Taxonomic revision of the Afrotropical hover fly genus Senaspis Macquart (Diptera, Syrphidae)

Abstract The representatives of the Afrotropical hover fly genus Senaspis Macquart (Diptera) are revised. In total, ten species are recognized. Senaspis apophysata (Bezzi) is herewith placed as junior synonym of S. flaviceps Macquart, S. livida (Bezzi) is herewith placed as junior synonym of S. dentipes (Macquart) and S. griseifacies (Bezzi) is herewith placed as junior synonym of S. haemorrhoa (Gerstaecker). All species are redescribed and an identification key is provided. DNA barcoding analysis (7 species, 64 barcodes) showed that the technique can be used to unambiguously identify the species. The relationships among the different Senaspis species are discussed based on morphological and DNA data.


Introduction
Hover flies (Diptera, Syrphidae) constitute a diverse family of true flies, comprising ca. 6200 species (Pape et al. 2013). The group is poorly represented in the Afrotropical Region with slightly over 600 species known (Ssymank et al. in press). However, this could be a reflection of the limited surveying and studies conducted on this group in the region (Dirickx 1998). Nevertheless, syrphids most likely play an equally important role as pollinators, predators or decomposers, in a number of ecosystem services, as they do in other biogeographical regions (Inouye et al. 2015). Reviews on the current state are provided by Dirickx (1998), Whittington (2003) and Ssymank et al. (in press) and there is a clear need to improve the general knowledge on this group of flies.
Among the elements hampering an improved knowledge of the Afrotropical syrphid diversity is the lack of identification tools for most genera (Ssymank et al. in press). Eristalines are not an exception to this with relatively recent keys (i.e., published over the last 30 years) available only for the genera Ceriana Rafinesque, 1815 (Thompson 2013), Chasmomma Bezzi, 1915(Kassebeer 2000, Graptomyza Wiedemann, 1820 (Whittington 1992(Whittington , 1994, Megatrigon Johnson, 1898 (Doczkal et al. 2016), Syritta Le Peletier & Audinet-Serville, 1828 (Lyneborg and Barkemeyer 2005) and Phytomia Guérin-Méneville, 1834 (De Meyer et al. 2020). Currently, the African fauna of a number of eristaline genera is under revision, aiming to improve our knowledge for this group. This paper presents a taxonomic revision for the Afrotropical representatives of the genus Senaspis Macquart, 1850.
Senaspis was described by Macquart in 1850 with type species Senaspis flaviceps Macquart, 1850. It is an exclusively Afrotropical genus, although the types of some species were labelled as originating from the Neotropical (S. nigripennis (Macquart, 1855), Colombia) or Oriental (S. dentipes (Macquart, 1842), Java) Regions (see below under comments under respective species for details). Kertész (1910) made the unjustified emendation of the genus name to Stenaspis. As the latter is pre-occupied by Stenaspis Audinet-Serville, 1834 (Coleoptera: Cerambycidae), Bezzi (1912) proposed Protylocera Bezzi, 1912 as new name. However, Curran (1927a) outlined that the initial change to Stenaspis was unnecessary and thus the name Senaspis is retained as valid. Loew (1860) suggested using the name Plagiocera Macquart, 1842 for S. maculipennis (Loew, 1858) and related species, which Loew did not list. The genus Plagiocera was proposed by Macquart (1842) for the Nearctic Milesia cruciger Wiedemann, 1830. However, the name is preoccupied by Plagiocera Klug, 1834 (Hymenoptera: Cimbicidae) (see Evenhuis et al. 2016). Hull (1949) proposed the name Triatylosus Hull, 1949 as subgenus for a single species with additional facial tubercles on either side of the medial one: Xylota dibaphus Walker, 1849. This subgeneric division was not followed by Smith and Vockeroth (1980) in the Catalogue of Afrotropical Diptera. The latter listed 14 Senaspis species, but they recorded Eristalis cupreus Macquart, 1842both under Senaspis and under Eristalinus Rondani, 1845. Whittington (1993 listed it solely under the genus Senaspis. Dirickx (1998) listed cupreus Macquart under the genus Eristalis Latreille, 1804. The study of the type material of this species (at MNHN) corroborates that it is not a Senaspis species but a species of the genus Eristalinus sensu stricto and thus, it is excluded from this revision.
