Ephydrella thermarum Dumbleton

Mathis, Wayne N. & Zatwarnicki, Tadeusz, 2025, A review of Ephydrella Tonnoir and Malloch from the New Zealand subregion (Diptera: Ephydridae) with description of a new species, Zootaxa 5673 (2), pp. 227-251 : 247-248

7. Ephydrella thermarum Dumbleton

Figs. 39 , 44–50

Ephydrella thermarum Dumbleton 1969: 39 [immature stages].— Winterbourn 1969: 463–4 [ecology]; 1973: 72–78 [ecology].— James 1985: 440 [list].— Mathis 1989: 648 [Australasian/Oceanian catalog].— Mathis and Zatwarnicki 1995: 248 [world catalog].— Winterbourn et al. 2000: 82 [review, larvae].

Diagnosis.—This species is distinguished from congeners by the following combination of characters: Moderately large to large shore flies, body length 4.50–5.35 mm.

Head ( Figs. 44–46 ): Frons and face brown, generally densely microtomentose except for shiny mesofrons, which is mostly shiny, metallic bluish green to bronze, lacking distinctive gray area laterally. Facial protrusion or hump unicolorous. Gena-to-eye ratio 0.32–0.36.

Thorax ( Figs. 44–46 ): Mesonotum generally dark colored, brown to blackish brown; pleural areas brown to gray. Wing faintly to darkly infuscate, brown; costal vein ratio 0.23–0.30; M 1 vein ratio 0.66–0.74. Legs, including basitarsomere, blackish brown.

Abdomen ( Figs. 47–50 ): Tergites dark colored, shiny dark blue, each tergite becoming slightly grayer toward posterior margin. Male terminalia ( Figs. 47–50 ): Epandrium in posterior view ( Fig. 47 ) with width nearly 2/3 height, dorsal margin broadly rounded, in lateral view ( Fig. 48 ) with basal portion rectangular, dorsal position tapered to narrowly truncate dorsum; surstyli in posterior view ( Fig. 47 ) with apical ¾ parallel-sided, straight, evenly setulose an lateral and medial margins, apex bluntly rounded, in lateral view ( Fig. 48 ) appearing more robust than posterior view, digitiform, anterior margin sinuous with midlength bulge, posterior margin nearly straight; ventromedial process short in posterior view ( Fig. 47 ), triangular, each half narrow, tapered to relatively sharp point; phallus in lateral view ( Fig. 50 ) higher than long, truncate apically, ventral margin broadly truncate, at most shallowly concave, in ventral view ( Fig. 49 ) twice as narrow basally as subapical width, lateral margins shallowly sinuous, apical third tapered medially to broadly pointed apex; phallapodeme in lateral view ( Fig. 50 ) elongate, narrow, with distinctly projected keel, keel occupying medial third, ventral extension (to postgonite) and dorsal extension (to base of phallus) comparatively elongate, about equal in length, in ventral view ( Fig. 49 ) elongate, conspicuously tapered to apex, lateral margin shallowly concave, basal margin broadly, shallowly concave; postgonite+hypandrium in lateral view ( Fig. 50 ) elongate, base as a dorsally curved tapered projection, dorsal margin essentially straight on basal half to a third, thereafter angulate then shallow concave to apex, apical fourth narrow, shallowly curved, acutely pointed, ventral margin broadly and angularly concave, in ventral view ( Fig. 49 ) with lateral margins bluntly projected, thereafter basally tapered to phallapodeme, anterior half likewise tapered medially, elongate, narrow to apical fourth, latter section very narrow, angled lateroapically.

Primary Type Material.— The holotype male is labeled “ Ephydrella thermarum Dumb. [handwritten]/[ New Zealand.] Black Terraces TAUPO. 25.X.66. [25 Oct 1966] J. S. Armstrong [handwritten]/ HOLOTYPE ♂ [handwritten].” The holotype is double mounted (minuten in a rectangular block of polyporus), is in excellent condition, and is deposited in the NZAC .

Type Locality.— Australasian : New Zealand. North Island. Taupo, Black Terraces (38°41.1'S, 176°04.2'E) .

