Robertsmyia aureola, Li, 2025

1. Robertsmyia aureola sp. nov.

http://zoobank.org/ urn:lsid:zoobank.org:act:5A933132-7ABF-483C-A80D-03486B2B28F1

( Figs 1–8 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 )

Type specimens. Holotype ♂, Australia, SA, Cadell , MacKintosh Rd., 34°03′50″S 139°44′36″E, 29.iv.2024, MA Newton ( ANIC No. 29-020518) GoogleMaps . Paratypes ♀ (5), Same data as holotype ( ANIC No. 29-020519–29-020523). Australia, SA GoogleMaps , ♂ (1), Pooginook , Goyder hwy., 34°07′16″S 140°03′33″E, 8.v.2024. MA Newton. ( ANIC No. 29- 020524) GoogleMaps .

Diagnosis. Small-sized species, wing length 3.3–6.5 mm. Pedicel moderately elongate, 1.7× longer than wide, without dorsal apical spine. Wing membrane almost uniformly subhyaline, only infuscation along the anterior costal margin. Cell dm greater than 3.5× longer than wide.

Description. Male. Body length 3.8–5.9 mm, wing length 3.3–5.7 mm.

Head. Head ~1.6× wider than long; clothed with dense mid-grey pruinescence, long white and gold hairs, the latter more concentrated dorsally with some adpressed gold scales. Eyes broadly connected by 2.0× length of ocellar tubercle ( Fig. 2 c View FIGURE 2 ). Lower frons small and triangular with pale greyish yellow pruinescence, devoid of hairs; mid frons absent; upper frons bordering ocellar triangle ( Fig. 2 b View FIGURE 2 ). Ocellar tubercle slightly raised, its posterior edge just behind that of the eye margin; black with dark grey pruinescence and numerous blackish setae, variously directed. Face conically produced, 0.8× the length of the scape ( Fig. 1 View FIGURE 1 ); pale greyish-yellow pruinescence; moderately dense, long, whitish-gold hairs; gena vestiture the same and continuous with the face. Occiput with long, gold, reflective hairs and short, gold, reflective, adpressed scales. Posterior eye margin slightly sinuate. Antennae with dense grey pruinescence on all segments ( Figs 2 a, b View FIGURE 2 ). Scape and pedicel both with anteriorly directed, long black hairs; flagellum bare. Scape short, 2.7× longer than wide, slightly wider near apex, 0.3× length of entire antenna. Pedicel 1.7× longer than wide, widest distally, 0.2× length of entire antenna. Flagellum the longest segment, one-segmented, 5.2× longer than wide, widest 0.4× of its length from base, with apical ventral projection and distinctive dorsal spine-like style ( Fig. 6 b View FIGURE 6 ), 0.4× length of pedicel; pinned specimens show the flagellum to be curved with some lateral compression. Palp one-segmented, slender and elongate, blackish grey, concolourous with antennae ( Fig. 2 d View FIGURE 2 ). Mouthparts long (extending well beyond oral cavity), robust, 2.0× head length, 2.5× antennae length ( Fig. 1 View FIGURE 1 ); labellae large and fleshy with five robust pseudotracheae ( Fig. 6 a View FIGURE 6 ).

Thorax. Integumental colour of scutum dark bluish black with dull shine and sparse pale brownish grey pruinescence; anterior third with moderately dense long gold hairs and admixed short reflective gold scales. Hairs and scales most prominent peripherally, integument mostly glabrous dorsally. Scutellum integument concolourous with scutum, short curved adpressed golden scales along lateral and posterior margin, mostly glabrous dorsally. Pleura densely ashy pruinose, integument blackish, mostly with sparse long whitish hairs, except anepimeron, meron, laterotergite and mediotergite bare. Leg I coxae mostly cinereous pruinose; leg II coxae distally yellow, basally cinereous pruinose, both with sparse long whitish hairs; leg III coxae integument yellow with sparse long whitish hairs.

Legs. Legs mostly yellow, hind femur and tibia darkening distally, tarsi mostly yellow, darkening distally to brown-black, trochanters with ventral black mark. Leg II, III tibiae distinctly spinose, leg I minimally. Leg I, II femora with fine, moderately dense white hairs. Legs with whitish yellow scales, most distinct on femora. Leg bristles mostly short and black, some pale bristles present, especially leg I. Fore tibia 1.6× longer than fore basitarsus, mid tibia 2.3× longer than mid basitarsus, hind tibia 2.0× longer than basitarsus.

