Silba setigonite
Description: Male. Head: Eyes bare. Frons sub-shining black, dulled by microsculpture,
frontal and interfrontal setulae very short, at most 0.2× length of orbital
seta, longer on anterior margin above lunule. Lunule with brownish ground colour,
when seen from above moderately silver pollinose as are parafacials and face.
Anterior
genal setulae in a single row of 7–8 along mouth margin, decreasing in
length anteriorly. Antennae, postpedicel black apart from a small orange area at
extreme
medial base, length to depth ratio 2.8:1. Arista plumose, ratio of plumosity
at maximum extent to depth of postpedicel 1.1:1.
Thorax: Scutum shining blue-black contrasting with the rather matt grey-black
scutellar dorsum. Anepisternum with four anterior setae and four posterior setae,
remainder of sclerite covered in rather sparse, long setulae. Katepisternum with two
setae located near dorsal margin, anterior being slightly shorter and weaker than
posterior. Scutellum, on margin between lateral and apical setae, with three setulae
on each side, none between apical setae. Calypteres pale, with a pale margin and
fringe. Wings clear, veins brownish, wing length 4.0 mm. All femora and tibiae dark
brown, contrasting with dark setulae and setae, tarsomeres dark.
Male terminalia: In lateral view epandrium of unusual shape, with moderately
large rectangular process posteriorly behind which one of strong prensisetae
projects, a row of very long setulae present along posterior and ventral margins.
Cerci relatively small, slightly rectangular in shape, bearing numerous short setulae.
Surstyli extending beyond shell of epandrium posteroventrally as large semicircular
lobe. Inner surface of surstyli with two prensisetae, a smaller, medially directed
posterior prensiseta located just below base of cerci. A much larger ventral prensiseta
directed ventrally, extending beyond outer margin of surstylus, otherwise inner
surface
with only a few small setulae near ventral margin. Pregonite, moderately
large, simple processes, pointed at apex, covered in numerous short setulae. Postgonite,
relatively small with short marginal fringe of setulae. Phallus relatively
simple, slightly angular, J-shaped tube without ornamentation apart from area of
small scales medially.
Figs 18–21: Silba setigonite n. sp.: (18) epandrium and associated structures, lateral view; (19) same,
ventral view; (20) surstylus, inner surface; (21) phallus, lateral view. Scale 0.1 mm.
21