Pseudogaurax sexnotatus Ismay & Ang, 2019

Ismay, Barbara & Ang, Yuchen, 2019, First records of Pseudogaurax Malloch 1915 (Diptera: Chloropidae) from Singapore, with the description of two new species discovered with NGS barcodes, Raffles Bulletin of Zoology 67, pp. 412-420 : 413-415

Pseudogaurax sexnotatus Ismay & Ang , new species

( Fig. 1 )

Type material. Holotype (here designated), female: SINGAPORE, Nee Soon Swamp Forest , from Malaise Trap NS1 [1°23′00.3″N 103°48′46.5″E] (Collection event: 29246, 17-25.xi.2011). Specimen code ZRC _ BDP0025357 , deposited in the LKCNHM ( ZRC). Cytochrome oxidase I ( COI) partial-cds for this specimen deposited in GenBank under reference MK 541947 .

Diagnosis. In female, almost entirely yellow species with six black thoracic markings and entirely yellow legs.

Description. Length. Body 2.31 mm, wing 2.25 mm.

Head. ( Fig. 1 A–C). Broader than deep (ocelli to proboscis) and longer (occiput to antennal sockets) than deep (1.16: 0.72: 0.78 mm), entirely yellow except for black pubescent arista with hairs twice as long as base of arista, blackened dorsal margin of postpedicel, blackened outer lateral margin of pedicel and black ocellar tubercle (the raised part within the ocellar triangle, delimiting the ocelli). Head and thoracic setae yellow. Ocellar setae short, reclinate and cruciate, equal to length of ocellar tubercle. About eight long, thin, pale, reclinate orbital setae developed, increasing in size posteriorly, the most posterior equal in length to width of palpus. Outer vertical seta strongly developed, as long as postpedicel is deep, lateroclinate and slightly reclinate; inner vertical seta as long as postocellars, incurved and proclinate, circa half-length of outer vertical seta, postocellar setae strongly developed, long, cruciate and reclinate, equal to outer vertical seta. Frons slightly broader than long (0.47: 0.34 mm), width measured at level of anterior ocellus, lateral margins of frons parallel, anterior margin in middle slightly convex, yellow, dusted with two rows of long, pale setulae along outer margin of ocellar triangle. Ocellar triangle bare, large, extending into a point to about one palpus width away from anterior margin, posteriorly to almost width of frons, distance between posterior corner and eye margin as wide as 1.5 times the width of an ocellus, lateral margins slightly concave, shiny, pale orange. Eye oval, long axis vertical with short, dense pubescence. Face pale yellow, dusted, slightly broader than deep, strongly concave; faint carina present, not visible below antennae; antennae pale yellow, postpedicel reniform, deeper than long, as long as palpus, black around insertion of arista; arista basal, black, with strong short pubescence (twice as long as basal diameter of arista), 1.2 times as long as postpedicel; gena very narrow, as deep as width of base of arista, pale yellow slightly shiny, one row of pale setulae on genal margin, as long as depth of antenna, vibrissal angle obtuse; occiput yellow, very narrow in lateral view, as wide as twice the width of the base of the arista; proboscis pale yellow, short, weakly sclerotised; palpus pale yellow, slightly longer than antenna, slightly curved dorsally, with several long, pale setulae; mouth edge slightly protruding; clypeus pale yellow.

Thorax. ( Fig. 1A, B ). Scutum slightly broader than long (0.75: 0.66 mm), yellow, with three stripes, the central black longitudinal stripe starting the width of the postpedicel posteriorly from the anterior margin as thin as the tip of the arista, ending at the posterior margin being half as wide as the postpedicel, the outer lateral stripes starting immediately posteriorly of suture widening into a broad triangle shape, ending just before posterior post alar bristle; a faint darker mark present on the dorsal notopleuron, separated from the transverse suture by a yellow band; scutum entirely shiny with dense, medium long, pale setulae; one posterior dorsocentral seta developed, as long as second apical anterior tarsus, no acrostichal setae developed; postpronotal lobe yellow with one long seta at lateral posterior margin, equal to ocellar setae; the dark brown mark surrounding the pale anterior spiracle as large as half the postpedicel; notopleuron yellow with 1 plus 2 long yellow setae, as long as the inner vertical seta, but the upper posterior seta slightly shorter; posterior post-alar seta yellow and as long as outer vertical seta. Pleura entirely shiny, and mostly bare, all yellow except for ventral half of anepisternum black, with faint metallic reflections, except for a fine yellow line at the ventral and posterior margin, front margin of katatergite with a black line twice as thick as the base of the arista at lower margin widening to smudgy dark grey mark in upper third, at upper margin 1.5 times as wide as arista including pubescence, anatergite with longitudinal dark grey smudgy mark along apical third of outer margin, postnotum light orange, shiny, ventral margin of katepisternum with several very long setulae, haltere very pale, almost white. Scutellum yellow with large black central mark, covering c. 80% of flattened disc of scutellum, leaving lateral and posterior margin yellow, shiny, about as long as wide (0.31: 0.34 mm), shield-shaped, disc and lateral margins with even but small black setulae; apical scutellar setae broken off, not approximated, originating from small tubercles, four pairs of short yellow lateral scutellar setae originating from small tubercles. Haltere pale yellow.

