Ephydrella bicolor, Mathis & Zatwarnicki NZAC, 2025

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 : 238

3. Ephydrella bicolor , sp. nov.

Figs. 17–23 , 38

Diagnosis.—This species is distinguished from congeners by the following combination of characters: Medium-sized shore flies, body length 3.30–3.90 mm;

Head ( Figs. 17–18 ): Mesofrons dark brown thinly microtomentose, subshiny; parafrons grayish to grayish blue anteriorly, charcoal black posteriorly; fronto-orbits dark brown, finely but densely microtomentose; ocelli arranged in isosceles triangle. Antenna grayish black to black, densely microtomentose. Face distinctly two-toned, hump of facial protrusion with at least dorsal half dark brown, thereafter ventrally bluish gray. Gena-to-eye ratio 0.31–0.40.

Thorax ( Fig. 19 ): Mesonotum mostly dark colored, brownish, but with some bluish gray coloration at lateral margins, especially at scutellar suture laterally. Acrostichal setulae, except for posterior pair, small, sparse, and not organized into rows. Wing: Veins and crossveins frequently darkened. Costal vein ratio 0.13–0.19; M 1 vein ratio 0.50–0.59. Femora and tibiae gray to grayish blue; tarsi blackish brown.

Abdomen ( Figs. 20–23 ): Tergites two-toned, anterior third of tergites dark brown, posterior portion grayish blue. Male terminalia ( Figs. 20–23 ): Epandrium in posterior view ( Fig. 20 ) only slightly higher than wide, dorsal margin arched, height of cercal cavity nearly half overall height of epandrium, in lateral view ( Fig. 21 ) with dorsal portion tapered to narrow, truncate dorsum, ventral portion semiquadrate, anterior margin irregular, posterior margin nearly straight; cercus in posterior view ( Fig. 20 ) drop-like, tapered dorsally, in lateral view ( Fig. 21 ) semihemispherical; surstyli in posterior view ( Fig. 20 ) very long, very gradually tapered, length equal to height of epandrium, apical third of surstylus slightly flared laterally, in lateral view ( Fig. 20 ) irregularly rectangular on basal 2/3, anterior margin of basal portion with obtusely pointed, apex of point narrowly truncate, apical third conspicuously tapered, shallowly curved anteriorly medial surstylar margin shallowly sinuous; medioventral process in posterior view ( Fig. 20 ) not extended, this area symmetrically sinuous; phallus in lateral view ( Fig. 23 ) longer than high, dorsal surface sinuous, ended apically with a tooth-like, obtuse, short pointed projection, in ventral view ( Fig. 22 ) with short concavity from phallapodeme dorsal extension, forming an obtuse point, thereafter apically lateral margins shallowly concavity to angulation, thereafter tapered to rounded apex; phallapodeme in lateral view ( Fig. 23 ) with keel twice as long as wide, keel broadly and evenly rounded, ventral extension (to postgonite) over twice length as dorsal extension (to base of phallus), in ventral view ( Fig. 22 ) a small, short rectangular basal process attached to a cap-like base; postgonite+hypandrium in lateral view ( Fig. 23 ) somewhat narrowly triangular, ventral margin straight, broadly truncate, dorsal margin nearly straight, ventroapical corner acutely pointed, basal forming angulate corner, in ventral view ( Fig. 22 ) with lateral margins curved, basal margin concave, apical 1/4 as 2 narrow, short, thin, tapered apical processes that barely extend beyond phallus apex.

Type Material.— The holotype male of Ephydrella bicolor is labeled “ NEW ZEALAND. CH. IS. Wharekuri (43°42.6'S, 176°35.05'W) 12 October 2002, D. and W.N. Mathis / HOLOTYPE ♂ Ephydrella bicolor Mathis & Zatwarnicki NZAC [red].”. Three paratypes (1♂, 2♀; USNM) bear the same label data as the holotype. Other paratypes are as follows: New Zealand. Offshore Islands. Chatham Islands. Chatham Island, Tuku (44°04'S, 176°36'W), 20 Feb 1967 (10♂, 4♀; NZAC, USNM). Mangere Island : Hut Peninsula (44°16.5'S, 176°18.1'W; shore rocks), 3 Dec 1992, J. W. Early (3♂, 1♀; AMNZ) .

Type Locality.—Australasian. New Zealand. Offshore Islands. Chatham Islands, Chatham Island, Wharekuri (field and beach; 43°42.6'S, 176°35.05'W) .

Distribution ( Fig. 38 ).—Australasian/Oceanian. New Zealand (Chatham Islands).

Etymology.—The species epithet, bicolor , has reference to the two-toned face, parts of the thorax, and abdominal tergites.

Remarks.—This species is only known thus far from the Chatham Islands (Chatham and Managere Islands) where two other congeners, E. aquaria and E. assimilis , are also known to occur sympatrically.

This species is distinguished from congeners, especially E. aquaria and E. assimilis , by the following combination of characters: facial protrusion or hump distinctly two-toned, hump of facial protrusion with at least dorsal half dark brown, thereafter ventrally bluish gray ( Figs. 17–18 ); mesonotum mostly brownish, but with some bluish gray coloration at lateral margins, especially at scutellar suture laterally; legs, including basitarsomeres, blackish brown; lateral surstylar processes very long and robust, length equal to height of epandrium, medial surstylar margin shallowly sinuous ( Figs. 20 ).

Figures

FIGURES 17–23. Ephydrella bicolor sp. nov. 17–19. Head and thorax. 17. Head, anterior view. 18. Head, lateral view. 19. Thorax, dorsal view. Scale bar = 0.5 mm. 20–23. Male terminalia (specimen from New Zealand. Tuku, 20 Feb 1967). 20. External structures, posterior view. 21. Same, lateral view. 22. Internal structures, ventral view. 23. Same, lateral view. Scale bar = 0.1 mm.

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.