Specimens Examined from New Zealand. — NORTH ISLAND. BP: Old Waiotapu Road (hot spring; 38°19.6'S, 176°22.5'E), 8 Feb 1998, V. Hollmann, W. N. Mathis (10♂, 12♀; NZAC, USNM) ; Rotorua , Waimangu (38°17.1'S, 176°23.7'E), 21 Nov 1974, A. K. Walker (2♂; NZAC, USNM) ; Rotorua , Waimangu, Trinity Terrace (38°17'S, 176°24'E), 19 Dec 1969, L. M. Brock (1♂, 6♀; USNM) ; The Caudron , Waimangru Valley (38°17.2'S, 176°23.4'E), 10 May 1971, K. A. J. Wise (3♀; AMNZ) . TO: Taupo , Black Terraces (38°41.1'S, 176°04.2'E), 23 Oct 1966, J. S. Armstrong (7♂, 9♀; paratypes; NZAC) ; Taupo (38°41.1'S, 176°04.2'E; hot spring), 25 Oct 1966, J. S. Armstrong (1♂, 1♀; USNM) ; Taupo , DeBrett Hotel / Spa (38°41.1'S, 176°04.2'E), 24 Dec 1969, L. M. Brock (3♂, 2♀; USNM) ; Tokaanu (38°57.3'S, 175°45'E; hot springs), 20 Feb 1965, G. Kuschel (6♂, 2♀; NZAC) . Tongarivo National Park , Hitetake (38°57.3'S, 175°45'E; hot springs), 23 Dec 1969, L. M. Brock (1♂, 2♀; USNM) . Orakei Korato (38°28.4'S, 176°08.3'E; hot springs), 25 Dec 1969, L. M. Brock (1♂, 3♀; USNM) .

SOUTH ISLAND. DN: Otago Peninsula, Hoopers Inlet (45°51.1'S, 170°39.7'E); 13 Jan 2004, W. N. Mathis (1♂, 1♀; USNM) . MC : Christchurch (43°31.9'S, 172°38.2'E), 17 Feb 1922, A. Tonnoir (1♀; paratype; USNM); Christchurch ( Styx Mill Reserve ; 43°28.1'S, 172°36.4'E), 17 Oct 2002, D. and W. N. Mathis (2♂; USNM); Christchurch , Travis Marsh (43°29.1'S, 172°41.8'E), 21 Dec 1995 , R. P. Macfarlane (5♂, 3♀; CMNZ) .

Distribution ( Fig. 39 ).—Australasian/Oceanian: New Zealand. North Island (BP, TO). South Island (DN, MC).

Natural History.—This species feeds on algae that are usually associated with hot springs (38–48°C) in the central North Island ( Winterbourn 1968, 1969, James 1985). On South Island the species has been found in Copeland Hot Springs ( Winterbourn 1973) but also at sites in Christchurch.

Remarks.—This species is distinguished from congeners from New Zealand, especially E. aquaria , by the following combination of characters: facial protrusion or hump unicolorous; mesonotum mostly shiny, metallic bluish green to bronze, lacking distinctive gray area laterally; legs blackish brown, including basitarsomeres; surstyli relatively long and narrow, about 6X length of medial process, parallel sided, apex rounded; medial and lateral margins of surstyli bearing minute but conspicuous setulae evenly along length.

Figures

FIGURES 38–43. Distribution maps and male terminalia of Ephydrella. 38–39. Distribution maps. 38. E. bicolor sp. nov. (stars) and E. novaezealandiae (Tonnoir & Malloch) (circles). 39. E. spathulata Cresson (stars) and E. thermarum Dumbleton (circles). 40–43. Male terminalia of E. spathulata Cresson (specimen from New Zealand. Berwen Station, 2 Feb 2002, R. P. Macfarlane). 40. External structures, posterior view. 41. Same, lateral view. 42. Internal structures, ventral view. 43. Same, lateral view. Scale bar = 0.1 mm.

FIGURES 44–46. Head and thorax of Ephydrella thermarum Dumbleton. 44. Latero-oblique view. 45. Lateral view. 46. Dorsal view. Scale bar = 0.5 mm.

FIGURES 47–50. Male terminalia of Ephydrella thermarum Dumbleton (specimens from New Zealand. Old Waiotapu Road, 8 Feb 1998, W. N. Mathis). 47. External structures, posterior view. 48. Same, lateral view. 49. Internal structures, ventral view. 50. Same, lateral view. Scale bar = 0.1 mm.