Prosoeca torquata Theron, 2020

Theron, Genevieve L., Ellis, Allan G. & Midgley, John M., 2025, A revision of a spring-active clade of Prosoeca Schiner, 1867 (Diptera, Nemestrinidae), keystone pollinators from the Greater Cape Floristic Region in South Africa, with descriptions of three new species, ZooKeys 1257, pp. 249-284 : 249-284

publication ID	https://doi.org/10.3897/zookeys.1257.155954
publication LSID	lsid:zoobank.org:pub:7D8BD25C-6BBF-44AE-8E5F-0B055043E470
DOI	https://doi.org/10.5281/zenodo.17488904
persistent identifier	https://treatment.plazi.org/id/76DBCF73-2749-50AE-A12E-CD89888A8DAF
treatment provided by	ZooKeys by Pensoft
scientific name	Prosoeca torquata Theron, 2020
status

Treatment

Prosoeca torquata Theron, 2020 View in CoL

Figs 1 View Figure 1 , 3 A View Figure 3 , 4 A View Figure 4 , 5 A View Figure 5 , 6 A View Figure 6 , 7 A, B View Figure 7

Prosoeca torquata Theron, 2020: 29. View in CoL

Type material examined.

Holotype: South Africa • ♂ Northern Cape, Steinkopf, Kosiesberg ; -29.12631, 17.55686; 3 Aug 2019; F. Grenier leg.; NMSA -DIP 166602 ; NMSA GoogleMaps . Paratypes: South Africa • 1 ♀ N. Cape, Steinkopf, Kosiesberg ; -29.12631, 17.55686; 3 Aug. 2019; T. van der Niet leg.; NMSA -DIP 166605 ; NMSA GoogleMaps . • 1 ♂ 3 ♀♀ Cape, Steinkopf, Kosiesberg ; -29.12631, 17.55686; 3 Aug. 2019; F. Grenier leg.; NMSA -DIP 166602 –166606; NMSA GoogleMaps . • 3 ♂♂ Northern Cape, Springbok, Naries ; -29.69043, 17.66491; 4 Aug. 2019; F. Grenier leg.; NMSA -DIP 166607 –166609; NMSA GoogleMaps . • 1 ♀ 1 ♂ Steinkopf, Kosiesberg ; -29.12631, 17.55686; 3 Aug. 2019; T. van der Niet leg.; RMCA ENT 13300 View Materials , RMCA -ENT 13301 ; RMCA GoogleMaps .

Other material examined.

South Africa • 1 ♂ Northern Cape: Kamiesberg: Leliefontein ; 19 Oct. 2008; 34 visiting Satyrium erectum ; T. van der Niet leg.; NMSA -DIP 219367 ; NMSA. • 1 ♀ Northern Cape: Nama Khoi: Naries ; 29.701°S, 17.665°E; Spring 2009; T. van der Niet leg.; Satyrium erectum ; NMSA -DIP 219347 ; NMSA. GoogleMaps • 1 ♂ Northern Cape: Steinkopf: Kosiesberg ; 26 Aug 2016; Bruce Anderson leg; NMSA -DIP 221846 ; NMSA • 2 ♂♂ 1 ♀ Northern Cape: Namaqualand: Kamiesberg: 2 km S of Leliefontein ; 17 Sep. 1992; F. W. and S. K. Gess leg.; On pink flowers of Pelargonium cf. incrassatum ; AMGS -ENT 101691 –101693 AMGS. • 2 ♂♂ 2 ♀♀ Northern Cape: Namaqualand: Kamiesberg: 2 km S of Leliefontein ; 12 Sep. 1992; F. W. and S. K. Gess leg.; Flowers: Hesperantha paucifolia ( Iridaceae ); AMGS -ENT 101694 –101697; AMGS. • 1 ♂ Northern Cape: Namaqualand: Kamiesberg: 2 km S of Leliefontein ; 13 Sep. 1992; F. W. and S. K. Gess leg.; On deep pink flowers of Pelargonium sp. ( Geraniaceae ); AMGS -ENT 101698 ; AMGS. • 1 ♂ Northern Cape: Namaqualand: Kamiesberg: 2 km S of Leliefontein ; 17 Sep. 1992; F. W. and S. K. Gess leg.; AMGS -ENT 101700 ; AMGS. • 1 ♂ Northern Cape: Namaqualand: Kamiesberg: 2 km S of Leliefontein ; 12 Sep. 1992; F. W. and S. K. Gess leg.; AMGS -ENT 101699 ; AMGS. • 1 ♂ 1 ♀ Namaqualand: Bowesdorp ; SA Museum staff leg.; Sep. 1941; SAM-DIP A 009011 ; SAMC . NAMIBIA • 1 ♀ Namuskluft 88:! NamiNus constituency (on label as Luderitz); SE 2710 Dd; 20–22 Sep. 1973; H 14602 ; NMNW .

