Mesembrius sulcus Jordaens, Goergen & De Meyer, 2021

Jordaens, Kurt, Goergen, Georg, Skevington, Jeffrey H., Kelso, Scott & Meyer, Marc De, 2021, Revision of the Afrotropical species of the hover fly genus Mesembrius Rondani (Diptera, Syrphidae) using morphological and molecular data, ZooKeys 1046, pp. 1-141 : 1

publication ID	https://dx.doi.org/10.3897/zookeys.1046.57052
publication LSID	lsid:zoobank.org:pub:66E61C4E-FAFE-45DE-9145-DB38199BDEC3
persistent identifier	https://treatment.plazi.org/id/AD9517F7-E4CA-479A-BC44-B7B9401C1313
taxon LSID	lsid:zoobank.org:act:AD9517F7-E4CA-479A-BC44-B7B9401C1313
treatment provided by	ZooKeys by Pensoft
scientific name	Mesembrius sulcus Jordaens, Goergen & De Meyer
status	sp. nov.

Treatment

Mesembrius sulcus Jordaens, Goergen & De Meyer sp. nov. Figs 23 View Figures 23, 24 , 43 View Figures 43, 44 , 66 View Figures 64–69 , 80 View Figures 79–82 , 103 View Figures 101–106 , 124 View Figures 124–126 , 147 View Figures 147–150 , 155, 164 View Figures 163–165 , 176 View Figures 172–176 , 187 View Figures 185–188 , 225 View Figures 217–228

Differential diagnosis.

Mesembrius sulcus sp. nov. males have an apical pile brush on the profemur of thick and dense black pile dorsally and yellow pile ventrally. The metafemur is very long and slender and has long yellow pile throughout and shorter, yellow and black pile on the ventral side. The metatibia has a deep groove on the posterior proximal half which is bordered by long black pile. The probasitarsus has a tuft of long black pile on the posterior side. The male differs from any other species in the colour of the apical pile brush (except from M. tibialis sp. nov.) which is black dorsally and golden-yellow ventrally (yellow-orange in M. chapini ; dark-brown to black in other species). It differs from M. tibialis sp. nov. in the entirely orange probasitarsus (orange and black in M Mesembrius tibialis sp. nov.), in the presence of a deep groove in the posterior proximal half of the metatibia (absent in M. tibialis sp. nov.) and in the unmodified mesotibia (proximal half strongly compressed in M. tibialis sp. nov.). Females have a frons which is black pilose on its entire length, except laterally. It can be distinguished from other such females (except from M. tarsatus ) by the black legs, including the tibiae (tibiae yellow-brown in other species). It differs from the female of M. tarsatus in tergite II, which has a pair of small yellow-orange maculae that laterally reach to halfway of the tergite length (almost to posterior end in M. tarsatus ) and in tergite III which has a pair of vague anterolateral yellow-orange maculae (clear pair of maculae in M. tarsatus ).

Examined material.

Mesembrius sulcus Jordaens, Goergen & De Meyer: Holotype, male, “HOLOTYPUS” “MUSÉE DU CONGO // Ituri : Nioka // - VII-1934 // J. Leroy " " van Doesburg det., 1956 // Mesembrius // spec.?nov. ♂ " "RMCA ENT // 000030186" [KMMA].

Paratypes: Malawi • 1♂; Mount Mulanje; 17 Oct 1913; S.A. Neave leg.; NHMUK 013428977 • 1♂; Zomba; Feb 1911; J.E.G. Old. Leg.; NHMUK • 2♂♂; Mount Mulanje; 17 Oct 1913; S.A. Neave leg.; NHMUK . Kenya • 3♂♂ 3♀♀; Nairobi, Karura Forest ; 2 Dec 2017; K. Jordaens leg.; ICIPE . South Africa • 1♂; Port St. Johns ; 1-31 Oct 1969; E. and W. Gess leg.; AMGS .

Description male

(Fig. 23 View Figures 23, 24 ). Body length: 14.0-15.6 mm. Wing length: 10.2-11.5 mm

Head (Fig. 66 View Figures 64–69 ). Eyes bare; holoptic, eye contiguity approx. as long as length of ocellar triangle. Face yellow to orange with dark medial vitta; white pilose; white pollinose. Vertical triangle black; black pilose; yellow pollinose on medium third. Distance between lateral ocellus and eye margin slightly less than width of ocellus. Occiput yellow; yellow pilose with some shorter and thicker black pile near eye margin; yellow and white pollinose. Frontal triangle short; yellow-white; with some long, yellow and black pile; white pollinose. Frontal prominence shiny black with orange-brown apex. Antenna, scape and pedicel reddish-brown; postpedicel black, white pollinose; antennal arista reddish-brown.

