Silba apodesma

Description: Fairly small; length 3.5 mm. Sinning blue-black; bluish reflections
distinct but rather subdued. One of the few Silba species with partly pale tarsi.
Male.—Head, in front views, widely oval (11.0:9.0). Compound eye bare. Frons
subshining black; approximately as wide at lunule as at anterior ocellus; narrower
in middle; hairs rather fine and sparse, those immediately above lunule stronger.
'I Orbital plate bare above orbital bristle. Orbital and inner vertical bristles subequal
0 in length and strength; slightly finer than ocellar bristle. Outer vertical bristle
scarcely more than half as strong as inner vertical. Post-ocular setulae short and
closely spaced. Lunule orange-brown; small; with three or four setulae on each side.
Parafacial narrow but not linear; lightly silvery pollinose. Face gently convex in
middle; almost flat at mouth margin. Cheek very narrow in lateral view; in ventral
view, shortest distance from mouth-margin to compound eye approximately as
wide as third antennal segment. Third antennal segment dark brown except at
extreme inner base; more than three times as long as wide (7.0:2.2); slightly con¬
stricted just beyond middle. First and second antennal segments dark brown; dorsal
bristle of second segmexit distinctly weaker than the outer vertical bristle. Arista
yellowish on basal one-third; greatest width of plumosity about three-fourths width
of third antennal segment.  Thorax black with blue-black reflections. Mesonotum fairly shiny; hairs short,
ine and depressed; bristles fairly strong. Scutellum moderately heavily coated with
veakly iridescent pollen; each side with three lateral setulae in addition to usual
¦cutellar bristles; apex bare. Mesopleuron hairy; with three strong posterior bristles
md two or three weaker anterodorsal bristles. Sternopleuron with two bristles and
'ew fine hairs. Stigmatal and propleural bristles single; very fine. Prosternum with
,hree or four fine hairs on each side.
Wing membrane clear; slightly whitish in reflected light; veins pale yellow. Calyp-
-,rae white, with pale margins and fringes. Legs black. All metatarsi yellow; following
segments progressively darker brown.
Abdomen shining blue-black in posterodorsal views; in anterodorsal views,
h Lctly dull greyish pollinose; approximately one and one-fourth times as long as
wide (14.0:11.0); last apparent tergum as long as preceding two terga.
Genitalia (Figs. 86, 87, 88)~m£ffek)ngate, fused cerci and large strongly sclerotized
pregonite; aedeagus bilobate; ventral lobe larger, bifurcate at apex, partially enveloping the finger-like intromittent organ