Stilpon ubinensis, Grootaert & Shamshev, 2015

Grootaert, Patrick & Shamshev, Igor, 2015, New species of fast-running flies (Diptera: Empidoidea, Hybotidae, Tachydromiinae) from mangroves in Singapore, Raffles Bulletin of Zoology 63, pp. 583-609 : 607-608

Stilpon ubinensis , new species

( Figs. 44–47)

Material examined. Holotype male, Singapore, Pulau Ubin (Chek Jawa, type locality): 23 June 2012, PU1 , Malaise trap in mangrove (reg. 29306, Ma7443).

Etymology. The epithet refers to the type locality Pulau Ubin.

Diagnosis. Species with yellow thorax, scutum with brownish yellow patch above wing base; legs entirely yellow; wing distinctly maculate, broadly brownish infuscate along R 2+3 and CuA 1 (except subapical part), haltere with black knob.

Description. Length: body 1.1 mm, wing 1.1 mm.

Male: Head black. Two minute fine vertical bristles present. Frons linear with sides nearly parallel, broad, entirely tomentose. Ocellar tubercle with minute setulae. Antenna with scape and pedicel yellowish brown, postpedicel yellow. Palpus yellow, with moderately long, yellowish subapical bristle.

Thorax yellow in ground-colour; scutum with brownish patch above wing base, scutellum and metanotum brownish yellow, sutures brownish in various extents. Postpronotal bristle minute. Acrostichals arranged in 2 irregular rows, hardly separated from dorsocentrals, complete posteriorly; dorsocentrals multiserial, more numerous anteriorly, uniform, complete posteriorly.

Legs entirely yellow. Coxae with unmodified setation; hind trochanter lacking spinules. Fore femur markedly thickened, with row of short yellowish anteroventral and row of minute posteroventral bristles. Fore tibia spindle-like, with unmodified setation. Mid femur slender, with 4 moderately long ventral bristles basally and 1 long, subapical bristle anteriorly. Mid tibia lacking ventral spinules and prominent bristles. Hind femur (viewed laterally) evenly thickened towards middle, with row of moderately long anteroventral bristles on about apical half, row of somewhat shorter anterodorsal bristles and some similar bristles dorsally. Hind tibia unmodified, with unmodified posterior apical comb. Fore and mid tarsi slender, hind tarsomere 1 slightly thickened.

Wing normally developed, covered with uniform microtrichia; distinctly maculate, broadly brownish infuscate along R 2+3 and CuA 1 (except subapical part). Costal vein with short setulae along anterior margin. R 1 (especially in meeting point with costa), R 2+3, R 4+5 and basal part of CuA 1 thickened. R 2+3 rather short, nearly 2.0 times as long as Rs, straight, meeting costa somewhat beyond wing midway. Distance between apices of R 2+3 and R 4+5 nearly 2.5 times longer than distance between apices of R 1 and R 2+3. R 4+5 evenly curved toward costa in apical part. R 4+5 and M 1+2 slightly divergent before wing apex. Haltere with deep black knob and yellow stem.

Abdomen. Tergite 1 pale yellow, remaining tergites brownish; tergites 1–2 unmodified. Segment 8 with 2 long and several short setae. Sternites brownish yellow, with scattered minute brownish setulae, sternites 2–5 divided along midline. Tergites 2–6 with darker lateral patches covered with microtrichia.

Terminalia brown ( Figs. 45–47 ). Right epandrial lamella large, spoon-shaped, dorsally set with a few long setae ( Fig. 45 ). Right cercus narrow with fine hairs. Left cercus larger, with a large ventral projection ( Fig. 46 ); left cercus set with about 6 strong yellow bristles. Apex recurved, pointed ( Fig. 47 ). Left surstylus round with a short seta on dorsal margin ( Fig. 46 ), no other bristling.

Female: Unknown.

Remarks. Stilpon ubinensis , new species resembles very much S. weilingae Grootaert & Shamshev, 2012 . In the key to Stilpon in the Tachydromiinae of Singapore ( Grootaert & Shamshev, 2012) it leads to couplet 8 and to S. weilingae . Most external characters are identical but the male terminalia though similar are distinctly different. In S. ubinensis , new species, the right epandrial lamella is apically rounded and the left cercus is more pointed with a recurved tip and a large inner extension. In S. weilingae the right epandrial lamella is bifid and the left cercus has a different shape (figs. 232–235 in Grootaert & Shamshev, 2012).

Figures

Figs. 45–47. Stilpon ubinensis, new species, male: 45, right epandrial lamella, lateral view; 46, epandrium with cerci, dorsal view; 47, left cercus and surstylus, lateral view. Scale bar = 0.1 mm.