Thorax. Scutum black with dorsally a pair of very faint white pollinose vittae; lateral white pollinose vitta very faint; yellow pilose. Scutellum uniformly yellow-brown; long yellow pilose with some very short black pile on posterior half.

Legs. All legs chocolate-brown to black, but protarsus orange. Proleg (Figs 155, 164 View Figures 163–165 ): Femur dorsoventrally flattened; with long yellow pile posterodorsally; with apical pile brush of thick black pile dorsally and thick yellow pile ventrally; with short and black thick pile at proximal end. Basitarsus orange; with a tuft of black pile posteriorly. Other tarsi orange; with sparse short black pile. Mesoleg (Fig. 176 View Figures 172–176 ): Femur, ventrally with long yellow pile on proximal 2/3 and shorter black pile on distal 1/3, with some long black pile interspersed in middle section. Metaleg (Fig. 187 View Figures 185–188 ): Femur long and thin, slightly curved; with yellow pile anterodorsally; with some denser shorter and black pile at distal ventral end. Tibia with long black pile; posteriorly with deep and broad excavation in proximal half which is bordered with long black pile.

Wing (Fig. 147 View Figures 147–150 ). Entire wing uniformly dense microtrichose.

Abdomen (Fig. 103 View Figures 101–106 ). Tergite II with a pair of very large, yellow, more or less triangular maculae; black marking hourglass-shaped; posterior and anterior black marking slightly connected in the middle; posterior marking with strong white pollinosity; yellow pilose, except for black pile at posterior border of posterior black marking. Tergite III and IV with orange fascia; black marking on posterior half strong white pollinose; black pilose in medial part of black marking, yellow pilose on orange fascia and lateral parts of black marking.

Genitalia (Fig. 225 View Figures 217–228 ). Epandrium: Dorsal lobe of surstylus broadly rounded; with short black spines on almost entire surface; dorsally long yellow pilose. Ventral lobe of surstylus straight; bare.

Description female

(Fig. 43 View Figures 43, 44 ). Body length: 11.2-13.4 mm. Wing length: 12.7-16.6 mm.

Head (Fig. 80 View Figures 79–82 ). Eyes bare; dichoptic. Face white with dark medial vitta; white pilose; white pollinose. Frons black; black pilose in dorsal half and medial ventral half, yellow pilose on lateral sides of ventral half; yellow-white pollinose, especially in ventral half. Distance between lateral ocellus and eye margin 1½× width of ocellus. Occiput black; yellow pilose, with some black pile near eye margin; yellow-white pollinose. Frontal prominence shiny black. Antenna, scape and pedicel orange-brown; postpedicel black; antennal arista reddish-brown.

Thorax. Scutum dark brown to black with dorsally a pair of vague brown pollinose vittae which are connected posteriorly; yellow pilose with some black pile interspersed. Scutellum dark brown with lighter posterior border; yellow pilose.

Legs. All femora, tibiae and metatarsi dark brown to black, except for extreme distal ends which are reddish-brown (as in M. tarsatus ; Fig. 168 View Figures 166–171 ); yellow pilose; metatibia with short black spines on posteroventral 1/3. Pro- and mesotarsi orange; most distal tarsomere darkened distally, sometimes all tarsi darkened; dorsally short black pilose, ventrally short yellow pilose.

Wing. Entire wing uniformly dense microtrichose.

Abdomen (Fig. 124 View Figures 124–126 ). Tergite II black; yellow pilose with some very short thick black pile on black markings; with a pair of L-shaped, small orange maculae; white pollinose, especially in the central area of the posterior black marking. Tergite III black; yellow pilose with short thick black pile interspersed, especially in the posterior half; with a pair of small orange maculae in the anterolateral corners. Tergite IV as tergite III, but without orange maculae. Tergite V black; yellow pilose.

Distribution.

Democratic Republic of the Congo, Kenya, Malawi and South Africa.

Comments.

This is a new species to the Afrotropical Region with a relatively wide distribution. The species morphologically resembles M. tarsatus , which appears to be its sister species (see Fig. 230 View Figure 230 ), but the males differ markedly in the morphology of the metafemur. Females are very similar to females of M. tarsatus . The mean p -distance for the DNA barcoding is relatively low (1.6 %), but differences are consistent (i.e. no barcodes are shared between the species) (Fig. 229 View Figure 229 ).

Etymology.

The specific epithet Mesembrius sulcus (Latin) means groove (noun in apposition) and was chosen with reference to the deep groove on the metatibia. It is to be treated as an adjective (nominative singular masculine).