Differential diagnosis: The epandrium with an obvious 9th tergite is apparently
unique amongst the described species of Silba. This tergite is evident in Lonchaea
species in the Lonchaea polyhamata McAlpine, 1964 species-group (MacGowan
2018) and all known Fulgenta species and may well represent a primitive condition
within the family. The row of three closely situated rounded prensisetae, the asymmetrical
pregonites with the left being very long and chitinised and the unique
serve to distinguish this species from other Silba species.
Description: Male. Head: Eyes bare. Frons sub-shining black, frontal and interfrontal
setulae very short, approximately 0.15× length of orbital seta. Lunule, base colour
black, when viewed from above covered with moderately dense silver pollinosity,this extending onto parafacials and face. Anterior genal setulae in a single row
along mouth margin, none of these particularly strong. Antennae black, postpedicel
orange at extreme medial base, length to depth ratio 2.5:1. Arista plumose, ratio of
plumosity at maximum extent to depth of postpedicel 1:1.
Thorax: Scutum shining blue-black. Anepisternum with three anterior and three
posterior setae. Katepisternum with two setae located near dorsal margin, anterior
only slightly shorter and weaker than posterior. Scutellum, on margin between lateral
and apical setae, with five multiserial setulae on right, two on left, two very
short setulae between apical setae. Calypteres pale, with golden margin and fringe.
Wings slightly fumose anteriorly, veins brownish, wing length 4.5 mm. All femora
and tibiae dark brown, contrasting with the dark setulae and setae (this may be age
related fading) tarsomeres entirely black.
Male terminalia: Epandrium with 9th and 10th tergites not completely fused, 9th
a rounded lobe, thin and lightly sclerotized, attached to anterior surface of
10th tergite, 10th tergite spherical, bearing numerous rather short setulae on ventral
margins. Cerci relatively small, bearing numerous short setulae. Surstyli contained
within shell of epandrium, with a multiple row of short setulae along ventral margin.
Inner surface of surstylus with almost fused row of three rounded prensisetae
situated below base of cerci, strong inwardly pointing seta arising from near base
of prensisetae, loose row of setulae lying anterior to them. Left pregonite
enlarged and sclerotized, forming long, black pointed projection, right pregonite
insignificant. Postgonites large and sclerotized. Phallus large open U-shaped, simple
basally, on apical third with two long, slender processes, one longer than apex of
phallus, other shorter, apex of phallus ribbon-like with numerous small setulae on
shaft and especially at apex.