Hydrellia dolezali, Zatwarnicki & Kejval, 2024

Hydrellia dolezali sp. nov.

( Figs 1–7 View Figs 1–7 )

Type locality. Czech Republic, Plzeň- Bolevec, banks of Velký Bolevecký rybník (pond), 49°46′33.5″N 13°23′27″E, altitude 310 m ( Fig. 34 View Figs 34–37 ).

Type material. HOLOTYPF: J, labelled: ʽCZ-Bocc 6246, 18.7.2023, PLZEŇ- Bolevec, Velký bolevecký rybník (pond banks), 310 m, Z. Kejval leg., 49°46′39″N 13°23′37″E [printed] // HOLOTYPE [red label, printed] // Hydrellia dolezali sp.nov. T. Zatwarnicki & Z. Kejval det. 2024 [printed]ʼ ( NMPC). PARATYPFs: 2 JJ 1 ♀, same locality data as holotype ( NMPC); 10 JJ 14♀♀, same locality data as holotype, except: 27.8.2024 (12 ex. in NMPC, 4 ex. in each CULSP, MCH, ZCM); 9 JJ 5 ♀♀, ʽCZ-Bocc 5845, 20.8.2024 1 km E of ALBEŘICE, pond banks/ littoral, 610 m, Z. Kejval leg. 50°09′44″N 13°10′58″E [printed]ʼ ( NMPC, SMOC); 1J, ʽCZ-Bmer 6548, 23.8.2024 1.5 km SE of TCHOŘOVICE, Smyslov Res., pool banks/littoral, 460 m, Z. Kejval leg., 49°25′19″N 13°48′05″E [printed]ʼ ( NMPC). GoogleMaps

Description. Male. Small shore flies, body length 2.1–2.4 mm; wing length 2.4–2.6 mm.

Head. Frons strongly transverse; parafrons dark, brownish, frontal vitta concolorous with parafrons ( Fig. 2 View Figs 1–7 ); pseudopostocellar seta nearly as long as inner vertical seta; ocellar seta more delicate and about 0.5 times as long as pseudopostocellar seta; fronto-orbital setae moderate, both distinctly shorter than pseudopostocellar seta.Antenna with scape and pedicel black, basal flagellomere black ( Figs 1, 2 View Figs 1–7 ); arista with 7 dorsal rays. Lunula grey; face in anterior view grey, brownish medially, in lateral view moderately arched; 6 facial setulae; palpus black, spatulate ( Fig. 2 View Figs 1–7 ); eye to gena ratio 7.0.

Thorax. Mesonotum entirely dark, unicolorous dark brown, subshiny with slight bluish-green reflection; pleurae grey, with bluish tinge ( Fig. 1 View Figs 1–7 ). Presutural dorsocentral setae small. Legs nearly entirely black, largely covered by grey microtomentum, trochanters partly with brownish tinge; mid tibia rather robust; fore femur bears postero-ventral row of small setulae; distal half of mid femur bears anterior row of moderate setulae. Wing hyaline with pale brownish veins, becoming darker distally; costal vein ratio 0.71; M vein ratio 0.73; knob of halter white, stem brown.

Abdomen. All terga dark brown, unicolorous, subshiny, with slight bluish-green reflection; male fifth to fourth tergite ratio 1.0. Epandrium in dorsal view narrowly U-shaped with rather wide lateral arms producing moderate cercal cavity, arms in lateral view allantoid, each bearing 4 strong setae; cercus in dorsal view semi-circular ( Fig. 3 View Figs 1–7 ), area between cerci and genital plate membranous and closed laterally by cordate sclerites; genital plate in dorsal view 1.22 times longer than wide, trapezoidal, with anterior margin cleft medially, and 8–9 conspicuous setulae on each corner ( Fig. 3 View Figs 1–7 ), in lateral view narrowly triangular; aedeagus elongate, in dorsal view 3.68 times longer than wide, spatulate with posterior margin slightly concave, sharply narrowed at 1/3 of its length, then tapered with wavy edges, apically mucronate ( Fig. 4 View Figs 1–7 left), in lateral view 3.80 times as long as wide, with posterior part uncinate, having rectangular base, and anterior part clavate, evenly tapered apically ( Fig. 4 View Figs 1–7 right); phallapodeme elongate, in dorsal view bar-like and moderately bifurcate anteriorly ( Fig. 5 View Figs 1–7 ), in lateral view slightly sinuate and bearing ventral excurvate triangular attachment at midlength ( Fig. 6 View Figs 1–7 ); postgonite forming arcuate spatula, with widened posterior section, its anterior process Z-shaped ( Fig. 7 View Figs 1–7 ); pregonite robust and long bifurcate apically, each process bearing apical setula ( Fig. 7 View Figs 1–7 ); hypandrium in dorsal view forms squircle (combination of rectangle and semi-circle) with rounded anterior margin ( Fig. 5 View Figs 1–7 ), in lateral view shoeshaped with arcuate ventral margin ( Fig. 6 View Figs 1–7 ); 5 th sternum U-shaped with numerous robust setulae, evenly pointing posteriad; setulae unevenly arranged and spaced, markedly longer and more dense along posterior margin and rather small and scattered more anteriorly ( Fig. 5 View Figs 1–7 ).

Female. Identical with male for most external characters; body length 2.5–2.8 mm; wing length 2.6–2.8 mm; mid tibia not thickened (slender, compared to males).

Differential diagnosis. Hydrellia dolezali sp. nov. is undoubtedly close to H. caledonica Collin, 1966 as suggested by overall similarity of male characters. It can be distinguished from this species by black palpi, 6–7 aristal rays, more elongate aedeagus (2.6 times as long as wide in dorsal view for H. caledonica ) that is narrowed in apical portion, equally-long projections of pregonites, and by uneven setation of sternite 5 (more evenly developed, with setulae on anterior portion more robust/dense and pointing anteriad for H. caledonica ).

Etymology. The species epithet, dolezali , is a genitive patronym to honor the late Zdeněk Doležal (1957–2007), a Czech entomologist and nature painter from Pilsen, who dealt with various groups of insects, including Diptera (mainly Syrphidae ), and who was a great guide for the second author during his first excursions in the vicinity of Plzeň- Bolevec.

Biology. All specimens were collected exclusively by sweeping littoral vegetation of ponds/pools with extensive stands of Eleocharis palustris ( Figs 34, 36 View Figs 34–37 ), which may be the host plant of this species. At the type locality these stands were isolated from other vegetation, situated in rather deep water (50–90 cm) and flies were also observed on stems of this plant, usually close to the water surface ( Fig. 34 View Figs 34–37 ).

Distribution. Czech Republic.