Ephydrella assimilis (Tonnoir and Malloch)

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 : 235-237

2. Ephydrella assimilis (Tonnoir and Malloch)

Figs. 1–3 , 9–16

Ephydra (Ephydrella) assimilis [also as similis] Tonnoir and Malloch 1926: 7.

Ephydrella assimilis .— Miller 1950: 111 [catalog of New Zealand Diptera ].— Harrison 1959: 247 [generic combination, fauna of New Zealand].— Mathis 1989: 647 [Australasian/Oceanian catalog].— Mathis and Zatwarnicki 1995: 247 [world catalog].

Ephydra assimilis .— Bock 1987: 155 [alternate original name selected].

Diagnosis.—This species is distinguished from congeners by the following combination of characters: Medium-sized to moderately large shore flies, body length 3.40–4.10 mm. Body generally bluish gray, densely microtomentose, mostly dull, at most subshiny.

Head ( Figs. 1 , 10–12 ): Frons with mesofrons shiny, metallic dark blue to dark green; parafrons microtomentose, gray to charcoal, velvety just medial of lateroclinate fronto-orbital setae. Facial protrusion or hump unicolorous, dark brown, becoming grayer ventrally, especially along oral margin. Gena-to-eye ratio 0.35–0.40. Cibarium ( Fig. 1 ) 2.3 higher than wide, its dorsal portion W-shaped with long lateral processes; medial sensillae arranged in a sinuous line, its number about 40; posterior sensillae absent.

Thorax ( Figs. 10–12 ): Mesonotum mostly shiny, metallic bluish green to bronze, lacking distinctive gray area laterally; acrostichal setulae generally arranged in 2 conspicuous rows; mesopleuron distinctive gray area laterally from postpronotum through notopleuron. Acrostichal setulae generally arranged in 2 rows. Costal vein ratio 0.18– 0.24; M 1 vein ratio 0.70–0.75. Legs blackish brown with basitarsomere of middle leg yellowish brown.

Abdomen ( Figs. 13–16 ): Tergites generally microtomentose, gray to greenish gray, dull but with some metallic reflections especially toward anterior portion of each tergite, transition slight. Male terminalia ( Figs. 13–16 ): Epandrium in posterior view ( Fig. 13 ) high, width about 2/3 height; lateral surstylar process relatively short and slender, about 4X length of ventromedial process or less than height of epandrium; surstyli in posterior view ( Fig. 13 ) with lateral margins distinctly sinuous with 2 shallow excavations, apical surstylar extensions oriented laterally; cercal cavity in posterior view ( Fig. 13 ) about 1/3 height of overall epandrial height; cercus in posterior view ( Fig. 13 ) narrowly drop-like, in lateral view ( Fig. 14 ) ovate; ventromedial process comparatively large, height equal to half extended surstylar process, triangular; phallus in lateral view ( Fig. 14 ) longer than high, basal 2/3 with dorsal surface sinuously and somewhat irregularly curved, ended apically with a tooth-like, obtuse, short pointed projection, thereafter apically abruptly narrowed, base parallel-sided to acutely tapered apex, in ventral view ( Fig. 15 ) with basal ¾ as an irregular rectangular, lateral margins expanded gradually to rounded shoulder, apical ¼ a medial, triangle, pointed apically; phallapodeme in lateral view ( Fig. 16 ) with keel twice as long as wide, keel broadly rounded, ventral extension (to postgonite) over twice length as dorsal extension (to base of phallus), in ventral view ( Fig. 15 ) A-shaped, acutely pointed toward base; postgonite+hypandrium in lateral view ( Fig. 16 ) somewhat irregularly rectangular, dorsal margin broadly arched, ventroapical corner acutely pointed, ventral margin truncate to basal angulate corner, in ventral view ( Fig. 15 ) with lateral margins of basal portion curved, base forming an oval, apical 1/3 as 2 narrow, thin, tapered apical processes that extend beyond phallus apex. Female ventral receptacle with operculum large, helmet-like ( Figs. 2–3 ) with the width of the operculum slightly greater than height of extended process.

Type Material.— The holotype male of Ephydrella assimilis (Tonnoir and Malloch) is labeled “[ New Zealand.] Wharekauri, Chatham Is. , 12–14 Dec., 1923, C. Lindsay. / TYPE Ephydra assimilis T and M[,] A. Tonnoir det. [pink; species name and “ T and M” handwritten].” The holotype is double mounted (short pin in small rectangular sheet of celluloid), is in excellent condition (apex of abdomen removed, mounted on small celluloid slide that is attached to the main pin beneath the locality label), and is deposited in the NZAC. One female paratype with the same locality label data is in the USNM .

Type Locality.— Australasian: New Zealand. Off Shore Islands . Chatham, Wharekauri (43°42.6'S, 176°35.05'W) .

