Afroxanthandrus congensis ( Curran, 1938 ), 2024

Midgley, John M., Goergen, Georg & Jordaens, Kurt, 2024, A revision of the Afrotropical hover fly genus Afroxanthandrus Kassebeer, 2000 (Diptera, Syrphidae), with the description of two new species and one new synonymy, European Journal of Taxonomy 968, pp. 60-85 : 68-74

Afroxanthandrus congensis ( Curran, 1938) stat. rev.

Figs 1 , 3, 5 , 8 , 10 , 12 , 14, 16 , 20–21 , 24

Xanthandrus congensis Curran, 1938: 18 . Type-locality: Congo. Lukolela (HT ♀, AMNH).

Xanthandrus magnificus Goeldlin de Tiefenau & Thompson, 2019: 160 syn. nov.

Xanthandrus congensis – Smith & Vockeroth 1980: 494 (catalog citation). — Dirickx 1998: 139 (catalog citation). — Goeldlin de Tiefenau & Thompson 2019: 162.

Afroxanthandrus congoensis [lapsus] – Kassebeer 2000b: 154, figs (antenna, head, ♂ genitalia) (new combination, description). — Whittington 2003: 586 (citation).

Diagnosis

Differs from A. comorosensis sp. nov. and A. conopeum sp. nov. in the curved posterior margin to the yellow fascia on tergite 2 (margin straight in A. comorosensis and A. conopeum ) and from A. longipilus in the large, rounded fascia on tergite 3 (narrow in A. longipilus ). Genitalia large, superior lobes about twice as long as surstyli (shorter than surstyli in A. comorosensis and A. conopeum ).

Type material examined

Holotype of Xanthandrus congensis (photographs only)

DEMOCRATIC REPUBLIC OF THE CONGO • ♀; Équateur Province, Lukolela; 16 Dec. 1930; J.P. Chapin leg.; AMNH .

Lectotype of Xanthandrus magnificus (hereby designated)

CAPE VERDE ISLANDS • ♂; Praia Region, São Tomé ; 16 Mar. 1977; J. Denon leg.; MZLS .

Paralectotypes of Xanthandrus magnificus (hereby designated)

CAPE VERDE ISLANDS • 1 ♀; same data as for holotype; MZLS • 2 ♂♂; same data as for holotype; USNM, USNMENT01842018 , USNMENT01842995 • 2 ♀♀; same data as for holotype; USNM, USNMENT01842019 , USNMENT01842996 .

Other material examined

CENTRAL AFRICAN REPUBLIC – Prefecture Sangha-Mbaéré • 1 ♀; Parc National de Dzanga-Ndoki , Mabéa Bai 21.4 km 53° NE of Bayanga; 3°02.01′ N, 16°24.57′ E; elev. 510 m; 2 – 3 May 2001; S. van Noort leg.; Malaise trap, CAR01-M19, lowland rainforest, marsh clearing; SAMC, SAM-DIP-A016873 • 1 ♀; Réserve Spéciale de Forêt Dense de Dzanga-Ndoki , 12.7 km 326° NW of Bayanga; 3°00.27′ N, 16°11.55′ E; elev. 420 m; 12–13 May 2001; S. van Noort leg.; Malaise trap, CAR01-M102, lowland rainforest; SAMC, SAM-DIP-A016988 • 1 ♂; same data as for preceding; 11–12 May 2001; Malaise trap, CAR01-M94; SAMC, SAM-DIP-A016919 .

DEMOCRATIC REPUBLIC OF THE CONGO – Tshopo Province • 1 ♀; Gazi ; 2 Aug. 1940; J. Vrydagts leg.; RMCA, RMCA ENT 000056902 . – Maniema Province • 1 ♀; Kasongo area ; Dec. 1959; P.L.G. Benoit leg.; RMCA, RMCA ENT 000056903 .

ETHIOPIA • 1 ♂; Oromia Region, Jimma, Girmo ; 07°52′49″ N, 36°51′51″ E; elev. 1961 m; 19 Feb. 2016; L. Geeraert leg.; random sweepnetting, semi-forest coffee management system; Plot 2; Dani; 12:00; AHE_251; DNA 702C02 K. Jordaens RMCA 2016; AB49487198; GenBank: OM952147 ; RMCA, RMCA ENT 000028396 .