Representatives of Senaspis are reported from wetlands and riverbanks, especially when visited by domestic or wild mammals, as well as other water bodies (Ssymank et al. in press). Several specimen labels indicate rotting stems of banana stumps or decaying coconut trunk (Harmer 1913) as larval habitat and Copeland et al. (1999) described the larvae of S. haemorrhoa (Gerstaecker, 1871) collected from a stump of the cycad Encephalartos tegulaneus Melville (Zamiaceae). Furthermore, larvae of Senaspis species have been reported from sewage ponds and pig slurry (Curtis and Hawkins 1982;Ssymank et al. in press). Though adult Syrphidae are likely among the most important pollinators within the Diptera (Doyle et al. 2020), literature records of flower visiting Senaspis are still scanty (Nilsson et al. 1986) probably due to the unavailability of comprehensive identification keys for the genus.
Recent expeditions by staff members of the Royal Museum for Central Africa and the International Institute of Tropical Agriculture, as well as specimens collected independently by other research groups, have expanded the material available, including specimens suitable for DNA extraction. The main objectives of this manuscript are, therefore, to provide a taxonomic revision of all representatives of the genus Senaspis, to present an identification key and to discuss the interrelationships based on morphological and DNA data.
Morphological terminology largely followed Thompson (1999). Morphological observations were made with a Leica MZ8 stereomicroscope. Digitial images were obtained using the set-up as outlined in Brecko et al. (2014). Stacking was done using the software Zerene Stacker (zerenesystems.com/cms/home). Male genitalia were dissected using forceps and soaked 24-48 hours (depending on time required for sufficient clearance) in a cold 10% KOH solution after which they were transferred to acetic acid for 24 hours. Once sufficiently cleared, they were transferred to glycerine. Digital images were taken with a Leica MZ16 microscope and mounted Leica DFC500 digital camera using Leica Application Suite (LAS) automontage software (version 3.8). Measurements of wing and body lengths were taken by use of a calibrated ocular through the stereomicroscope, and are based on ten specimens (whenever available) randomly chosen, from which minimum and maximum length were selected. Body measurements were taken between the anterior margin of the frons and the posterior end of tergum IV; wing measurements between the tegula and the apex of the wing. For type material, text on identification and location labels is given ad verbatim. Text is indicated in quotation marks (" ") and each line on the label is separated by a double forward slash (//). Text not given on labels (i.e., collection depository) is given in square brackets ([ ]).
Literature references are given for original taxon descriptions under each species. For full bibliographic references, we refer to Dirickx (1998).
Procedures for DNA barcoding followed Jordaens et al. (2015). Briefly, genomic DNA was extracted from a single leg using the NucleoSpin Tissue Kit (Macherey-Nagel, Düren), following the manufacturer's instructions. PCR reactions were undertaken in 25 µl reaction volumes that contained 1.5 mM MgCl 2 in 1 × PCR buffer (Invitrogen), 0.2 mM of each dNTP, 0.2 µM of each primer and 0.5 units of Taq polymerase (Invitrogen). The DNA barcode fragment of the mitochondrial cytochrome c oxidase subunit I (COI) gene was amplified using primer pair LCO1490 and HCO2198 (Folmer et al. 1994). The PCR profile was an initial denaturation step of 5 min at 95 °C, followed by 35 cycles of 45 s at 95 °C, 45 s at an annealing temperature of 45 °C and 1.5 min at 72 °C, and ending with a final extension step of 5 min at 72 °C. PCR products were purified using the GFX PCR DNA Purification Kit (GE Healthcare) and diluted in 15 µl of sterile water or using the ExoSap protocol (Invitrogen) following the manufacturer's instructions. PCR-products were bidirectionally sequenced using the ABI PRISM BigDye Terminator v3.1 Cycle Sequencing Kit and run on an ABI3130xl Genetic Analyzer. Sequences were assembled in SeqScape v2.5 (Life Technologies) and inconsistencies were checked by eye on the chromatogram.
