Hyadina Haliday, 1837

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 : 404-405

Genus Hyadina Haliday

Hydrina Robineau-Desvoidy 1830: 794 . Type species: Hydrina vernalis Robineau-Desvoidy 1830 (= Notiphila guttata Fallén 1813 ), subsequent designation, Coquillett 1910: 553. Preoccupied ( Rafinesque 1815, Coelenterata).

Hyadina Haliday in Curtis 1837: 282 . [published in synonymy, first used for a taxon by Haliday 1839: 404]. Type species: Notiphila guttata Fallén 1813 , subsequent designation, Westwood 1840: 153.— Loew 1860: 27 [generic status].— Thompson and Mathis 1981: 84 [historic review of the nomenclature].— Mathis and Zatwarnicki 1995: 202–207 [world catalog].

Ephydrosoma Lioy 1864: 1103 . Type species: Ephydra rufipes Meigen 1830 , monotypy.— Mathis and Zatwarnicki 1995: 202 [synonymy].

Diagnosis. Hyadina is distinguished from other genera of the tribe Hyadinini by the following combination of characters: Adults, small to medium-sized shore flies, body length, 1.20–2.70 mm; mostly shiny black, often with dense microtomentum on abdomen; setation generally weakly developed.

Head: Frons bare to densely microtomentose. Face generally paler in than frons, yellow to dark yellowish brown with golden, yellowish silver, or silvery gray microtomentum extended to gena. Gena often concolorous with ventral parafacial plate, sometimes ventral gena bare or with sparse microtomentum. Chaetotaxy: ocellar setae well developed, divergent, proclinate; pseudopostocellar setae minute, divergent, proclinate; fronto-orbital setae, minute, 3–5 pairs, proclinate; medial vertical setae well developed; lateral vertical well developed or reduced; facial setae, minute, in 2 rows. Antenna yellow, yellowish brown, or brown; scape, pedicel, and 1st flagellomere often darker in color dorsally; scape with row of setulae along apicoventral margin; 1st flagellomere microtomentose with numerous setulae; arista bearing very short rays on dorsum. Palpus prominent, yellow to dark yellowish. Gena low to moderately high.

Thorax: Mesonotum bare or with sparse to dense microtomentum, ground color pale brown to dark brown, microtomentum golden, silver, velvety black or brown, often marked with distinct vittae. Scutellum trapezoidal with posterior margin slightly rounded, lateral margins sometimes with dense velvety black patches; pleura often paler than mesonotum; anepisternum bare or with dense microtomentum, often dorsally with black velvety patches; katepisternum bare or with sparse to dense microtomentum. Chaetotaxy: pre and postsutural dorsocentral setae lacking; scutellar and acrostichal setae well developed; 1 prominent supra-alar setae; anterior notopleural setae either well developed, reduced, or lacking; 1 anepisternal seta, small to minute, inserted along posteromedial margin; 1 katepisternal seta, small to minute, inserted along dorsomedial margin; 2 lateral scutellar setae, posterior seta inserted apically, lateral seta 1/3–1/2 length of posterior seta. Wing: hyaline to yellowish brown; crossvein dm-cu often with dark rims and hyaline spots in the surrounding wing areas; rarely with additional stump veins or brownish pattern in wing; costa extended to vein M. Legs: yellow, yellowish brown, to dark brown; covered by rows of minute setulae; femora and tibiae often with pattern of pale and dark areas; apical tarsomere and sometimes tarsomere 4 often darker than proximal tarsomeres. Halter knob white, yellow to yellowish brown.

Abdomen: Five abdominal tergites normally exposed in males, cerci well developed; abdominal tergites 6–8 normally exposed in females, cerci well developed; generally shiny with sparse microtomentum; ground color yellowish brown, brown to dark brown; partially bare, and usually with distinct areas of sparse to dense microtomentum; tergites setulose, with setal rows along margins. In some species tergites 2 and 3 laterally with separated plates, reaching ventral margin of abdomen. Female without fused sternites. Male terminalia: epandrium often narrow, especially dorsally, lacking setae, separated from cerci; surstylus attached with venter of epandrium, variously shaped, mostly triangular or rounded anteriorly, bearing 1 to several strong setae towards or at anterior margin; cercus semicircular to oval; aedeagus in most species long, slender, bearing posterodorsal process, rarely oval in ventral view, usually conspicuously arched in lateral view; phallapodeme usually long and narrow, rarely triangular in lateral view; gonite fused with hypandrium, rarely bearing anteroventral seta, usually without setae; often arcuately triangular and tapered apically in lateral view; hypandrium shallow, directed perpendicularly [transversely] to gonites.

Discussion. Mathis and Zatwarnicki (2004) discussed and clarified the nomenclatural issues associated with Hyadina and its synonyms. Although Hollmann-Schirrmacher (1998) synonymized Lytogaster with Hyadina , we do not accept the basis for this synonymy (his interpretation of characters of the male terminalia) and do not follow his precedent (Mathis and Zatwarnicki 2004).

The fauna of Hyadina from New Zealand comprises a single, undescribed species, and as noted previously, it is not to be confused with the two endemic species that were initially described in Hyadina . We are placing the latter two species in a separate genus (Mathis & Zatwarnicki, in press).