Silba erromango, MacGowan, 2021

Macgowan, Iain, 2021, The Lonchaeidae of Vanuatu (Diptera: Schizophora), Zootaxa 4926 (3), pp. 342-362 : 355-357

Silba erromango sp. nov. ( Figures 33—35 )

Description. MALE: Body length 3.0mm.

Head: Eyes bare. Frons dull sooty black, narrowing only slightly from level of ocellar triangle to antennal bases where it is 0.5x eye width. Interfrontal and frontal setulae approximately 0.25x length of orbital seta, becoming longer near anterior margin. Lunule black, face and parafacials light grey dusted Antennae black, postpedicel length to depth ratio 1.7:1. Arista missing. Anterior genal setulae in a single row of four along mouth edge, the basal setula of this row strong and reclinate.

Thorax: scutum sub-shining blue black, covered with setulae approximately 0.25x length of orbital seta. Anepisternum with two? anterior setae and three? posteriorly (these difficult to distinguish from other long setulae on the sclerite). Katepisternum, one strong seta situated near dorsal margin, a weaker seta situated anterior to it. Scutellum with setae and setulae missing. Calypteres; very small, greyish with a darker margin, fringe short and dark. Wings light fumose, wing length 2.8mm. Legs entirely black.

Male terminalia: In lateral view epandrium slightly wider than high, in ventral view rather spherical, with a scattering of long setae along posterior and ventral margins. Cerci rather rectangular approximately 0.5x height of epandrium. Apically with numerous setae approximately 0.5x as long as depth of cerci. Surstyli projecting beyond shell of epandrium ventrally, forming a relatively large finger-like posterior projection. Internal surface of surstyli posteriorly with a row of eight prensisetae gradually decreasing in size ventrally, a ninth smaller prensiseta slightly detached at ventral end of the row. one strong seta situated anterior to dorsal two prensisetae, remainder of inner surface with numerous small setulae. Approximately seven setae located at base of the finger-like process. Hypandrium conspicuous for its numerous projections, two long, sinuous ventrally- directed finger-like projections arising from anterior margin of hypandrial apodeme, a shorter pair situated laterally to these. Pregonites with long apical projections each bearing a single seta, with an additional long, curved posterior arm. Postgonites also extended ventrally into two arms, setulose at apices. One further pair of long medially-directed projections arising near posterior margin of hypandrium. Phallus; a simple J-shaped tube.

Type material. Holotype ♂: VANUATU: Erromango , Dillons Bay, iii.1981, N. L. H. Krauss ( BMNH).

Paratypes: Tanna, Lenakel. 0-150m, iii 1970, N. L. H. Krauss, 6♂; Lenakel. 0-100m, xi 1978, N. L. H. Krauss, 1♂ ( BPBM).

Etymology. The specific epithet refers to the island of Erromango on which the holotype was captured.

Remarks. This species is distinguished from other Silba species by its numerous short prensisetae and the unique ventrally-directed projections arising from the structures of the hypandrium.

Figures

FIGURES 33-35. Silba erromango sp. nov. 33. Epandrium and associated structures, ventral view. 34 same, lateral view. 35. Surstylus, internal view.