Trigonocera ubinensis Grootaert, Velde & de, 2024, new species
Creators: name: Grootaert, Patrick
name: Velde
name: Isabella Van de
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Dolichopodidae
Trigonocera
Trigonocera ubinensis

description: Trigonocera ubinensis, new species
(Figs. 8, 9)
Diagnosis. A medium-sized species (about 3 mm long). Scape bare. Males with postpedicel elongate triangular 2–2.5 times as long as wide, arista 1.5 times longer than postpedicel. A long lower propleural bristle. Tergites 1–3 yellowish white with apical border brown. Hind coxa and metepimeron yellow. Female with postpedicel rounded, a little shorter than high.
Etymology. The new species is named after the type locality Pulau Ubin.
Material examined. Holotype male. Singapore, Pulau Ubin, Puaka Hill (PU14), 17 May 2018, (1°24′23.22″N,103°57′3 0.60″E), secondary forest (ZRCBDP0256851 in LKCNH). GenBank accession code: PP893301.
Paratypes. Singapore, 3 males, Pulau Ubin (PU14), 5 April 2018, secondary forest (Ma9837, RBINS): 1 male, Pulau Ubin, PU14, ZRCBDP0256869 _ Nabilah-Kareen _ MIPD17 _ PU14 _ 17May2018.
Barcode: ZRCBDP 0276611_WanTing_SGDolis025_ PU 14_ 12Apr2018 _imaged; whole mitogenome was done by Darren Yeo. GenBank accession code: PP893303.
Other material examined. 19 specimens PU14 (type locality), 3 specimens PU12; 1 specimen PU13; specimen; 1 specimen PU20; 1 specimen NSM1; 1 specimen KM03. In total, 27 specimens were barcoded. They form a cluster of 0.3%, meaning that there is only 1 base pair difference between the haplotypes.
Male. Length: body 2.8–2.9 mm; wing 2.4–2.5 mm.
Head. Frons wide, wider than base of postpedicel. Face wide, parallel-sides a little narrower than frons. A pair of long retro- and lateroclinate ocellars, followed by pair of short proclinate bristles (⅓ length of the anterior bristles). A pair of short postvertical bristle, no vertical bristle. Upper postocular bristles short, black, and uniserial above, below longer, white, and only near mouth a few additional bristles behind the row of postoculars.
Antennae. With brown postpedicel, black scape, and pedicel (Fig. 9). Scape a little longer than pedicel. Pedicel with a dorsal bristle a little longer than width of pedicel. Tip of pedicel conical going inside the postpedicel, but no thumb-like projection on pedicel reaching over the postpedicel. Postpedicel elongate triangular (0.31 mm / 0.15mm), 2 times as long as wide at base. Ventral base of postpedicel not overlapping the pedicel (Fig. 9A). Arista subapical (Fig. 9A, detail of apex) about 1.5 times as long as postpedicel. Palpus white, with a long black apical bristle and 5 short additional bristles.
Thorax. 8 pairs of short acr in anterior half; 4 long dorsocentrals, almost equally long. 2 strong marginal scutellars with a tiny hair at outside. A long propleural black bristle (Fig. 8).
Legs. Entirely yellow, except for the brown mid coxa and a pale brownish patch on the base of the hind coxa. All bristles black.
Fore legs. Coxa with 3 long black anterior bristles in apical half, a few short bristles in basal half, 2 short apical bristles. Femur with 3 preapical posteroventrals as long as femur is wide; 1 short preapical posterior, 3 fine ventrals near middle nearly half as long as femur is wide. Tibia with 1 short dorsal at middle, 1 ad on basal quarter, 1 short preapical dorsal. A pair of very small claws and minute pulvilli.
Mid legs. Coxa with an exterior black bristle at base a little longer than coxa is high and a shorter exterior near apex; anteriorly set with long bristles. Trochanter with 2 strong ventral bristles, longer than trochanter is long. Femur with a row of short anteroventral bristles, half as long as femur is wide. An anterior preapical bristle as long as femur is wide and 2 preapical anteroventrals. Tibia with a short ad near base and strong ad at basal fifth, a strong dorsal near middle and a shorter anteroventral below; 2 strong ventral bristles in apical crown. A pair of very small claws and minute pulvilli.