Wings. Wing membrane uniformly subhyaline with iridescence except for cell sc and wing base with thin brownish yellow infuscation ( Fig. 7 c View FIGURE 7 ). Cell r 5 open; cell br much longer than cell bm; crossvein r-m arising 0.7 from the base of cell dm; crossvein m-m long, nearly as long as crossvein r-m; cell cup open ( Fig. 7 c View FIGURE 7 ). Alula vestigial, small and narrow. Haltere stem yellowish, darkening brown distally into brown area within yellowish knob.

Abdomen. Long and narrow, only tapering apically. Integumental colour of tergites black; tergites I–IV with lateral border distinctly yellowish orange, diminished or absent on tergites V–VIII. Tergite I with moderately dense long gold hairs and some gold scales, similar to anterior scutum. Tergites II–VIII with sparse long fine pale hairs and sparse adpressed gold scales. Sternites with yellowish brown pruinescence and moderately dense whitish-yellow hairs, cream colour distinctly contrasting with tergites. Genitalia. Epandrium and gonocoxites nearly rectangular, sides slightly concave in distal half; length ~1.2× as long as wide ( Figs 5 a, c View FIGURE 5 ). Hypandrium membranous. Ejaculatory apodeme strong; gonocoxal apodeme short and weak with apex pointed; anterior arm of phallic sheath absent; inner and outer apex of gonocoxite rounded; phallus extends just beyond apex of gonocoxite; gonocoxal fusion seam medium; gonostylus pointed dorsolaterally ( Figs 5 a, b, d View FIGURE 5 ).

Female. Body length 3.3–5.5 mm, wing length 4.1–6.5 mm. Female habitus very similar to male ( Figs 3 a, c View FIGURE 3 ) except frons complete with eyes well separated, ~2× width of ocellar triangle mid frons ( Figs 3 b, d View FIGURE 3 ). Tergite 8 with thick, long, fine hairs ( Figs 4 a, b View FIGURE 4 );> 30 acanthophorite spines present in a dense row ( Figs 4 c, d View FIGURE 4 ). Furca sclerites slender, largely parallel, slightly concave, unjointed ( Fig. 4 f View FIGURE 4 ). Spermathecal bulb large, sclerotized and spherical, with small invaginated apical cone ( Fig. 4 e View FIGURE 4 inset). Distal spermathecal duct of normal length; sperm pump short, collars absent ( Fig. 4 e View FIGURE 4 ).

Remarks. Robertsmyia aureola sp. nov. can be readily distinguished from its congener, R. pallidoventris by the antennal pedicel being shorter and lacking a dorsal apical spine; wings subhyaline with cell sc and wing base lightly infuscated brownish. The invaginated cone (in R. aureola sp. nov.) and apical small conical point (in R. pallidoventris ) on the sperm bulb might be the same character. It depends on the pressure differences between the inside and the outside of the sperm bulb during dissection. Vesture variations on the dorsal surface of the scutum are observed in different specimens. These variations most likely indicate the age of the specimen as hairs and scales on the dorsal surface are easier to drop off. Some specimens (often males) of R. aureola sp. nov. display an unusual-shaped abdomen, which is typically long and narrow, only tapering apically that resembles Eclimini species according to the key in Li & Yeates (2018: pp. 326).

Distribution. Riverland, South Australia ( Fig. 8 View FIGURE 8 ).

Etymology. The specific epithet is derived from the Latin, aureolus, meaning glittering gold, in reference to the reflective gold scales on the dorsum of this species.

Collection details. During April of 2024, manual sweep-netting along a roadside nature strip (MacKintosh Rd) near Cadell, South Australia (34°03′50″S 139°44′36″E) of mallee bushes including Dodonea sp. ( Sapindales : Sapindaceae ), Senna spp. ( Fabales : Fabaceae ), revealed five females and one male specimen of R. aureola sp. nov. Capture frequency was low, with only one or two specimens being collected on any given day within an hour. As autumn was well underway, very few plants were in flower and insect activity was generally quite low. Further netting on warmer days in May 2024 revealed more females with no males. No visual observation of these small flies was ever made before netting. In May 2024, one male specimen was collected in a roadside nature strip of sandy mallee at Pooginook, South Australia (34°07′16″S 140°03′33″E).