Silba namibia
The combination of partly yellow tarsomeres, tall epandrium
and cerci and surstyli with teeth exposed on the margin show that S.namibia belongs to the
group of species which includes S. admirabilis McAlpine,1956, S. apodesma McAlpine,
1960 and S. pappi, Soós 1977. Within the African species of Silba this species is comparable
at present only to S. apodesma. S. namibia is similar in many respects to S. apodesma
sharing the yellow basal tarsomeres and the broad female ovipositor. It clearly differs,
however, in characters of the male genitalia, in particular the aedeagus.
S. namibia differs from the closely related S. apodesma by the following character
states: the orbital plate bears only the orbital bristle with no additional hair or hairs being
present, the lunule and face have a silvery tomentum, in S. apodesma the lunule is orangebrown,
in S. namibia sp. nov. the length of the plumosity on the arista is approximately
equal to the depth of the first flagellomere, whilst in S. apodesma the length is approximately
only three quarters the depth of the first flagellomere.
Description. Male: Head: Eyes bare. Frons half the width of an eye, narrowest point at
level of top of lunule, widening very slightly above and below this point. Frons covered in
rather short dark hairs, the majority of those on the upper and mid frons only one third the
length of the orbital bristle, a few longer hairs just above the lunule, these half the length
of the orbital bristle. Lunule with four setulae, two on each side. Orbital plates shining, no
hairs present above the orbital bristle. Antennae entirelly black; first flagellomere long,
three times as long as deep and just reaching past the mouth edge.
Arista with plumosity just slightly wider than the first flagellomere. Lunule, parafacials
and face all silver pollinose. A single row of five to six anterior genal bristles extend ing in a single row along the mouth edge, none of these significantly stronger or longer ZOOTAXA
than any of the others. Genae relatively narrow only slightly wider than the depth of the
first antennal flagellomere. Thorax: one propleural and one stigmatical bristle. Prothoracic episternum haired.
Two pairs of dorsocentral bristles, one pair of acrostichals situated near posterior margin
of thoracic dorsum. Two strong katepisternal bristles, anterior one slightly weaker than the
posterior, no hairs present below or behind them, this sclerite otherwise bare apart from six
to eight hairs on the upper anterior corner. Anepisternum with three strong anterior and
two strong posterior bristles. Thoracic dorsum with rather short coarse hairs these at most
half the length of the orbital bristle. Scutellum with disc pollinose contrasting with the
shining black thoracic dorsum. Scutellum with four to five hairs between lateral and apical
scutellar bristles, no hairs between the apical bristles. Lateral bristles much nearer the base
of the scutellum than they are to the apical brisltes.
Squamae including margins and fringes golden yellow. Wing with crossvein R-M
occurring before the level of the intercostal space, wings slightly fumose. Wing length
4.0mm.
Legs black but basal tarsomeres golden brown, other tarsomeres becoming progressively
darker .
Male genitalia: Fig.4; 1,2,3,4. Epandrium one and a half times higher than it is broad,
bearing a series of long hairs along its ventral margin. Cerci tall and narrow, slightly more
than half as tall as the epandrium, bearing short hairs ventrally and posteriorly. In ventral
view epandrium with eight strong black teeth exposed on ventral margin. Pregonites long
and tall with curved apices. Aedeagus bilobate with a larger ventral lobe partially enveloping
the finger like inner process. The ventral lobe is relatively broad and only slightly
excavated at the apex, the apical margin bearing a few spicules, a few spicules also present
on the basal part of the ventral lobe. The inner process is subequal in size and length to the
ventral lobe.
Female with usual sexual differences; frons about as wide as an eye.