Specimens Examined from New Zealand. — NORTH ISLAND. AK : Cowan Bay (36°27'S, 174°42.2'E; 5 m), 1 Jan 2004, J. W. Early (1♀; AMNZ); Karekare (36°51.8'S, 174°28.4'E), 5 Feb 1989, V . Hollmann (1♀; NZAC); Karekare (beach; 37°00.2'S, 174°28.8'E), 10 Oct–1 Jan 2002, 2004, D. and W. N. Mathis (25♂, 1♀; USNM); Puketutu Island (36°57.8.5'S, 174°44.7'E; near Mangere), 26 Oct 1959, J. S. Armstrong (4♀; NZAC). CL : Mayor Island , NW Bay (37°17.4'S, 176°14.1'E), 8 Dec 1966, K. A. J. Wise (1♀; AMNZ). ND : Ahipara Plateau (35°11.3'S, 173°11.5'E), 16 Dec 1985, R . F. Gilbert (3♂, 3♀; AMNZ); Mangonui County, Taputaputa (stream near Cape Reinga ), 6 Mar 1976, K. A. J. Wise (1♂; AMNZ). TK: Mangarei , Waiwakaiho River (above Mangarei Stream), 9 Apr 1987, K. A. J. Wise (1♂, 3♀; AMNZ). TO : Tongariro River (40°03.7'S, 175°49.1'E), 1 Jan 1971, J. Gillespie (2♂, 3♀; NZAC). WI : Turakina beach (S of Wanganui; 40°04.3'S, 175°07.9'E), 9 Nov 1977, E. I. Schlinger (2♂, 4♀; NZAC). WN : Paekakariki , Queen Elizabeth Park (40°57.6'S, 174°58.4'E), 11 Nov 1977, E. I. Schlinger (1♂; NZAC); Paiaka (35°31.5'S, 174°09'E), 15 Feb 1950, RAC (3♂, 1♀; NZAC); Waikanae Beach (40°52.3'S, 175°0.5'E), 6–7 Jan 2004, W. N. Mathis (27♂, 5♀; USNM). WO : Raglan (37°49.6'S, 174°53.6'E; freshwater pond), 17 May 1971, J. Gillespie (3♂, 5♀; NZAC) .

SOUTH ISLAND. CL: Mararoa River (45°32.5'S, 167°53.2'E; 295 m), 25 Jan 2004, W. N. Mathis (11♂, 2♀; USNM) . DN : Warrington (45°42.5'S, 170°35.4'E; beach), 11 Dec 1977, E. I. Schlinger (1♂; NZAC) . FD : Te Anau (45°25.3’S, 167°42.9’E; 205 m), 23 Jan 2004, W. N. Mathis (1♀; USNM) . KA: Black Miller Creek (42°13.6’S, 173°51.1’E), 14 Feb 1998 , V. Hollmann (1♀; NZAC); Hapuku Stream (42°13’S, 173°45.3’E; 420 m), 8 Jan 2004, W. N. Mathis (2♂; USNM); Seddon ( Awatere River ; 41°39.6’S, 174°04.6’E), 14 Feb 1998 , V. Hollmann, W. N. Mathis (41♂, 17♀; NZAC, USNM); South Bay, Kaikoura (42°25.5’S, 173°40.9’E), 15 Feb 1969 , R. Emberson (2♀; LUNZ); Waima River (41°54.2’S, 174°6.8’E), 8 Jan 2004, W. N. Mathis (7♂, 1♀; USNM) . MC : Akaroa (43°48.2’S, 172°58.1’E), 9–10 Dec 1924, A. Tonnoir (4♂, 3♀; paratype; CMNZ, NZAC, USNM); Avon Heathcote (43°33.4’S, 172°42.1’E; mud flats), 5 Jan 1977, P. G. McGregor (2♂; CMNZ); Banks Peninsula, Little River (8 km S Bailey’s Road; 43°46.6’S, 172°45’E), 13 Dec 1977, E. I. Schlinger (1♂; NZAC); Christchurch (43°31.9’S, 172°38.2’E), 17 Feb 1922, A. Tonnoir (1♂; paratype; NZAC); Greenpark (43°41’S, 172°30.4’E), 17 Oct 1972 , R. A. Harrison (1♂, 2♀; LUNZ); Lake Ellesmere (43°47.7’S, 172°39.9’E; northeast coast), 22 Apr 1970, B. J. Donavan (2♂, 2♀; NZAC); Lake Pearson (43°06.1’S, 171°46.5’E; near Cass), 30 Nov 1977, E. I. Schlinger (1♂, 1♀; NZAC); Pleasant Point (44°15.6’S, 171°07.8’E), 20 Nov 1970, P. M. Johns (2♂, 3♀; CMNZ); Scotsburn Stream, Peel Forest (43°55.2’S, 171°15.8’E), 4 Dec 1977, P. G. McGregor (1♀; CMNZ) . NC: Hurunui River (near mouth; 42°54.6’S, 173°16.7’E), 14–15 Feb 1998 , V. Hollmann, W. N. Mathis (25♂, 16♀; NZAC, USNM); Napenape Scenic Reserve, Hurunui River Mouth (42°54.5’S, 173°16.7’E), 17 Nov 1977, E. I. Schlinger (21♂, 23♀; NZAC) . NN : Farewell Spit (40°31'S, 172°52'E), 4–11 May 1977 (2♀; CMNZ) . OL : Mararoa River (25 km E Te Anau; 45°32.5'S, 167°53.2'E; 295 m), 25 Jan 2004, W. N. Mathis (10♂, 2♀; USNM) . SL : Riverton (46°22.0'S, 168°01.2'E; beach), 14 Jan 2004, W. N. Mathis (5♂, 6♀; USNM); Te Waewae (46°12.3'S, 167°38.1'E; gravel quarry), 19 Jan 2004, W. N. Mathis (2♂, 2♀; USNM) .

