Meromacroides meromacriformis (Bezzi, 1915)

Bellingan, Terence, Midgley, John, Goergen, Georg & Jordaens, Kurt, 2021, Notes on the Afrotropical hover fly genus Meromacroides Curran (Syrphidae, Eristalinae), African Invertebrates 62 (2), pp. 383-397 : 383

Meromacroides meromacriformis (Bezzi, 1915)

Figs 1-2 , 3, 4 , 5, 6 , 7, 8 , 9-12 , 13-14

Eristalis meromacriformis Bezzi (1915), Syrph. Eth. Reg.: 93.

Meromacroides meromacriformis (Bezzi) - Curran (1927), Bull. Am. Mus. Nat. Hist. 57: 69 - Smith and Vockeroth (1980), Cat. Dipt. Afrotrop. Reg.: 503 - Dirickx (1998), Cat. Syn. Géogr. Syr. Rég. Afrotrop.: 81 - Whittington (2003), Stud. dipterol. 10: 595.

Differential diagnosis.

Meromacroides meromacriformis can be distinguished from any other hover fly species in the combination of the following characters: Postpronotum pilose; compound eye pilose; wing membrane microtrichose in apical 1∕3; wing vein R4+5 strongly sinuate; wing cell r1 closed and bulbous apically; thorax with triangular part of anepimeron and katepimeron weakly pubescent; metafemur greatly swollen.

Examined material.

Holotype: Male from South Africa (NHMUK). South Africa. • 1 ♂; “Holo-//type”. [printed, red border] " Eristalis //TYPE [printed]//meromacri//formis//Bezzi" [red border] " S. Africa //Plant//54. 83" " Eristalis // Eristalis meromacriformis //n. sp.//type ♂ " [all handwritten except as indicated]

While the holotype was described by Bezzi (1915) as "a single rather old and badly preserved specimen", it is still fully intact, albeit laden with dust and lint.

Other material.

Benin. • 1 ♀; Pobe Forest ; 6.963116, 2.674033; 10 Mar 2019; G. Goergen leg.; IITA . Democratic Republic Of The Congo. • 1 ♂; Mayumbe, Zobe ; Jan 1916; R. Mayné leg.; KMMA [RMCA ENT000040207] • 1 ♀; Stanleyville [=Kisangani]; Mar 1914; Lang-Chapin leg.; KMMA [RMCA ENT000034070] . • 1 ♂; Stanleyville [=Kisangani]; Apr 1915; Lang-Chapin leg.; AMNH . Mozambique. • 1 ♂; Inhambane Province, Inhambane; Jan 1924; R.F. Lawrence leg.; [SAM-DIP-A009617] . South Africa. • 1 ♂; KZN, Mtunzini, Raphia Palm Boardwalk ; -28.95764, 31.76136; 7 Nov 2020; J. Midgley, T. Bellingan leg.; [NMSA-DIP 205959] • 1 ♂; KZN, Mtunzini, Raphia Palm Boardwalk ; -28.95764, 31.76136; 4 Nov 2020; J. Midgley, T. Bellingan leg.; [NMSA-DIP 206113] . • 1 ♀; KZN, Mtunzini, Raphia Palm Boardwalk ; -28.95764, 31.76136; 13 Nov 2020; J. Midgley, T. Bellingan leg.; [NMSA-DIP 206122] . Togo. • 1 ♂; Kloto Forest ; Mar 2004; G. Goergen leg.; IITA [IITA DIP 00013902] • 1 ♂; Kloto Forest ; Apr 2004; G. Goergen leg.; IITA [IITA DIP 00013903] • 1 ♀; Kloto Forest ; Feb 2018; G. Goergen leg.; KMMA [RMCA_1088B03] • 1 ♂; Kloto Forest ; Feb 2018; G. Goergen leg.; KMMA [RMCA_1088B04] • 1 ♀; Kloto Forest ; Jan 2019; G. Goergen leg.; KMMA [RMCA_1224A02] • 3 ♂; Kloto Forest; Mar-Apr 2020; G. Goergen leg.; KMMA [RMCA ENT000033698 - 000033700] • 3 ♂; Kloto Forest; Mar-Apr 2020; G. Goergen leg.; IITA • 2 ♂; Kloto Forest ; Mar 2021; G. Goergen leg.; IITA .