Wing. ( Fig. 1B ). Translucent with brown veins, covered in sparse brown microtrichia and long setulae along costal margin; costal ratios measured from base of basicosta to point where R 1 touches Costa, then along costal margin of r 2+3, then along costal margin of r 4+5: 0.91: 0.69: 0.41: 0.25 mm; cell r 1 broader than cell r 2+3, veins R 4+5 and M 1 almost parallel up to costal wing margin, where they diverge very slightly, distinct kink in M 4, costal break basal to where R 1 touches Costa, basicosta white.

Legs. ( Fig. 1B ). All legs yellow, shiny, covered in yellow setulae that are longer than twice the width of the base of the arista; coxa pale yellow, basal third of femur pale yellow, mid and posterior femora and tibiae slightly darker yellow in apical two thirds; posterior femora and tibiae 1.5 times as thick as mid femora and tibiae; apical four left middle tarsal segments missing; yellow apical anteroventral straight spur on mid tibia as long as tibia is thick, femoral or tibial organ absent; apical tarsal segment scarcely wider than basal segment.

Abdomen. Ventrally white, anterior margin of tergite 1+2 white, middle third of posterior margin white, lateral thirds dark brown thus forming a trapezoidal white mark in middle; middle fifth of tergite 3 white at anterior margin forming a white triangle with a blunt end to posterior margin, laterally dark brown; tergites 4 and 5 dark brown, each with a small white spot in middle of anterior margin; all tergites with relatively long pale setulae; lateral thirds of tergite 4 dark brown.

Female terminalia. ( Fig. 1C ). Not extended, but tergite 6 dorsally black, laterally white; tergite and sternite 8 white, cercus long, as long as apical two anterior tarsi, black, with two very long, fine pale setulae as long as outer vertical.

Barcode. Cytochrome oxidase I (COI) partial-cds (313 b.p.; GenBank accession code MK541947 ) as follows:

---tttatcttcaattattgctcatggaggagcttcagttgatttagcaattttttcact tcatttagctggagtatcttcaattttaggagcagtaaattttattactacagtaattaa tatacgttcaacaggaattacatttgatcgaatacctttatttgtatgatcagtagtaat tactgctttacttcttcttttatcattacctgtattagctggagctattactatattatt aactgatcgaaatttaaatacttcattttttgatccagctggaggaggagatccaatttt ataccaacatttattt

Etymology. The species name sexnotatus (six and marked) is derived from Latin, referring to the six distinct black marks on the thorax.

Remarks. This new species runs to couplets 6 in the keys by Ismay (1987) and by Cherian (2013), but this species does not agree with either of the two parts of these couplets. This species differs from both sides of couplet 6 in Ismay (1987) in that the scutellum is yellow with a wide central black stripe, whereas in couplet 6 the scutellum is differently coloured. It disagrees with Cherian (2013) couplet 6 in that it’s ocellar triangle does not reach the anterior margin of the frons (as in P. sabroskyi ), but the scutellum is longer than wide, while it ought to be wider than long in the second part of the couplet. It is therefore regarded as a new species.

Figures

Fig. 1. Habitus of holotype of Pseudogaurax sexnotatus, new species (female, specimen ZRC_BDP0025357). A, dorsal habitus showing dorsal scutum and scutellum, as well as head capsule in oblique view, note the six distinct spots on thorax; B, lateral habitus showing thoracic pleura, head, legs and wing, as well as terminalia behind wing; C, dorsal view of head.