Silba ischnopoda, Macgowan & Compton, 2018

Macgowan, Iain & Compton, Stephen G., 2018, A new species of Silba (Diptera; Lonchaeidae) associated with figs, Zootaxa 4455 (1), pp. 196-200 : 197-199

Silba ischnopoda sp. nov.

( Figure 1 )

Description. Male: Head: Eyes bare. Frons subshining black, ratio of width to width of an eye 1:2.1, covered in light grey pollinosity. Frontal and interfrontal setulae extremely short, a few longer ones present on anterior margin above the lunule. Orbital plate shining black, bare apart from the orbital seta. Antennae; pedicel brownish-orange medially, postpedicel broadly orange on medial base, this colouration extending along the ventral margin, length to depth ratio 2.6:1. Arista short plumose, ratio of width of plumosity at maximum extent to depth of postpedicel 0.47:1. Lunule setulose, ground colour black, covered with intense silver pollinosity. Face and parafacials lightly silver pollinose. Anterior genal setulae in a single row of 5–6 along the mouth margin, the basal of these the strongest setulae on the genae.

Thorax. scutum and sclerites sub-shining black, lightly covered with grey pollinosity. Scutum covered with short setulae approximately 0.25x length of orbital setae. Anepisternum with a vertical row of 3 anterior setae, 3 strong posterior setae, a single weaker seta lying ventral to these, between these rows a covering of setulae no more than 0.5x length of the setae. Katepisternum with one strong seta close to dorsal margin, a few short setulae anteriorly. Proepisternum with 1 long seta 2x as long as the single seta on the proepimeron. Scutellum; disc slightly brassy in colour, contrasting with the blue-black of the thoracic scutum. Margin, between lateral and apical setae, with 3 short setulae on each side, 2 setulae between apical setae. Calypteres white with a white fringe. Wings clear, veins slightly yellowish, wing length 3.1mm.

Male terminalia: ( Figs. 2–5 ). In lateral view epandrium as wide as high, with a scattering of long, strong setae ventrally. Cerci relatively large and rather rectangular, densely setulose on ventral margin, less so over remainder. Surstylus projecting beyond shell of epandrium as a small rounded posteroventral process. Inner surface of surstylus with a posterior-anterior row of 6 small, black prensisetae, anterior to these and in the same orientation, two small spicules. One strong setae present at the base of each cercus. The area between the row of prensisetae and the ventral margin densely covered in fine setulae. 5 parallel dorsoventral creases on the surface of the surstylus dorsal to the row of prensisetae. Pregonites setulose for most of their length, postgonites rather square shaped with an apical seta. Phallus; U-shaped, basally rather broad, apically a fine slightly curved tube. A pair of lateral, ventrally directed processes arising from the basal section, the apices of these developed into numerous spike-like processes.

Female: In most aspects as in male; frons; ratio of width to width of an eye 1:1.5. Aculeus with apical segment diamond-shaped, numerous short ventral setulae apically.

Type material. Holotype ♂: THAILAND; Songkla province, Ton Nga Chang Wildlife Sanctuary, collected as larva 30.i.2017, eclosed February 2017. S.G. Compton. ( NMS). Reared from figs of Ficus ischnopoda Miquel, 1867 .

Paratypes. 1 ♂, 3 ♀ with the same data as the holotype ( NMS). CAMBODIA; Koh Kong province, Koh Kong env.11’6’’N, 103’0’’E, 28.xi–4.xii. 2010, N. Vikhrev . 1 ♂. (ZMMU)

Etymology. the specific epithet derived from Ficus ischnopoda from the figs of which the larvae were collected.

Differential diagnosis: With only one katepisternal seta, reduced aristal plumosity and a phallus with long lateral processes, S. ischnopoda shows most similarity to two other species which have been reared from figs, Silba lashker MacGowan & Razak, 2012 and S. ishigaki MacGowan & Okamoto, 2013 . These two species are easily distinguished from S. ischnopoda by reference to the shape, particularly at the apex, of the lateral processes of the phallus. In the former the lateral processes of the phallus are smooth and pointed apically, in the latter the lateral processes are bifurcated with one limb being much longer than the other.

Of the other Silba species known to utilise figs as a larval substrate S. inubiwa MacGowan & Okamoto, 2013 also has a single seta on the katepisternum but the phallus is simple with no lateral processes. Silba japonica MacGowan & Okamoto, 2013 and Silba adipata both have two strong setae near the dorsal margin of the katepisternum and in addition S. adipata has a long plumed arista.

Figures

FIGURE 1. Silba ischnopoda sp. nov. Adult, Paratype ♂

FIGURES 2–5. Silba ischnopoda sp. nov. Male terminalia 2. Epandrium and associated structures lateral view. 3. Same, ventral view. 4. Internal view of inner surface of surstylus. 5. Phallus, lateral view.