Male

(Figs 1 , 3 , 5 , 7 - 12 ). Body length: 11.6-14.3 mm. Wing length: 8.0-9.6 mm.

Head (Fig. 3 ). Eye yellow-white pilose, pile length four times the diameter of ommatidium in South African and West African specimens, three times in Central African specimens; ommatidia equal in diameter across the eye; dichoptic, but distance between eyes varying from the width of 1-3 ommatidia (Fig. 3 ). Frons brown; more densely yellow pollinose anterior to ocellar triangle, less densely yellow pollinose on ocellar triangle and vertex; long yellow pilose. Frontal triangle dark brown, but orange-brown at antennal tubercle; strongly yellow pollinose; long yellow-white pilose. Face orange-brown; subshining; weakly yellow pollinose, but bare on facial tubercle; with strong yellow pollinosity at eye margin; yellow-white pilose, but pilosity much longer on gena than on other parts; facial tubercle orange-brown; strongly pronounced and bare. Occiput dark brown, covered with dull yellow to grey pollinosity; with dispersed pale pile and a few shorter, stiff black spines near eye margin around the head. Antennal segments brown, postpedicel rounded; length to height approx. 1.2; white pollinose; arista orange-brown, bare.

Thorax (Figs 1 , 5 ). Scutum sub-shining, reddish brown, dark brown to black, except postpronotum which is orange-brown; black punctuated; grey-white pollinose; with stronger pollinosity on anterior 1/5, along the transverse suture and at the posterior margin; pollinosity variable, appearing as two pollinose vittae fading at transverse suture in West African specimens, appearing as three darker pollinose vittae against a pale pollinose background in Central and South African specimens, with short yellow-white pile, at lateral margins somewhat longer. Scutellum dark brown, somewhat darker in anterior half; with even short black and yellow-white pile. Pleura ground colour red-brown to black-brown, except for anterior anepisternum where it is sometimes orange-brown; mostly even greyish pollinose, but anepisternum with reduced pollinosity anteriorly; covered with long pale pile on posterior anepisternum, katepisternum and anepimeron; very short white pubescence on other pleurites. Scutellum apical margin rounded, not marginated, 3 × as wide as long; subscutellum bare.

Legs (Figs 1 , 8 ). Proleg and mesoleg: Coxa orange-brown; white pollinose; with some long white pile anteroventrally. Trochanter orange-brown; white pollinose; with 7-8 short, light brown to black spines posteroventrally; with approx. 10 light brown to black spines on anterodistal end. Femur dark orange-brown; short white pilose; with very short black spines on dorso- and ventrodistal 2/3; with a patch of short black spines on anteroventral proximal end. Tibia dark brown to black; short white and black pilose. Tarsi dark brown to black dorsally, orange-brown ventrally; white pilose with some short, black spines on lateral sides. Metaleg: Coxa orange-brown; white pollinose; long white pilose anteroventrally. Trochanter orange-brown; white pollinose; with sparse yellow-white pile; with short, stiff black setulae ventrally. Femur strongly thickened, but markedly narrowed at distal end; at widest part as thick as approx. 1/4 of femur length; dark brown anteriorly, orange-brown posteriorly; short yellow-white pilose; with some very long white pile ventrally; with black setulae on ventrodistal 2/3 which are half the length of the sparse long white pile; with a patch of short black spines on anteroventral proximal end. Tibia slightly curved, but with a marked bend at proximal 1/8 dorsally; orange-brown but with a lighter ring in the middle; with a low carina on the entire anteroventral side; with a low carina from the distal end to the middle of the leg posteriorly; short yellow-white pilose; with some longer black hairs interspersed. Tarsi dark brown to black dorsally, orange-brown ventrally; white pilose with some black pile interspersed, especially ventrally.