REPUBLIC OF THE CONGO – Sangha Department • 2 ♂♂; Nouabalé-Ndoki National Park , Mbeli camp ; 2°14′23.8″ N, 16°23′52.1″ E; elev. 372 m; 14–20 Feb. 2023; N.M. Bakala, V. Derozier, A. Kirk-Spriggs and G. László leg.; carrion bait; ANHRT 2023.3; ANHRT, ANHRTUK 00282353 , ANHRTUK 00282359 • 1 ♂; same data as for preceding; RMCA DNA 1587B08, GenBank: PP828576 ; ANHRT, ANHRTUK 00282358 • 1 ♀; same data as for preceding; RMCA DNA 1587C01, GenBank: PP828577 ; ANHRT, ANHRTUK 00282352 • 3 ♀♀; same data as for preceding; ANHRT, ANHRTUK 00282354 , ANHRTUK 00282355 , ANHRTUK 00282357 • 1 ♂; same data as for preceding; banana bait; ANHRT 2023.3; ANHRT, ANHRTUK 00282232 • 2 ♀♀; same data as for preceding; 15–19 Feb. 2023; Malaise trap; ANHRT 2023.3; ANHRT, ANHRTUK 0028282813 , ANHRTUK 00282814 • 1 ♀; Nouabalé-Ndoki National Park , Mondika camp ; 2°21′50.63″ N, 16°16′25.83″ E; elev. 365 m; 7–14 Feb. 2023; N.M. Bakala, V. Derozier, A. Kirk-Spriggs and G. László leg.; carrion bait; ANHRT 2023.3; ANHRT, ANHRTUK 00282680 • 1 ♂; Nouabalé-Ndoki National Park , Bomassa camp ; 2°12′36.9″ N, 16°11′30.2″ E; elev. 365 m; 6–14 May. 2023; V. Derozier, A. Kirk-Spriggs, G. László and S. Mvouende leg.; carrion bait; ANHRT 2023.6; ANHRT, ANHRTUK 00311540 .

Description

MEASUREMENTS. Body: 8.3–11.8 mm; wing: 6.9–8.5 mm.

Male

HEAD ( Fig. 3 ). Black, with small to medium facial tubercle and a medium sized antennal prominence. Face straight in profile; widest just below the antennae, approximately 44% of the maximum head width, slightly narrowed ventrally, narrowest in line with dorsal oral margin, approximately 38% of maximum head width; covered with dense, yellowish-white pollinosity, completely obscuring the black ground colour, thinner pollinosity on the oral margin and gena, facial tubercle bare; with short, light yellowish pilosity, medial region bare from oral margin to antennal base. Frons with dense yellowish-white pollinosity, reaching from the eye contiguity to the base of the antennal prominence. The antennal prominence and lunule are bare, the lunule orange in ground colour while the prominence dark brown to black. Frons with short light yellow pilosity, sparse on lunule and antennal tubercle. Vertical triangle with very short, dark brown pilosity anteriorly (shorter than the width of the anterior ocellus) which get gradually longer and paler posteriorly, golden at posterior margin; vertex elongated, very narrow, angle at eye contiguity approximately 25°; ocellar triangle acutely angled, clearly raised, anterior ocellus round, posterior ocelli oval, about 1.4 times as long as wide. Occiput with pale brown to dark yellow pilosity dorsally, yellow laterally, thin dorsally but broad and scale like laterally; with pale yellow white pollinosity. Eyes bare, kidney-shaped in lateral view. Frontal ommatidia slightly enlarged only in a small area above the antennae. Antennae orange-brown; elongate, as long as or slightly longer than the maximum width of the face, narrow, parallel sided in lateral view, on dorsal side pedicel about 1.5 times the length of the scape, postpedicel twice the length of the pedicel. Scape and pedicel with short thick dark brown pilosity, postpedicel with sparse pollinosity, bare. Arista bare, inserted basally, about 1.3 times the length of the postpedicel.

THORAX ( Fig. 8 ). Scutum evenly rounded, except for a small raised oval bump on each side, anterior to the suture, black; postpronotum and postalar callus brownish, postalar callus with fine light and dark brown pilosity. Pilosity short dorsomedially, longer laterally, light brown, each pilus on a small, rounded, raised, non-pollinose base. Scutal pollinosity densest between the suture and postpronotum, along the suture and in a wide strip in front of the scutellum, light yellow-brown. Less dense on the remainder of the scutum, with some indistinct longitudinal stripes anterior to the suture. Scutellum very broad and large, ~60% the width and ~45% the length of the scutum; dark brown to black; pilosity denser than on the scutum, the density of the raised bases making the surface rough and the margin appears serrated; base narrowly bare, smooth; with a long, multi-rowed, light subscutellar fringe. Pleura dark brown to black; evenly rounded except for a moderate bulge on the posterolateral anepisternum; yellow to white pollinose, most dense on the posterior anepisternum and katepisternum; pilosity yellowish white, bases smaller than on scutum. Dense pilosity limited to patches on the posterior anepisternum, anepimeron, katepisternum, and katatergite, scattered pilosity on the katepimeron. Metasternum bare. Plumule yellow.

