry ( Prunus padus L.). One male and one female were hand netted from the flowers of Anthriscus sylvestris (L.) and two females were collected with a Malaise trap. The female specimen from Korppoo was caught in a Malaise trap in a seashore meadow, surrounded by shrub of meadowsweet ( Filipendula ulmaria (L.)) and alders ( Alnus spp.). The Swedish specimen was collected in a Malaise trap, placed close to the calmly flowing, slightly meandering, ca. 5 m wide Tavelån River. The trap was placed in overgrowth known as “raningsmark”; i.e., grassland long ago used as a hay meadow or grazing but now characterised by bush wood with meadow glades between the shrubbery.

Notes.

Lauri Tiensuu mentioned on page 138 of his unpublished notes that a specimen identified by him as a female of G. viridis , but actually a male of G. zhelochovtsevi , was collected around (on?) aspen ( Populus tremula L.) trunks near the village of Salmenkylä in the former municipality of Vehkalahti. The original description by Zimin was based on one male specimen, whose fifth sternite was poorly illustrated and the epandrium not illustrated at all in the original publication. The tip of the syncercus of the species has a characteristic hook (Figs 4C , 5A :iv), somewhat resembling that of Gymnocheta porphyrophora , which caused us some confusion. However, the median lobes at the posterior edge of the sternite of G. porphyrophora are well developed (Fig. 4D ), unlike in any of the other species discussed here.

Figures

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 4. Fifth sternites of Gymnocheta spp. males A Gymnocheta lucida male abdomen. Note the narrow profile of the posterior edge of the fifth sternite (arrow) B the edge of the fifth sternite in G. viridis is bulky and protruding beyond the tip of the abdomen, clearly recognisable from the side C the posterolateral lobe of G. zhelochovtsevi is somewhat subrectangular as in G. magna, but more rounded in profile. Note the apical hook of the syncercus D in contrast to G. zhelochovtsevi, posterior edge of fifth sternite in G. porphyrophora with well-developed median lobes (arrow) E dissected fifth sternites of Nordic Gymnocheta spp. in comparison: i) G. lucida, ii) G. magna, iii) G. viridis and iv) G. zhelochovtsevi. A distinct dorsomedial process present in G. magna and G. viridis Abbreviations: bpl - basal plate; dmp - dorsomedial process; mcl - median cleft; pll - posterolateral lobe; tms - transversal median stripe; wll - wart-like lobe (or median lobe). Photograph D by V. Neimorovets, rest by J. Pohjoismaeki.

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).