Wing (Fig. 7 ). Entirely microtrichose; microtrichosity very dense on cells sc, r1, r2+3 and the dorsal distal half of cell r4+5. Cell r1 closed, bulbous apically, petiolate; vein R4+5 sinuate, not appendiculate; vein CuP bent. Spurious vein running deep into cell r4+5, approx. 2/3 of the way to vein M1. Calypters dark grey to yellow; with fringe of white to yellowish white pile. Halteres white to pale brown; light orange-brown proximally.

Abdomen (Fig. 5 ): Narrow, conical; tergite II trapezoid; be:tergite III rectangular, 1.1 to 1.4 × as long as wide; tergite IV rectangular, approx. 1.3 × as long as wide. Subshining dark brown to black-brown on dorsal side, more orange-brown on lateral sides; tergites II-III with yellowish white to orange-brown posterior border; post-abdomen more orange-brown; with greyish to greyish-brown pollinosity, except for post-abdomen; with short dark pile, except on anterolateral corners of tergite V where it is longer and on tergite I and lateral sides where it is longer and white. Sternites orange-brown to dark brown, with short dispersed pale pile and longer dispersed pale pile medially. Dispersed pale pollinosity on sternites II-IV, sternite I bare.

Genitalia (Figs 9-12 ). Cerci triangular, small; orange-brown; dorsally rounded in West African specimens (Fig. 12 ), but angular in South African specimens (Fig. 10 ); long yellow-white pilose. Epandrium large, elongated; broadly rounded at apex; dorsal and ventral margins straight and parallel in West African specimens (Fig. 11 ), rounded dorsally and not parallel in South African specimens (Fig. 9 ); ventrally expanded; with low ridge on inner side; with short, black spines on entire surface, but denser on inner low ridge; yellow-white pilose on dorsal half, black pilose on ventral half. Hypopygium small. Genitalia missing in Central African male specimen.

Female

(Figs 2 , 4 , 6 , 13 , 14 ). Body length: 12.9-15.5 mm. Wing length: 9.0-9.9 mm.

As male, except for the following characters:

Head (Fig. 4 ). Eyes broadly dichoptic. Ocellar triangle and vertex lighter yellow pollinose; frontal triangle with pilosity and pollinosity as in male, but absent near antennal tubercle. Face very weakly yellow pollinose; occiput with stiff black spines laterally near eye margin, but absent dorsally.

Thorax (Figs 2 , 6 ). Scutum with stronger pollinosity on anterior 3/5. Scutellum with pile longer and paler along the antero-lateral margins. Pleura whitish pollinose, but anepisternum bare anteriorly and with reduced pollinosity posteriorly, long pale pile longest in ventral region.

Legs (Fig. 2 ). Proleg and mesoleg: Coxa with pollinosity denser medially and anteriorly. Trochanter with 7-8 short, light brown spines posteroventrally. Femur orange-brown to dark brown; with short and medium length white pilosity, dorsal surface bare; with very short dark brown to black spines on dorso- and ventrodistal 2/3. Tibia dark brown fading to black towards distal end; with few stout black spines at posteroventral distal end. Metaleg: Trochanter with short, stiff, dark brown to black setulae ventrally. Femur with one row of pile along inner ventral surface of the femur and one row along outer ventral surface beginning at approx. the middle of the femur; with black setulae on ventrodistal 1/2-2/3 which are at least half the length of the sparse long white pile. Tibia orange-brown to dark brown becoming paler distally; short yellow-white to white pilose.

Abdomen (Fig. 6 ). Narrow, moderately conical; tergite II trapezoid, though not as markedly so as the male, comparatively slightly broader at distal end; tergite III rectangular, approx. 0.55 × as long as wide; tergite IV rectangular, approx. 1.75 × as wide as long. Tergite V triangular. Tergites II-III with light brown posterior border; post-abdomen similar light brown; with greyish brown or greyish yellow pollinosity; with short pile that may be light or dark, except on anterolateral corners of tergite V where it is longer and on tergite I and lateral sides where it is longer and lighter in colour.