LEGS. Hind coxae without a distinct tuft of pile at posteromedian angle, but with scattered long, white pile; fore and mid coxae with shorter, yellow pile on anterior distal margins. Trochanters with scattered yellow pile. Fore and mid femur orange brown with small yellow-orange sections at the base and apex, hind femur orange brown, with yellow-white basal section and more orange ventrodistal section, fore femur curved, mid femur with a slight medial swelling, hind femur swollen in distal two thirds. Fore and mid femur with short yellow pile, hind femur mostly covered with short yellow pile, but with some brown pile in distal area (distal 1/7 dorsally, ⅓ ventrally). Fore tibia white in basal ½, brown in distal ½, mid tibia white in basal 3/5, orange brown distally, hind tibia brown. Pale sections of tibiae with short yellow-white pile, dark sections with short brown pile. Fore basitarsus brown, other fore tarsal segments brown dorsally but golden brown ventrally. Mid tarsus orange brown, slightly darker dorsally. Hind tarsus brown dorsally, orange brown ventrally. All tarsi with brown pile, somewhat darker dorsally than ventrally.

WINGS ( Fig. 12 ). Extensively microtrichose in apical part, bare patches at base of cells c, r 1, dm, and cup. Alula with bare central patch. Cell bm extensively bare, but with a small dense patch of microtrichia in the distal region, in line with the knot of the spurious vein. Cell br mostly bare, but with some microtrichia anterior to the knot of the spurious vein. Cell cua extensively bare, with some microtrichia centrally. Calypters white to yellow, darker dorsally, with fringe of long yellowish pile. Halteres yellow.

ABDOMEN ( Fig. 14 ). Elongate, broadly oval, though tergite 2 and tergite 3 parallel sided. Slightly shorter than the wings, about as wide as the thorax, basic colour dark brown with dull, orange yellow markings. Tergite 1 completely yellow; tergite 2 light basally, extending medially to form a large medial fascia with rounded posterolateral sides and a small medial point. Lateral margins of tergite 2 thinly yellow, joining with the main yellow marking anteriorly. Tergite 3 anterior with a broad anteromedial macula, about 4/5 of the length and ¾ of the width of tergite 3. Tergite 2 slightly longer than tergite 3, tergite 3 and tergite 4 the same length and tergite 5 about ½ the length of tergite 4. Pile short, light brown centrally and yellow laterally, somewhat longer lateral to tergite 1 and basolateral to tergite 3. Sternites 1–3 light yellowish brown, darker brown from sternite 4 onwards to the genitalia, pile mainly short, sparse yellowish, posterior edges of sternite 3–4 covered with sparse short brown pile.

MALE GENITALIA ( Figs 20–21 ). Large (1.1 mm long). Superior lobes projecting posteriorly about twice as long as surstyli, hatchet shaped in lateral view. Surstyli about 2.5 times as long as wide, rounded apically and covered in small hairs. Hypandrium shorter than superior lobes.

Female

As for male except as noted below:

HEAD ( Fig. 5 ). With medium sized frontal protuberance; widest just below the antennae, approximately 40% of the maximum head width, slightly narrowed ventrally, narrowest in line with dorsal oral margin, approximately 34% of maximum head width. Frons with dense yellowish-white pollinosity on the lower half, reaching from the frontal protuberance to the antennal prominence, the transition from pollinose to bare forming a straight or slightly convex line. Ommatidia equal across the eye.

THORAX ( Fig. 10 ). Scutellum slightly shorter than in male ~60% the width and ~40% the length of the scutum.

LEGS. Fore femur straight or only gently curved.

ABDOMEN ( Fig. 16 ). Broadly oval, only tergite 2 parallel sided. Slightly wider than thorax. Macula on tergite 3 narrower than in male, about ⅔ of the length of tergite 3. Tergite 2 1.5 times the length of tergite 3. Sternites all light yellowish brown, posterior edges of sternites 3–7 covered with sparse short brown pile.

Distribution

This species is known from the Cape Verde Islands, the Central African Republic, the Democratic Republic of the Congo, Ethiopia, Kenya, and the Republic of the Congo. Most of the habitat is Guineo-Congolian rainforest or forest remnants.