Diagnosis

(adapted from Theron et al. 2020). Medium- to large-sized (length 12–21 mm), dark body, with intricate patterns on the abdomen, dark brown legs, proboscis length 1.10 ± 0.02 × the length of the body (range of un-extended proboscis length 14–24 mm), and patterned smoky brown infuscation on the anterior 1 / 2 of the wing. Prosoeca torquata , P. marinusi Barraclough, 2018 and P. peringueyi Lichtwardt, 1920 can be distinguished from all other species in the clade by their proboscis which is longer than the length of their bodies, in contrast to P. ora sp. nov., P. aquilo sp. nov. and P. parva sp. nov. that have a proboscis shorter than the length of their body. Prosoeca torquata and P. peringueyi both have a distinct dark smoky brown wing anterior, abruptly becoming hyaline on the posterior section (Fig. 5 A, C View Figure 5 ). Prosoeca torquata differs most noticeably from P. peringueyi and P. marinusi , by the presence of a white band of pile on the anterior of the thorax and white pile on the face (Figs 3 A View Figure 3 , 6 A View Figure 6 ), which is largely lacking in the latter two species. Additionally, P. torquata has a darker thorax than P. peringueyi . Prosoeca torquata generally has a proboscis that is only slightly longer than the body, in comparison to P. marinusi and P. peringueyi , which both have a proboscis substantially longer than the body. Prosoeca torquata can be found north of the Knersvlakte to the southern part of Namibia.

Redescription.

Male. Body length: mean 15.7 mm; range 12–21 mm ( n = 42). Intertegular width: mean 6.1 mm; range 4–8 mm ( n = 12). Proboscis length: mean 17.8 mm; range 14–24 mm ( n = 33). Wing length: mean 16.5 mm; range 12–19 mm ( n = 14).

Head. (Figs 4 A View Figure 4 , 6 A View Figure 6 ) Ground colour generally red-brown to dark brown or black. Ocellar tubercle somewhat bulbous and developed, just evident above upper eye margin in profile, with dense silvery pruinescence and long black pile; width between eyes at the anterior ocellus 2.2–2.5 × the length of the anterior ocellus; anterior ocellus separated from posterior ocelli by shallow transverse groove. Frons trapezoid; width anterior to ocellar tubercle 0.6 × the width above antennal insertions; slightly to moderately swollen between antennal insertions and anterior ocellus; swelling recedes strongly towards eye margin; pruinescence relatively dense, silver to brown; pile generally absent. Antenna with scape 1.2–1.5 × length of pedicel; first flagellomere longer than the length of scape + pedicel; style subequal to or longer than scape + pedicel + flagellomere 1; ground colour transitioning to a darker hue, on the proximal side of the first flagellomere, style darker than remainder of antenna; scape, pedicel and flagellomere 1 with irregular silver to brown pruinescence; pedicel with mostly elongate black pile, flagellomere 1 with short black pile basally on the dorsal side. Facial area bulbous in profile, with horizontal groove present; sublaterally irregular yellow-brown; with silver to brown pruinescence, but pruinescence largely absent from medial section of face; pile mostly white, elongate, dense, more dense than on frons. Gena with pile a mixture of black and white to pale yellow, elongate, and dense, forming the beard. Proboscis 0.9–1.3 × the length of the body, black with dorsal part of basal 1 / 3–1 / 2 brown. Palpus with first segment significantly longer and much wider than the second segment; colour generally dark brown to black; pile longer on the first segment.