A Neighbor-Joining (NJ) tree (Saitou and Nei 1987) was constructed using the K2P model in MEGA v7 (Kumar et al. 2016) (see Suppl. material 1: Fig. S1), and pairwise p-distances (i.e., the proportion of sites at which two sequences differ) within and among species were calculated. Moreover, a NJ and a Maximum Likelihood (ML) topology (Guindon and Gascuel 2003) were constructed after removing identical sequences with DAMBE v.7 (Xia 2018) (Fig. 114). Branch support in the NJ analysis was evaluated using 1,000 bootstrap replicates. For the ML analysis, the dataset was partitioned according to codon position and the Akaike Information criterion in jModelTest v.2 (Guindon and Gascuel 2003;Darriba et al. 2012) was used to select the most appropriate model of evolution. These were the F81+I+G (first position), GTR+I+G (second position), and GTR+G (third position) model, respectively. Then, Garli v.2.01 (Zwickl 2006) was used to perform the ML analysis (two replicates; 500 bootstrap pseudoreplicates) taken into account the most appropriate models of evolution for each of the three codon positions. In each analysis, Eristalis tenax was constrained as root. Bootstrap values were considered to be meaningful if ≥ 70% (Hillis and Bull 1993). Specific results of the DNA barcode analysis are discussed in the Comments parts under each taxon of the Taxonomy and systematics section when relevant and in the Discussion.
Generic diagnosis. Senaspis species are morphologically characterized by the combination of the following characters: eyes bare and maculate (less conspicuous in dried specimens), dorsal facets in male usually only slightly larger than ventral facets, more pronounced so in S. dibapha (Walker, 1849) and S. nigrita (Bigot, 1859) Postabdomen (terga posterior to tergum IV) and at least part of tergum IV conspicuously orange to orange-red, with pale orange pile (Fig. 95), sometimes all abdominal terga largely yellow to yellow-orange (Fig. 100). Metafemur with two ventral swellings on apical part, the proximal swelling less developed (Fig. 85)
Legs. Brown to black-brown; with short black pile, along posterior margin of proand mesofemora with longer pale pile. Metafemur (Fig. 80) distinctly thickened, with one distinct ventral swelling in apical fifth, with dense short stout setae on swelling; metatibia thickened and slightly curved, with pile along ventral margin not distinctly more dense.
Wing (Fig. 64). Faint yellowish brown tinge, towards posterior margin and apex more greyish; with distinct dark brown macula running from anterior margin and covering most of stigma, parts of cell r 1 and r 2+3 , distal part of cell br and basal part of r 4+5 , decreasing in colour on anterior part of cell dm; distally of brown macula more hyaline patch. Calypters yellow-white, in medial part more pale brownish; with fringe of yellow-white pile. Cell r 1 variable, usually closed with petiole at most equal to height of base of stigma but usually shorter, sometimes closed but petiole missing; vein R 4+5 sinuate, usually not appendiculate, rarely with short appendix. Abdomen (Fig. 91). Subshiny brown to black-brown, postabdomen more reddish brown; with greyish to greyish brown pollinosity, except for anteromedial macula on terga I and II, pair of sublateral maculae on terga I-III and posterior part of tergum IV where more shining; with short dark pile, except tergum I, anterior margin tergum II, and lateral margins of all terga where pale pile. Sterna orange-brown to black-brown, with short dispersed pale pile. Male genitalia as in Fig. 102.
Female. As male except for the following character states: Eye (Figs 14, 15) dichoptic, facets equal to subequal in size. Frons subshiny black to black-brown in ventral protruding part, dorsally with greyish to greyish brown pollinosity. Postabdominal terga often less reddish brown; subshiny maculae sometimes more extensive and more pronounced.
Distribution. Angola, Benin, Burundi, Cameroon, Democratic Republic of the Congo, Equatorial Guinea, Ethiopia, Gabon, Ghana, Guinea Bissau, Ivory Coast, Kenya, Liberia, Malawi, Mozambique, Nigeria, Republic of the Congo, Sierra Leone, South Africa, Tanzania, Togo, Uganda, Zimbabwe. 'Java' as type locality is probably an error.