Geographic variation.

Male and female specimens from Western, Central and Southern Africa differ in subtle characters (summarised in Table 2 ). In general appearance, male specimens from Southern and Central Africa are larger than the West African specimens examined and more evenly and paler brown in ground colour. The contrast between light and dark parts of the body is less distinct than specimens from West Africa. The holotype does not differ from the recent Southern African specimens.

DNA barcodes.

Table 1 contains GenBank accession numbers and institutional catalogue numbers for the five M. meromacriformis specimens barcoded. The mean p-distance in the DNA barcode region between specimens from Togo and from South Africa is 0.019 (or 1.9%).

Distribution.

(Based on material examined, except as noted) Benin, Democratic Republic of the Congo ( Curran 1927), Kenya ( De Meyer et al. 1995), Mozambique, South Africa (also Bezzi 1915; Smith and Vockeroth 1980), Togo, Uganda ( De Meyer et al. 1995; Smith and Vockeroth 1980).

Comments.

The collector, RW Plant, moved to South Africa in 1850 and died on an expedition in 1858. During his time in South Africa, he lived in KwaZulu-Natal and there is no record of his travelling to other parts of South Africa. The only collecting trip he undertook that produced appreciable specimens was in 1858, to northern KwaZulu-Natal. The exact route of the expedition is unknown ( McCracken 2011). Plant’s diary was lodged at the Killie Campbell Library ( Glen and Germishuizen 2010), but is now missing. The type data can be narrowed to the KwaZulu-Natal province between 1850 and 1858.

Biological observations.

We observed two males and a female hovering inside a rot-hole in a single Voacanga thouarsii Roem. and Schult. ( Apocynaceae ) tree filled with termite frass ( Termitidae : Termitinae : Amitermes ?) and other biological material (Mtunzini, KwaZulu-Natal, South Africa) (Figs 13-15 ). The observations were made on three different days (4 Nov 2020; 7 Nov 2020; 13 Nov 2020) and no mating was observed. Only the female was observed alighting on the substrate (Fig. 14 ). The habitat is a modified Swamp Forest FOa2 ( Mucina and Rutherford 2006) with an artificially high number of Raphia australis Oberm. & Strey. palms.

Figures

Figures 1, 2. Meromacroides meromacriformis (Bezzi, 1915), habitus, lateral view 1 male specimen, South Africa (NMSA-DIP 206113) 2 female specimen, South Africa (NMSA-DIP 206122).

Figures 3, 4. Meromacroides meromacriformis (Bezzi, 1915), frontal view 3 male specimen, South Africa (NMSA-DIP 206113) 4 female specimen, South Africa (NMSA-DIP 206122).

Figures 5, 6. Meromacroides meromacriformis (Bezzi, 1915), dorsal view 5 male specimen, South Africa (NMSA-DIP 206113) 6 female specimen, South Africa (NMSA-DIP 206122).

Figures 7, 8. Meromacroides meromacriformis (Bezzi, 1915), wing and metaleg 7 left wing, male specimen, South Africa (NMSA-DIP 206113) 8 metaleg lateral view, male specimen, idem.

Figures 9 - 12. Meromacroides meromacriformis (Bezzi, 1915), male terminalia 9, 11 ventral view 10, 12 lateral view 9, 10 male terminalia from specimens from South Africa (NMSA-DIP 205959) 11, 12 male terminalia from specimens from Togo (RMCA-ENT 000033698).

Figures 13 - 15. A female Meromacroides meromacriformis (Bezzi, 1915) live pictures 13 female hovering above a rot-hole in the stem of a Voacanga thouarsii (Apocynaceae) tree at Mtunzini, KwaZulu-Natal (South Africa) 14 female alighted in a rot-hole, idem 15 relative size of the rot-hole illustrated with a 30 cm steel ruler, idem.