Thorax (Figs 3 A View Figure 3 , 4 A View Figure 4 ). Scutum dark grey to black; pruinescence mostly brown, with pale grey to silvery pruinescence along the lateral sides of the scutum, joining on scutellum; median and paired sublateral vittae evident but never striking, or indistinct; pile mostly black, sparse, shorter than the pile posterior on the scutellum; pile on postpronotal lobe and anterodorsal region of scutum white, dense forming broad collar; postalar callus with black pile dorsally, ventral side with a tuft of white pile. Scutellum with distinct darker central dot or diamond; anterior margin covered by silver to brown pruinescence; posterior margin with a dark, black border; pile on disc of scutellum black, relatively long, sparse compared to scutum; pile along posterior margin elongate, a mixture of black and pale, white or yellow, dense compared to disc of scutellum; with some pale yellow to golden pile laterally. Pleuron mostly blackish; with silver pruinescence, sparser than on scutum; pile generally a mixture of black and white to yellow, relatively long, of intermediate density; most dense and elongate in two tufts, ventral and anterior to the base of the wing and between postalar callus and posterior spiracle; tuft of pile anterior to wing base directed posteriorly, mostly white to golden with some black pile; tuft of pile on katatergite directed posteriorly, black and golden; katepimeron with pile absent, or sparse elongate white pile. Legs. Coxae yellow brown to dark brown; with pile mostly off-white to golden, elongate, dense. Trochanters mostly blackish, with some yellow-brown colouring; pile short, very sparse. Femora yellow-brown, with dark marking on dorsal side of the distal end present; pile mostly black, mostly short, dense, but with elongate pile dorsally on proximal 1 / 3–1 / 2; ventral pile typically longer, sparse; hind femur with short pile more evenly distributed than on fore and mid femora. Tibiae yellow-brown to dark brown; with dense, short, pale pile and sparse, elongate, darker pile (sometimes only short pile present), most dense on hind tibia. Tarsi red-brown to dark brown, hind tarsi tend to be darker. Wings (Fig. 5 A View Figure 5 ). Shape relatively slender; broadest just basal to termination of CuP on posterior margin; alula broad; costal margin close to straight, without distinct anteriorly curved flexure; Sc termination on C aligned with termination of M 4 on posterior margin of wing; R 1 terminated closer to R 2 + 3 than to Sc; termination of Sc and R 1 well separated; short appendix just beyond fork on R 4 + 5 sometimes present; cross vein between M 1 and M 2 absent; cross vein between R 4 and R 2 + 3 absent; R 1 relatively straight; R 4 and R 5 deeply bowing upward; M 1 and M 2 gently bowing upward; cell cua open at margin; CuA and CuP well separated. Dark marking on R 1 positioned just basal to humeral cross vein; membrane with smoky brown infuscation; appearing darker on anterior 1 / 2–1 / 3 of wing; posterior region of wing mostly hyaline; isolated darker patches distinct in hyaline region; the distinction between brown infuscation and hyaline membrane sharply delineated. Tuft of pile on base of wing white. Haltere with pale brown to yellow stalk; bulb dark brown.

Abdomen (Fig. 3 A View Figure 3 ). Colour of abdomen generally red-brown; T 2 with posterior margin stout and relatively broad; abdomen tapering abruptly after T 3. Tergites with brown or silvery pruinescence; membrane between T 1 and T 2 with silvery to brown pruinescence; medial brown pruinescent vitta distinct, extending from the posterior margin of T 1 to terminalia, usually not covering the full length of each tergite; paired sublateral markings of indistinct shape, on T 2 – T 4. Pile on tergites mostly black, both long and short, of intermediate density; along anterior margins of T 2 white to pale yellow, elongate, sparse; posterolateral pile on T 2 – T 4 black, elongate, dense; T 5 with pile along lateral margins more evenly distributed than that of T 2 – T 4. Sternites typically paler than tergites; pale reddish brown; pruinescence silvery, relatively sparse. Sternites with pile a mixture of black and white, mostly short, sparse; pile on S 1 – S 3 intermixed, long, black or white; pile on membrane adjacent to lateral margins of S 2 – S 4 typically with profuse, decumbent, elongate, white pile.

Genitalia (Fig. 7 A, B View Figure 7 ). Hypandrium triangular in shape; relatively narrow, tapering gradually towards the apex; laterally straight sided; 1.8 × longer than basal width; with apical 1 / 5 projecting past the top of the gonocoxites. Hypandrium vestiture short, sparse, on apical 1 / 3. Gonocoxite apical 1 / 2 parallel sided; gonocoxites widest in basal 1 / 2, narrowing apically; rounded apically. Gonocoxite vestiture on the lateral 1 / 2 of apical 1 / 2 long, laterally projecting. Gonostylus narrowed medially; with globular apical section. Phallus near parallel sided; narrowing apically.

Female. Same as male, except for genitalia dimorphism and the following characters: Head. Ocellar tubercle width between eyes at the anterior ocellus 3–3.5 × the length of the anterior ocellus. Frons width anterior to ocellar tubercle 0.8 × the width above antennal insertions.

Geographical distribution.

Prosoeca torquata occurs between Namuskluft in Namibia (single NMNW specimen) in the north and the Knersvlakte region in the Northern Cape Province at Uilklip in the south and is generally abundant when host plants are flowering (Fig. 1 View Figure 1 ).

Biology.

The P. peringueyi complex, including P. torquata , is known to visit many plant species ( Manning and Goldblatt 1996, 2000; Pauw et al. 2020) in both Fynbos and Succulent Karoo biomes. It is, however, not precisely known whether P. peringueyi and P. torquata are pollinators of the same suite of plants, or if they partition floral resources. Prosoeca torquata is known with some certainty, from specimen labels, to visit Lapeirousia silenoides , Pelargonium echinatum , Pelargonium crithmifolium , Satyrium erectum , Pelargonium incrassatum , and Hesperantha pauciflora . Published data that do not refer to vouchered specimens are of unclear value, as they may refer to P. torquata or P. peringueyi .