Remarks

The name “ congensis ” was used by Curran (1938) and is thus the correct spelling for this species. Kassebeer (2000b) introduced the incorrect spelling “ congoensis ” which has been used by other authors ( Goeldlin de Tiefenau & Thompson 2019; Mengual 2020), though not in formal taxonomic treatments. Due to the two spellings in use, care is needed to ensure all works referencing this species are used in future. In the description of X. magnificus ( Goeldlin de Tiefenau & Thompson 2019: figs 4–11), the figures of the genitalia show few differences from the drawings in Kassebeer (2000b: fig. 2a–e) or from our photographs ( Figs 19, 22 ). The only notable difference is the shape of the distal end of the postgonites in lateral view. If the postgonites of A. congensis are viewed from approximately 25° above the horizontal plane, the shape matches the figures in Goeldlin de Tiefenau & Thompson (2019). Based on the minimal differences in external and genital morphology between A. congensis and X. magnificus and the large observed interspecific differences in both external and genital morphology in Afroxanthandrus , we consider X. magnificus a junior synonym of A. congensis .

Xanthandrus magnificus was described from a type series of five specimens, all with identical label data. When the specimens were located at USNM, none bore type labels and six specimens with identical label data were found. As it is not possible to determine unequivocally which specimen is the holotype and which is not part of the type series, we consider all six specimens to be syntypes. Two of the six were separate, which we assume were meant as the two specimens to be returned to Lausanne. We designate the male of these as the lectotype and the female as a paralectotype. The four remaining specimens are designated as paralectotypes housed at USNM.

Goeldlin de Tiefenau & Thompson (2019) list the type locality for X. magnificus as “…the island of Sao Tome in the Sao Tome group off Gabon, Africa.” However, the label data for the series is “I Cap Vert, Sao Tome, 16 March 1977, J. Denon”. Given the convention of listing the country first on a label, followed by the nearest town or city, this likely refers to the town of São Tomé in the Praia Region on Santiago, Cape Verde Islands, and not the island of São Tomé, São Tomé and Príncipe.

Figures

Fig. 1. Map of the known distribution of species of Afroxanthandrus Kassebeer, 2000 in the Afrotropical region.

Figs 2–6. Frontal view of the head of species of Afroxanthandrus Kassebeer, 2000. 2. A. comorosensis sp. nov., holotype, ♂ (RMCA ENT 000056900). 3. A. congensis (Curran, 1938), ♂ (ANHRTUK 00282353). 4. A. conopeum sp. nov., holotype, ♂ (NMSA-Dip 219971). 5. A. congensis, ♀ (ANHRTUK 00282352). 6. A. longipilus Kassebeer, 2000, ♀ (ANHRTUK 00282356). Scale bars = 1 mm.

Figs 7–8. Lateral view of species of Afroxanthandrus Kassebeer, 2000. 7. A. comorosensis sp. nov., holotype, ♂ (RMCA ENT 000056900). 8. A. congensis (Curran, 1938), ♂ (ANHRTUK 00282353). Scale bars = 1 mm.

Figs 9–10. Lateral view of species of Afroxanthandrus Kassebeer, 2000. 9. A. conopeum sp. nov., holotype, ♂ (NMSA-Dip 219971). 10. A. congensis (Curran, 1938), ♀ (ANHRTUK 00282352). Scale bars = 1 mm.

Figs 11–12. Lateral view and wing of species of Afroxanthandrus Kassebeer, 2000. 11. A. longipilus Kassebeer, 2000, ♀ (ANHRTUK 00282356), lateral view. 12. A. congensis (Curran, 1938), ♂ (ANHRTUK 00282353), wing. Scale bars = 1 mm.

Figs 13–17. Dorsal view of the abdomen of species of Afroxanthandrus Kassebeer, 2000. 13. A. comorosensis sp. nov., holotype, ♂ (RMCA ENT 000056900). 14. A. congensis (Curran, 1938), ♂ (ANHRTUK 00282353).15. A. conopeumsp. nov., holotype, ♂ (NMSA-Dip 219971). 16. A. congensis, ♀ (ANHRTUK 00282352). 17. A. longipilus Kassebeer, 2000, ♀ (ANHRTUK 00282356). Scale bars = 1 mm.

Figs 18–23. Male genitalia of species of Afroxanthandrus Kassebeer, 2000. 18–20. Dorsal views. 18. A. comorosensis sp. nov., holotype (RMCA ENT 000056900). 19. A. congensis (Curran, 1938) (RMCA ENT 000028396). 20. A. conopeum sp. nov., paratype (NMSA-Dip 086809). 21–23. Lateral views. 21. A. comorosensis sp. nov., holotype (RMCA ENT 000056900). 22. A. congensis (RMCA ENT 000028396). 23. A. conopeum sp. nov., paratype (NMSA-Dip 086809). Scale bars = 0.5 mm.

Fig. 24. Neighbour-Joining tree generated from DNA barcode data for four species of Afroxanthandrus Kassebeer, 2000.