Silba hebridensis, MacGowan, 2021

Macgowan, Iain, 2021, The Lonchaeidae of Vanuatu (Diptera: Schizophora), Zootaxa 4926 (3), pp. 342-362 : 358

Silba hebridensis sp. nov. ( Figures 36-39 )

Description. MALE: Body length 3.0mm.

Head: Eyes bare. Frons when viewed from above grey dusted, ratio of width at anterior margin to eye width 0.5:1. Interfrontal and frontal setulae very short approximately 0.1x length of orbital seta, becoming longer near anterior margin. Orbital plate shining black, bare apart from orbital seta. Lunule, ground colour dull brown, lightly grey dusted as are face and parafacials. Antennae entirely black, postpedicel length to depth ratio 1.9:1. Arista plumose, ratio of plumosity at maximum extent to depth of postpedicel 1.1:1. Anterior genal setae in a single row of five along mouth margin.

Thorax: scutum shining black, covered with setulae approximately 0.25x length of orbital seta. Anepisternum with three anterior and four? posterior setae. Katepisternum, two setae located near dorsal margin, anterior weaker than posterior. One seta on both proepimeron and proepisternum. Scutellum, disc heavily dusted, bare, margin between lateral and apical setae with three setulae on left side, two on right, one setula between apical setae. Calypteres white with a white fringe. Wings light fumose, veins light brown. Wing length 2.8mm. Legs entirely black.

Male terminalia: In lateral view epandrium slightly wider than high, in ventral view rather spherical, long setae situated along posterior and ventral margins. Cerci rather rectangular approximately 0.5x height of epandrium, with numerous setae apically Surstyli projecting beyond shell of epandrium ventrally as a blunt, almost square process. Internal surface of surstyli with a posterior uniserial row of 6 uniformly sized prensisetae, two strong setae situated near base of cerci. Remainder of inner surface covered with numerous small spicules ventrally, medially with an anterior-posterior loose row of small tubercles. Four—five strong setae located at base of posterior process. Pregonites rather large and club-shaped. Phallus, a complex structure, consisting of closely associated outer and inner layers, inner section C- shaped with a rather acutely pointed apical part, a small lateral projection present at base of apical half. Outer layer following the curvature of the inner but straighter and blunter apically.

Type material. Holotype ♂: VANUATU: Malekula , Oubua, iii & iv.1929, L. E. Cheesman ( BMNH).

Paratype: 1 ♂ with the same data as holotype.

Etymology. The specific epithet refers to the New Hebrides, the pre-independence name of Vanuatu.

Remarks. A relatively dull and dusted species. In the general shape of the epandrium it shows some affinities to S. erromango described above but there are fewer prensisetae. It also lacks the numerous processes arising from the hypandrial structures and the phallus is more complex. The Holotype is mounted on a rather large pin which has somewhat squashed the specimen.

Figures

FIGURES 36-39. Silba hebridensis sp. nov. 36. Epandrium and associated structures, ventral view. 37. Surstylus, internal view. 38. Phallus and parameres lateral view. 39. Phallus, parameres and postgonites, ventral view.