Silba microcercosa, Introduction & Fallén & Morge, 2007

Introduction, Iain, Fallén, Lonchaea & Morge, Setisquamalonchaea, 2007, New pecies of Lonchaeidae (Diptera: Schizophora) from Asia, Zootaxa 1631, pp. 1-32 : 26

Silba microcercosa sp. nov.

The holotype is in poor condition with three legs missing and the majority of the strong setae of the head, thorax and scutellum either missing or broken.

Description. Holotype male: Head: Eyes bare. Frons narrowing slightly ventral to the ocellar triangle then parallel sided, widening out slightly just dorsal of the lunule; subshining; with two central, raised, parallel ridges running from anterior margin to a point half way towards the anterior ocellus; bearing short frontal and interfrontal setulae less than one quarter length of orbital setae, longer setulae on anterior margin above lunule. Orbital plates long and narrow; subshining and covered in fine microsculpture; bare apart from orbital setae. Lunule with orange brown ground colour, covered with slight silver dusting, two setulae present on one side and one on the other. The orange brown colour of the lunule extending ventrally over entire face and along mouth edge below level of anterior genal setae; face centrally with a golden metallic lustre. Anterior genal setulae extending as a single row of four or five along mouth edge, these not noticeable stronger than other setulae on the genae, Antennae with first and second segments orange brown, antennal flagellomere also orange brown but slightly darker dorsally and apically; two and a half times as long as deep, just reaching the mouth edge. Arista with plumosity at its greatest extent approximately as wide as depth of antennal flagellomere.

Thorax: Disc, pleurae and scutellum all rather heavily dusted. Anepisternum, with three strong setae anteriorly and four posteriorly. Katepisternum with two strong setae, posterior one stronger and situated slightly dorsal to anterior; approximately twelve setulae on anterior part of sclerite, those immediately anterior to the anterior setae relatively long. One propleural and one thinner stigmatical setae. Scutellum on margin with one setulae on each side between apical and lateral setae, but, others may be missing. Squamae pale yellow with a pale fringe. Wings with a slight yellow tinge. Wing length 4.0 mm. Legs: Femora and tibiae black, posterior leg with basal tarsomere mainly dark but apically yellow brown, apical tarsomeres orange-brown, middle leg with tarsomere colour similar but darker, anterior legs missing.

Male terminalia: Figs. 56–59. Epandrium rather globular, in lateral view rounded posteriorly, ventrally and anteriorly but rather angular dorsally, moderately long and dense setulae present posteroventrally, longest setulae present along the ventral margin, otherwise bare. Cerci forming a rather small finger-like process, height less than half of epandrium, apically covered in setulae longer on dorsal margin. In ventral view surstyli visible as a pair of rounded lobes bearing eight to nine small black spinules, these lobes not extending beyond shell of epandrium. Sub-basal plate with five moderately sized black teeth, two downward pointing spinules present below the base of the cerci. Aedeagus a complex structure, on each side of slender central apical shaft there is an outer long lateral process which reaches up past the apex of the central shaft, this lateral process is club shaped at its apex and half way along its length is a small inner branch with an irregular apex. At the base of the central shaft is a smaller finger like forward pointing process.

Differential diagnosis: The unique male terminalia readily distinguish this species from other Asian Silba species.

TYPE MATERIAL: Holotype male. VIETNAM: Nui Ba Den ( Black Virgin Mountains ) Tay Ninh Province, 3200ft, 6–8 viii 1970, leg. A. R. Gillogly.

Only known from the holotype in the AMS.

Etymology. The specific epithet is derived from the relatively small cerci of the male terminalia.