Silba togoensis, Macgowan & Tschirnhaus, 2024

Macgowan, Iain & Tschirnhaus, Michael Von, 2024, Records of Lonchaeidae (Diptera, Cyclorrhapha) from Togo and other African countries, with descriptions of new species, Zootaxa 5514 (1), pp. 1-27 : 11-12

Silba togoensis sp. nov. ( Figures 28–30 )

Description: Holotype male: Head: Eye bare. Ratio of eye width to frons width 1.5:1 Frons sub-shining black, dulled by microsculpture. Orbital plate sub-shining black, dulled by microsculpture, bare apart from the orbital seta. Frontal and interfrontal setulae short, at most 0.2x length of orbital seta, Lunule covered in dense greyish pollinosity, parafacial slightly grey pollinose, face black. Antenna, postpedicel brownish-black, long, reaching down below mouth margin, length to depth ratio 2.8:1. Arista yellowish basally, width of plumosity approximately 0.5x depth of the postpedicel. Anterior genal setulae in a single row of 5–6 along mouth margin. Palpus black.

Thorax: Mesonotum sub-shining blue-black, with a covering of short setulae, these approximately 0.25x length of the orbital seta. Anepisternum with a vertical row of three posterior and three anterior setae, otherwise the sclerite with a scattering of setulae. One seta on proepimeron and one slightly weaker on proepisternum. Katepisternum with two setae near the dorsal margin, the posterior slightly stronger and positioned slightly more dorsal than the anterior, a scattering of short setulae located along the anterior margin of this sclerite otherwise the surface is bare. Scutellum with setae and setulae mostly missing. Calypter whitish with a short, white fringe of uniform length. Wing clear with pale brown veins, wing length 3.9mm. Haltere dark. Legs entirely dark.

Male terminalia: In lateral view epandrium almost twice as high as wide, with strong setae on posterior half, the longest and strongest of these near the posterior margin reaching to apex of the cercus. In ventral view surstyli covered in minute spicules, inner margin with some five excavations, these becoming smaller anteriorly. Inner margin of surstylus with five prensisetae along posterior margin, the most posterior being the largest, the most anterior the smallest and slightly detached from the remainder. Phallus clearly bi-segmented, the basiphallus being a relatively deep boat-shape, 0.3x as deep as it is long with obvious spicules on the apical half, distiphallus length equals length of the basiphallus, distiphallus slightly expanding apically, apex oblique with a membranous tip.

Diagnosis. This is a member of the Silba adipata species-group exhibiting the serrated inner margin of the surstylus. However, in the case of S. togoensis the rather stout phallus with obvious spicules on the apical half of the basiphallus is distinctive. Silba adipata is similar but the corrugations of the inner surface of the surstylus are smaller and more regular. The phallus is longer and more slender, the distiphallus being 1.4x the length of the basiphallus and the basiphallus 0.2x as deep as it is long. Differences from Silba otandjobo are outlined in the key.

Type material. Holotype: ♂. TOGO: Togo Région des Plateaux: N of Kessibo-Wawa, at the border to Ghana (N. of Badou), at river Wawa , 7.7030N 0.5905E, Forest understory, cocoa plantation, and sun exposed vegetable fields, some Cyperaceae , 180m, 24.4.200 8, leg. M. von Tschirnhaus. Specimen deposited in SDEI; SDEI-Dip-01004.

Etymology. The specific epithet refers to Togo.

Figures

FIGURES 28–30. Silba togoensis sp. nov. 28. Epandrium and associated structures, lateral view (hypopygium removed). 29. Inner surface of surstylus. 30. Phallus, lateral view.