Revision of the Afrotropical species of the hover fly genus Mesembrius Rondani (Diptera, Syrphidae) using morphological and molecular data Author Jordaens, Kurt Royal Museum for Central Africa, Invertebrates Section and JEMU, Leuvensesteenweg 13, B- 3080 Tervuren, Belgium kurt.jordaens@africamuseum.be Author Goergen, Georg https://orcid.org/0000-0003-4496-0495 International Institute for Tropical Agriculture (IITA), Biodiversity Centre, 08 BP 0932 Tri Postal, Cotonou, Benin Author Skevington, Jeffrey H. https://orcid.org/0000-0002-1445-9870 Canadian National Collection of Insects, Arachnids and Nematodes, Agriculture and Agri-Food Canada, K. W. Neatby Building, 960 Carling Avenue, Ottawa, ON K 1 A 0 C 6, Canada Author Kelso, Scott Canadian National Collection of Insects, Arachnids and Nematodes, Agriculture and Agri-Food Canada, K. W. Neatby Building, 960 Carling Avenue, Ottawa, ON K 1 A 0 C 6, Canada Author Meyer, Marc De https://orcid.org/0000-0003-0755-2898 Royal Museum for Central Africa, Invertebrates Section and JEMU, Leuvensesteenweg 13, B- 3080 Tervuren, Belgium text ZooKeys 2021 2021-06-21 1046 1 141 http://dx.doi.org/10.3897/zookeys.1046.57052 journal article http://dx.doi.org/10.3897/zookeys.1046.57052 1313-2970-1046-1 66E61C4EFAFE45DE9145DB38199BDEC3 DBC42C98E4DA5074B86525CF2FB2FA64 Mesembrius arcuatus Jordaens, Goergen & De Meyer sp. nov. Figs 3 , 46 , 83 , 127 , 157 , 191 , 205 Differential diagnosis. The male of Mesembrius arcuatus sp. nov. is holoptic, has a profemur with a loose, black apical pile brush and a strongly curved metatibia which is dorsoventrally compressed in the middle third. It can be distinguished from any other species by the apical pile brush of the profemur which is loose and black dorsally and yellow ventrally (yellowish with some black pile interspersed in M. ingratus ; black in M. tarsatus ) and by the strongly compressed metatibia (with deep groove in M. ingratus ; with a rounded swelling in M. tarsatus ). The female is unknown. Examined material. Mesembrius arcuatus Jordaens, Goergen & De Meyer: Holotype , male, " HOLOTYPUS " " Entebbe , // Uganda .//21.8.11. // C.C. Gowdey. //1912-100." " Mesembrius arcuatus // Det. K. Jordaens , 2019" " NHMUK 010369965" [NHMUK]. Paratypes : Uganda • 1♂ ; Entebbe ; 11 Aug 1911 ; C.C. Gowdey leg.; NHMUK • 1♂ ; Entebbe ; 14 Aug 1911 ; C.C. Gowdey leg.; NHMUK • 2♂♂ ; Entebbe ; 14 Aug 1911 ; C.C. Gowdey leg.; NHMUK • 2♂♂ , Entebbe ; 16 Aug 1911 ; C.C. Gowdey leg.; NHMUK • 1♂ ; Entebbe ; 17 Aug 1911 ; C.C. Gowdey leg.; NHMUK • 3♂♂ ; Entebbe ; 21 Aug 1911 ; C.C. Gowdey leg.; NHMUK • 1♂ ; Entebbe ; 3-4 Dec 1912 ; C.C. Gowdey leg.; NHMUK • 1♂ ; Entebbe ; 13 Nov 1912 ; C.C. Gowdey leg.; NHMUK • 2♂♂ ; Entebbe ; 16 Oct 1912 ; C.C. Gowdey leg.; NHMUK • 5♂♂ ; Entebbe ; 1-11 Sep 1911 ; S.A. Neave leg.; NHMUK • 1♂ ; N.E. Side of Lake Albert ; 1906; A. Hodges leg.; NHMUK • 1♂ ; near Entebbe ; 5 Mar 1972 ; H. Falke leg.; CNC • 1♂ ; near Entebbe ; 1-14 Feb 1973 ; H. Falke leg.; CNC • 1♂ ;? Kanue ; 3 May 1911 ; collector unknown; NHMUK • 1♂ ; Mbarara ; 29 May 1911 ; collector unknown; NHMUK ; 1♂ ; Central Region , Wakisa District , Mabamba Swamps ; 16 Dec 2018 ; X. Mengual ; ZFMK • 2♂♂ , Central Region , Wakisa District , Mabamba Swamps ; 16 Dec 2018 ; M. Reemer leg.; RMNH • 1♂ ; Central Region , Wakisa District , Mabamba Swamps 1♂ ; 16 Dec 2018 ; K. Jordaens leg.; KMMA. Description male (Fig. 3 ). Body length: 13.7-14.2 mm. Wing length: 9.8-10.4 mm. Head (Fig. 46 ). Eyes bare; holoptic, length of eye contiguity equal to approx. the length of ocellar triangle. Face dark with dark medial vitta; white pilose; white pollinose. Vertical triangle black pilose; white pollinose in dorsal half. Ocellar triangle dark; black pilose; white pollinose; distance between lateral ocellus and eye margin 1/2 width of ocellus. Occiput yellow; white pilose; yellow and white pollinose. Frontal triangle orange-brown; white pilose. Frontal prominence shiny black; black pilose. Antenna dark brown to black; postpedicel white pollinose; antennal arista reddish-brown. Thorax . Scutum black with a pair of dorsal, well-demarcated grey pollinose vittae; yellow and black pilose. Scutellum uniformly light yellow-brown; yellow pilose throughout, black pilose on posterior 2/3. Legs . All femora and tibiae with long, loose, yellow pile and, especially at distal end, loose, black pile. Proleg (Fig. 157 ): Femur dark brown to black; with a loose, apical pile brush which is black pilose dorsally, yellow pilose ventrally; with long, yellow pile posterodorsally and with shorter, black pile anterodorsally and anteroventrally. Tibia with long, black pile, except dorsally. Basitarsus orange-brown; with long, black pile posteriorly. Other tarsi orange-brown; yellow and black pilose dorsally; orange pilose ventrally. Mesoleg: Dark brown to black, except for tarsi which are reddish-brown; black pilose dorsally, orange pilose ventrally. Metaleg (Fig. 191 ): Femur dark brown to black; very slender; covered with long, thin yellow pile, except on ventral side which is almost bare; with shorter, black pile on posteroventral proximal 2/3; with a series of thick, black setulae at distal 1/3; with thick, black pile at distal end. Tibia curved; strongly dorsoventrally compressed in middle 1/3; with long, yellow and black pile, except in the flattened posterior section. Tarsi yellow and black pilose, except ventrally where orange pilose. Wing (Fig. 127 ). Entire wing uniformly microtrichose. Abdomen (Fig. 83 ). Tergite II with a pair of very large, yellow triangular to rounded maculae; yellow pilose; black markings hourglass-shaped; posterior black marking equal in size or somewhat narrower than anterior black marking, with a medial white pollinose area; posterior black marking with black pile that posterolaterally extends into the yellow maculae. Tergite III with yellow-orange fascia and a large, black and strongly white pollinose triangular marking; pile short, stiff and black, except on the lateral sides where it is longer, thinner and yellow. Tergite IV strongly white pollinose anteriorly, with a large posterior, rounded, white pollinose black marking; pile short, thick and black, except on the lateral sides where it is longer, thinner and yellow. Genitalia (Fig. 205 ). Epandrium: Dorsal lobe of surstylus short and stout, with a very long, sharp expansion on distal end; short black spinose on apex and long brown pilose on dorsal surface. Ventral lobe of surstylus strongly convex; bare. Female. Unknown. Distribution. Uganda. Comments. This is a new species to the Afrotropical Region and only collected from Uganda. The female remains unknown, despite the fact that 28 males were collected or encountered in various collections. Etymology. The specific epithet Mesembrius arcuatus (Latin) means bent like a bow and was chosen with reference to the strongly curved metatibia. It is to be treated as an adjective (nominative singular masculine).