Thinophilus chaetulosus, Grootaert, 2018

Grootaert, Patrick, 2018, Revision of the genus Thinophilus Wahlberg (Diptera: Dolichopodidae) from Singapore and adjacent regions: A long term study with a prudent reconciliation of a genetic to a classic morphological approach, Raffles Bulletin of Zoology 66, pp. 413-473 : 421-425

Thinophilus chaetulosus sp. nov.

(Figs. 8, 9)

Material examined. Holotype: SINGAPORE, Sungei Buloh , 27 November 2003 (sample 23090, leg. P. Grootaert) . Paratypes: THAILAND: 1 male, Songkhla, 14 October 1999 (leg. P. Grootaert) ; 1 male, Laempho, Hat Yai (Songkhla prov.), 27 June 2015 (leg. A. Samoh; in coll. RBINS) NGS barcode available as chaetulosus_022_ ABDO05 ). The latter clusters at 9.5% with T. clavatus Zhu et al., 2006 from southern Thailand .

Male. (Fig. 8) Body length 5.5 mm, wing length 4.7 mm.

Head. Frons and face with dark metallic green ground colour with blue reflections. Face at its narrowest part in middle as wide as depth of third antennal segment. Clypeus about 1/5 length of epistoma, a little protruding. Palpus yellow, bearing few black bristly hairs. Rostrum dark brown, with white hairs. Postcranium shining dark metallic green. 2 long diverging ocellars; 2 short, converging verticals, pointing forward (a third of length of ocellars); 2 minute postocellars; 2 short postverticals, twice as long as postoculars; postoculars above black, uniseriate; in lower half, white, thickened and also uniseriate; a few long white hairs around mouth.

Antenna. Basal segments ventrally yellow, dorsally brown. Third segment with dorsal and apical half brown (Fig. 8); a little longer than high with an obtuse tip. Arista dorsal, 2–2.5 times as long as antenna, black, very shortly pubescent; basal aristal segment very short.

Thorax and scutellum shining dark metallic green with two ill-limited darker stripes running down the rows of dc, with in between them a brightly shining green area. A long black stripe running from upper part of notopleura to above the insertion of the wings and the area below the alar calli black. No acr; 7–9 dc i.e., 5–7 very short (as long as first antennal segment), followed by a dc that is twice as long and the row ends in a long prescutellar (longer than three antennal segments together). A pair of long marginals with a hair at each outer side. A short humeral with a longer posthumeral; one strong notopleural, a very long pre-alar; a strong alar. Propleura with at least 8 long white hairs above and a group of 8 short white hairs below.

Legs. Fore coxa yellow, but a black streak exteriorly at base; mid and hind coxae black with yellow tips. Legs yellow, but tip of all tibiae narrowly brown; apical tarsomere of all legs entirely black.

Fig. 8. Thinophilus chaetulosus sp. nov., male habitus.

Fore leg. (Fig. 9B) Coxa anteriorly with a double row of long fine black bristles (longer than coxa is wide) with a curved tip; apically with a row of shorter bristles. Femur ventrally near base with a double row of black bristles, half as long as femur is deep; near middle there are additionally a number of pale hairs; in third apical quarter a number of posteroventral bristles and two distinct pre-apical pv. Fore tibia with a short ad and pd in apical third, a short ad in apical third. Anteroventrally with a row of short spinules; ventrally with a double row of diverging bristles (bristles near middle longer than tibia is deep). First tarsomere with spinules ventrally. Following tarsomeres with a pair of apical hairs.

Mid leg. Mid coxa with a long, fine black exterior. Mid femur thickened in basal half, apical half more slender; with a short anterior bristle on apical quarter and a row of erect posterior bristles (half as long as femur is deep) in apical third. Ventrally with a double row of short ventral bristles (less than half as long as femur is wide), with some additional bristles in basal quarter. Mid tibia with an ad in basal fifth, 2 pd and 1 pv, 4 apicals.

Hind leg. Hind coxa with a fine black exterior (shorter than on mid coxa). Hind femur thickened in basal half; apical half more slender; with 4 erect anterodorsal bristles and a row of short ventral bristles. Hind tibia with 3 ad and 3 pd, two short ventrals, and 4 apicals.

Fig. 9. Thinophilus chaetulosus sp. nov. male. A, Antenna; B, Fore leg posteriorly; C, Wing; D, Male terminalia ventrally; E, Male terminalia lateral. Scale = 0.1 mm.

Fig. 10. Thinophilus clavatus Zhu, Yang & Masunaga, 2006 , male habitus. Wing feebly brownish tinged, without darker shades. Veins yellowish brown near base, black in apical two thirds. Apical part of M 1+2 practically straight, running parallel with R 4+5. Tp straight, nearly as long as apical part of M 3+4. Anal vein indicated by a brown streak on basal third only. Haltere white. Squama white, with white cilia.

Abdomen shining dark metallic green. Hairs and hind-marginal bristles on tergites short, black. Sternites without bristles, only a very short white pubescence. Male terminalia (Fig. 9D, E). Cercus long, brown with long white apical hairs. Cerci dorsally fused in basal half. Surstylus with 2 black subapical spines (Fig. 9E).

Female. Unknown.

Remarks. Thinophilus chaetulosus sp. nov. is very similar to T. clavatus Zhu, Yang & Masunaga, 2006 . In the new species the apical tarsomere of all the legs are entirely black while the other tarsomeres are yellow. In T. clavatus all tarsomeres of the fore leg are narrowly but distinctly darkened and only the apical half of the apical tarsomere is black. The posteroventral bristles on the apical half of the fore femur are longer than the femur is wide in T. clavatus (Fig. 10) but not so long and not so dense in the new species. In T. clavatus tarsomere 1 of the fore leg is a thickened at the base and the ventral spinules are strong (Fig. 10). A row of long posteroventral bristles is present on fore tibia and tarsomere 1. In T. chaetulosus sp. nov. the base of tarsomere 1 is not thickened and the ventral spinules are weaker; the posteroventral bristles on the fore tibia and tarsomere 1 are shorter. The male terminalia are similar in both species.

Remarkable and unusual is that the specimen from Brunei (Borneo) has exactly the same NGS barcode as the specimen from Songkhla (southern Thailand).