Silba trigena MacGowan, 2004

DESCRIPTION :  Male : Head ;  Eyes bare. Frons about half the width of an eye, flat and moderately pollinose. Orbital plate bare, shining and extending half way between the eye margin and the anterior ocellus. Hairs on the upper part of the frons very short, not more than one quarter the length of the orbital bristle, a row of six to seven longer ones at the anterior margin of the frons just above the lunule. Lunule, face and parafacials moderately silvered when seen from above, lunule with four long hairs on one side and five on the other, these as long as the long hairs on the anterior margin of the frons. Sub vibrissal hairs extending as a single row anteriorly this consisting of six to seven hairs, the basal three of these amongst the strongest hairs on the jowls but not noticeably stronger than the rest. Jowls relatively narrow, narrower than the depth of the first antennal flagellomere. First antennal flagellomere two and a half times as long as it is deep, reaching down over the mouth margin, all black apart from being very obscurely dark brown at the base internally, slightly constricted in apical half and upturned towards the apex. Arista yellowish on basal third, plumosity at its maximum extent as wide as the depth of the flagellomere.

Thorax:  Hairs on the thoracic disc short, about one quarter as long as the orbital bristle. All pleurae dusted as is the scutellar disc and the hind margin of the thoracic disc. One propleural and one stigmatical bristle. Anepisternum with two strong bristles anteriorly and three posteriorly. Katepisternum with the usual two strong bristles, no hairs present posterior to or below these, anterior bristle only very slightly weaker than the posterior one, the other hairs on the anterior part of the katepisternum short, only about one quarter as long as the strong bristles.  Scutellar margin between lateral and apical bristles with one hair on one side and two hairs on the other otherwise bare, apical scutellar bristles crossed near their apex.

Squammae and squammal fringes white, wings clear with yellow veins. Legs entirelly black, front femur with a row of eight strong bristles posterio ventrally.  Sternite one shining and without hairs, other sternites dusted and setulose.

Male genitalia : Fig 2; 4,5,6,7. Epandrium as high as it is wide, rounded ventrally with a projection anteriorly and a circular excavation dorsally, posterioventraly well covered in hairs but none of these exceptionally long or strong.  Cerci relatively small and simple bearing numerous hairs. In lateral view surstyli not projecting beyond shell of epandrium but in ventral view with obvious rounded lobes which bear a series of regular hairs, otherwise remainder of margin of surstyli bare. Seven small sharp black teeth present on posterior lobe of the surstyli, these extending down on the inner surface of the surstyli, one small tooth present centrally below the base of the cerci.  Aedeagus  in lateral view with two sharp and pointed lateral lobes the same size as the central projection, in ventral view these slightly lobed near the apex and curving out like horns on either side of the central projection, basal portion of aedeagus rather flat and simple.
Female unknown.