OFFSHORE ISLANDS. Chatham Islands. Chatham Island: Manukau (44°01.9'S, 176°20.2'W), 2 Jan 1924, C. Lindsay (1♀; paratype; NZAC) ; Manukau Point (44°02'S, 176°20.2'W), 13 Oct 2002, D. and W. N. Mathis (2♂, 2♀; USNM) ; Ocean Mail Point (2.5 km W; beach on lagoon; 43°45'S, 176°27.6'W), 12 Oct 2002, D. and W. N. Mathis (18♂, 6♀; USNM) ; Owenga (44°01.5'S, 176°21.6'W), 2 Jan 1924, C. Lindsay (1♀; paratype; NZAC) ; Tennants Lake (43°49.4'S, 176°34'W), 14 Oct 2002, D. and W. N. Mathis (1♂, 2♀; USNM) ; Te One Creek (44°01.2'S, 176°23'W), 13 Oct 2002, D. and W. N. Mathis (2♂, 2♀; USNM) ; Tuku River (mouth; 44°03.9'S, 176°39.2'W), 13 Oct 2002, D. and W. N. Mathis (1♀; USNM) ; Waikato Point (beach; 43°50.4'S, 176°30.6'W), 12 Oct 2002, D. and W. N. Mathis (1♀; USNM) ; Wharekauri (43°42.6'S, 176°35.05'W), 12 Oct–16 Jan 1923, 1976, C. Lindsay, R. P. Macfarlane (17♂ (2 paratypes), 18♀ (3 paratypes); NZAC, USNM) . Mangere Island : (44°16.2'S, 176°17.7'W), 4–21 Jan 1924, D. Lindsay (1♀; AMNZ; paratype) . Stewart Island (47°S, 167°50.4'E): 16–22 Feb 1970, R. S. Halligan (3♂, 1♀; LUNZ) .

Distribution ( Fig. 9 ).—Australasian/Oceanian: New Zealand (AK, CL, DN, KA, MC, NC, ND, NN, OL, SL, TO, WI, WN, WO, Chatham Islands, Stewart Island).

Remarks.—This species is distinguished from congeners from New Zealand, especially E. bicolor , which also occurs on Chatham Islands, by the following combination of characters: facial protrusion or hump unicolorous; mesonotum mostly dull, tannish brown to brown with distinctive gray area laterally from postpronotum through the notopleural area; legs blackish brown, including basitarsomeres; surstylus slender and shorter, length less than height of epandrium.

Figures

FIGURES 1–3. Anatomical structures of Ephydrella assimilis (Tonnoir & Malloch). 1. Cibarium, posterior view. 2. Female ventral receptacle, posterior view. 3. Same, lateral view. Scale bar = 0.05 mm.

FIGURES 4–9. Male terminalia and distribution maps of Ephydrella. 4–7. Male terminalia of E. aquaria (Hutton) (specimens from New Zealand Danseys Pass, 12 Jan 2004, W. N. Mathis). 4. External structures, posterior view. 5. Same, lateral view. 6. Internal structures, ventral view. 7. Same, lateral view. Scale bar = 0.1 mm. 8–9. Distribution maps. 8. E. aquaria (Hutton). 9. E. assimilis (Tonnoir and Malloch).

FIGURES 10–12. Head and thorax of Ephydrella assimilis (Tonnoir & Malloch). 10. Latero-oblique view. 11. Lateral view. 12. Dorsal view. Scale bar = 0.5 mm.

FIGURES 13–16. Male terminalia of Ephydrella assimilis (Tonnoir & Malloch; specimens from New Zealand. Waima River, 8 Jan 1994, W. N. Mathis). 13. External structures, posterior view. 14. Same, lateral view. 15. Internal structures, ventral view. 16. Same, lateral view. Scale bar = 0.1 mm.