Parahyadina debilis, Mathis & Zatwarnicki, 2019

Mathis, Wayne N. & Zatwarnicki, Tadeusz, 2019, Revision of the Shore-fly Genera Parahyadina Tonnoir and Malloch and New Zealand Hyadina Haliday (Diptera: Ephydridae), Zootaxa 4623 (3), pp. 401-440 : 420-421

Parahyadina debilis , sp. nov.

( Figs. 27 , 29–32 , Map 6 )

Diagnosis. This species is distinguished from congeners by the following combination of characters: Adults. Small shore flies, body length 1.45–1.75 mm.

Head ( Fig. 27 ): Lateroclinate fronto-orbital seta well developed, basal diameter comparable or only slightly reduced in comparison to basal diameters of vertical setae.

Thorax ( Fig. 27 ): Postsutural scutum with distinct, longitudinal vittae in rows between acrostichal setae and dorsocentral setae; 2 pairs of posterior dorsocentral setae, anterior seta shorter than posterior seta. Wing hyaline; costal section II shorter in length than costal section III; costal vein ratio 1.00–1.20; M vein ratio 0.28–0.31.

Abdomen: Tergites 3–5 with ventrolateral margin shallowly and bluntly rounded; male tergite 5 extended posteriorly in same plane as tergite 4. Male terminalia ( Figs. 29–32 ): Epandrium in posterior view ( Fig. 29 ) an inverted U-shaped structure, lateral margins only slightly oriented medially, surstylus in posterior view ( Fig. 29 ) subrectangular, ventral margin emarginated medially, shallowly bifurcate, lateral extension of bifurcation longer than medial extension or bump, surstylus bearing 7–8 longer setulae on ventral portion and with an apical, prominent setula, in lateral view ( Fig. 30 ) with epandrium very narrow and straight, surstyli expanded, irregularly, row of 7–8 subapical setulae and an apical setulae; cercus in posterior view ( Fig. 29 ) irregularly oblanceolate, pointed tapered to narrowly rounded point dorsally, ventral margin broadly rounded, in lateral view ( Fig. 30 ) irregularly semihemispherical, height almost twice width, dorsal margin rounded, posterior margin tapered to rounded point, generally covered with small setulae; aedeagus in lateral view ( Fig. 32 ) comparatively small, length more than half that of phallapodeme, anterior margin broadly rounded, posterior margin with a medial, narrow, process, in ventral view ( Fig. 31 ) with large base somewhat rectangular, basal margin concave and apical margin abruptly narrowed to medial, pointed process; phallapodeme in lateral view ( Fig. 32 ) elongate, moderately narrow, base with short, anteriorly directed projection, just beyond midlength with a robust, large projection, thereafter tapered slightly to narrowly truncate apex, in ventral view ( Fig. 31 ) as an inverted Y with bifurcate base and narrow, elongate extension to pointed apex; gonite and hypandrium broadly fused, in lateral view ( Fig. 32 ) robustly L-shaped, gonal portion shorter than hypandrial portion and deeply bifurcate medially, margins nearly straight, hypandrial portion, narrow, somewhat elongate, in ventral view ( Fig. 31 ) longer than wide, robust with large, basal margin of hypandrium deeply emarginate, forming 2 posterolateral, digitiform processes, gonal portion extended apically as 2 deeply bifurcate processes, lateral prong of gonal apex more robust than shorter, medial process.

Type Specimen. The holotype male is labeled “ NEW ZEALAND. S. Isl. OL: Mararoa River (25 km E Te Anau; 45°32.5’S, 167°53.2’E; 295 m), 25 Jan 2004, Wayne N. Mathis (2♂, 1♀; USNM)/ USNM ENT 00285069 [plastic bar code label]/ HOLOTYPE ♂ Parahyadina debilis Mathis & Zatwarnicki NZAC [red].” The holotype is double mounted (minuten in a plastic block), is in excellent condition, and is deposited in the NZAC. Two paratypes (1♂, 1♀; USNM) bear the same label data as the holotype.

Type locality. New Zealand. South Island. OL: Mararoa River (25 km E Te Anau; 45°32.5’S, 167°53.2’E; 295 m) .

Other specimens examined. SOUTH ISLAND. DN: Otago Peninsula , Hoopers Inlet (45°51.1’S, 170°39.7’E); 13 Jan 2004, W. N. Mathis (1♂; USNM).

Distribution ( Map 6 ). Australasian/Oceanian: New Zealand. South Island (DN, OL).

Etymology. The species epithet, debilis , is of Latin derivation and means weak, referring to the weakly developed fronto-orbital seta of this species.

Remarks. This species is similar to P. latistylis in having shortened and apically developed surstyli. Details of the apical portion of the surstylus differ as seen by comparing Figs. 29–30 (this species) with Figs. 55–56 ( P. latistylis ). The gonites differ considerably and readily distinguish this species, especially the anterior extensions, which are conspicuously bifurcated and each process is oriented anteriorly. This homologous structure in P. latistylis is flared laterally, tapered, and projected as a single process.

Figures

MAP 6. Parahyadina debilis.

FIGURES 27–28. Antero-oblique photo of head and thorax (Scale bar = 0.2 mm). 27. Parahyadina debilis sp. nov. (female; New Zealand. South Island. OL: Mararoa River). 28. Parahyadina edmistoni sp. nov. (female; New Zealand. North Island. ND: Hailes Road).

FIGURES 29–32. Parahyadina debilis sp. nov. (male; New Zealand. South Island. OL: Mararoa River (25 km E Te Anau)). 29. Epandrium, cerci, and surstyli, posterior view. 30. Same, lateral view. 31. Internal structures of male terminalia, ventral view. 32. Same, lateral view (scale bar = 0.1 mm).

FIGURES 55–58. Parahyadina latistylis sp. nov. (male; New Zealand. North Island. TO: Tokaanu). 55. Epandrium, cerci, and surstyli, posterior view. 56. Same, lateral view. 57. Internal structures of male terminalia, ventral view. 58. Same, lateral view (scale bar = 0.1 mm).