Hind legs. Coxa with a long exterior at base, as long as coxa is high and a minute bristle near apex. Trochanter with a long anterodorsal bristle. Femur with about 5 fine anteroventral bristles in apical half, half as long as femur is wide; a strong anterior preapical a little longer than femur is wide. Tibia with 5 short posterodorsal bristles; 2 anterodorsal, 3 short anteroventral bristles. A pair of short claws and minute pulvilli.
Wings. Hyaline with a faint brownish tinge, veins brownish. Veins R 4+5 and M 1+2 running parallel in apical half, M 1+2 with a faint bent before middle. Squama yellowish white with very long black bristles; haltere white. Metepimeron entirely yellow.
Abdomen. Tergites 1–3 yellowish white, but apical border of these 3 tergites with a brown rim. Base of tergite 3 also with a brown rim. Tergite 4 with a yellowish spot at side. All tergites with short dorsal bristles and long apical bristles. Tergite 6 lacking bristles. Sternites 1–5 yellowish white; sternites 2–4 each with at least 4 moderately long bristles; no bristles on sternite 5. Tergite 8 (Fig. 9B) with 4 equally strong macrosetae.
Male terminalia. Fig. 9. Cercus yellow including the rounded basal lobe. Apical appendage of cercus at least 3 times as long as basal rounded part of cercus. Dorsal surstylus tubular with an apical bristle (Fig. 9D). Postgonite with rectangular bent near middle, at base swollen with ventral part rounded (Fig. 9C). Ventral surstylus yellowish brown, with apex a little darkened. Epandrial lobe broad, trapezoid with 2 long subapical bristles and a small bristle on the inside, near middle (Fig. 9D).
Female. Length: body 2.9–3 mm; wing 2.3–2.4 mm.
Postpedicel a little shorter than long, with a rounded apex (not triangular). Postpedicel paler brown than the dark brown scape and pedicel. A pair of very long proclinate vertical bristles present, which is absent in males. Proboscis much stouter than in males with a larger yellowish palpus. Bristling and colouration of legs identical to males. Only mid coxa brown, while hind coxa and metepimeron are yellow. Colouration of tergites (tergite 1–3 yellowish white with posterior border browned and tergite 4 mainly brown with a yellow patch at side; tergite 5 entirely brown) and sternites (sternites 1–4 yellowish white, sternite 5 brown) identical to male.
It is difficult to distinguish the females of these Trigonocera in a sample from Diaphorus females. Females have a short pedicel with a rounded apex, while males have a long triangular postpedicel. The two females reported here are associated with the males thanks to the barcoding.
Comments. We refer to the comments made under the previous species Trigonocera pilifer, new species. Trigonocera ubinensis, new species, could be confused with some Diaphorus species in also having a triangular postpedicel. D. longicornis Olejníček, 2005 described from North Laos is such a species with a long triangular postpedicel 1.5 times as long as high, also with only mid coxa brown, and fore and hind coxa yellow. However, the fore tarsus lacks claws and has pulvilli longer than apical tarsomere and the abdomen lacks yellow patches in the latter species.
National distribution. The new species is not very common in Singapore. It is most abundant in the type locality on Pulau Ubin (PU14), a secondary forest on Puaka Hill. It was also recorded from another secondary forest patch along the road in front of the Endut Senin campsite on Pulau Ubin. Single specimens were found in the back mangroves of Sungei [= River] Puaka (PU13) and on Pulau Ubin (PU20), respectively. Only two specimens were found on Singapore island itself: a single specimen in the swamp forest of Nee Soon and one specimen in the swamp forest of Kranji Marshes. A single male was found in Preah Khan (Siem Reap), Cambodia.
description: Published as part of Grootaert, Patrick, Velde, & Isabella Van de, 2024, New long-legged flies from mangroves on Pulau Ubin (Singapore) (Insecta: Diptera: Dolichopodidae), pp. 303-323 in Raffles Bulletin of Zoology 72 on pages 312-314, DOI: 10.26107/RBZ-2024-0025, http://zenodo.org/record/14683054