Comments. The orginal description of dentipes Macquart mentioned the geographic origin of the type as "de Java". No label on the lectotype pin indicates a locality or region, and the locality is probably an error. The type specimen of dentipes bears a lectotype label with designation by F.C. Thompson in 1977. The original description did not indicate the number of specimens examined by Macquart but only made reference to the fact that the description is based on male only and that material is housed in the 'Muséum' (referring to MNHN). No additional specimens could be traced in the MNHN collection. The lectotype designation (made in accordance with recommendation 73♀ of the ICZN (Thompson pers. comm.)) has not been published elsewhere.
The type of maculipennis Loew could not be traced. According to the original description (Loew 1858) as well as the detailed redescription by Loew (1860), this is a male specimen from 'Guinea'. One female specimen in MNB collection (Guinea, Westerm., additional label '843') is indicated as type but this contradicts with the above, and thus appears not be part of the type series. This specimen was also mentioned by Karsch (1887). According to Smith and Vockeroth (1980) 'Guinea' refers to Guinea Bissau.
The taxon livida Bezzi was described as a variety of aesacus Walker by Bezzi (1912), based on two specimens from Fernando Po [= Bioko Island], which were among a series of specimens identified as aesacus. He pointed out the few morphological differences and suggested that they could be just teneral specimens, which did not attain their full colours and wing markings. Smith and Vockeroth (1980) elevated livida to species rank. Examination of the type material, however, indicates that Bezzi was correct in considering these as teneral specimens and that there is no morphological evidence for considering livida as a distinct species, different from dentipes. We, therefore, synonymize livida with dentipes.
Thorax (Fig. 53). Scutum subshiny black; with very short black pile; postpronotum and notopleuron more orange to rufous and with longer pale or dark pile; trans- verse suture with fascia of black pollinosity. Scutellum clearly marginated, distinctly rounded and at most twice as wide as long; rufous, sometimes darker; with short dark pile, along margins paler pile. Pleura ground colour black to black-brown, along anterior spiracle more orange to rufous, covered with dispersed long dark pile except on meron, dorsomedial anepimeron, ventral part of katepimeron, anterior part of katepisternum and anterior anepisternum.
Legs. Orange to rufous (very rarely more brown), metatarsomeres 3-5 darker; with short pale orange pile, along posterior margin of pro-and mesofemora and ventral margin of metafemur with longer pile, sometimes pile partially dark red. Metaleg (Fig. 81), femur slender, with slight ventral swelling in apical fifth, pile at swelling black and more dense; tibia slightly thickened and curved, pile along ventral margin in apical half to two-thirds longer and more dense.
Wing (Fig. 65). Brownish, except alula and along posterior margin where hyaline; hyaline area not distinctly demarcated. Calypters dull chalk-white to yellow with fringe of silvery white to yellow pile (Figs 66, 67). Cell r 1 closed, petiole usually shorter than height of base of stigma, at most as long as base. Vein R 4+5 sinuate and short appendiculate, sometimes appendix missing. Abdomen (Fig. 92). Uniformly subshiny black to black-brown, rarely posteriorly more rufous; with short dark pile except tergum I where silver-grey. Sterna rufous to black-brown; with dispersed long pale pile except for sternum IV and postabdomen where dark. Male genitalia as in Fig. 103.
Female. As male except for the following character states: Eye dichoptic (Figs 18, 19), dorsal facets slightly larger than ventral ones. Frons with rufous to black pollinosity in dorsal part for length equal to ocellar triangle; with short dark pile except dorsal of antennal implant where intermixed with greyish pile. Scutellum usually darker, almost concolourous with medial part of scutum, sometimes more than twice as wide as long.
Distribution. Angola, Benin, Burundi, Cameroon, Central African Republic, Democratic Republic of the Congo, Equatorial Guinea, Gabon, Ghana, Guinea Conakry, Ivory Coast, Kenya, Liberia, Malawi, Mozambique, Nigeria, Republic of the Congo, Rwanda, Sierra Leone, Tanzania, Togo, Uganda, Zimbabwe. Record from Colombia for the type specimen of nigripennis is probably an error as the species is not reported from the Neotropical Region (see Comments).
Comments. This species has been described under several names but most of them were synonymized subsequently. No distinct character states could be discerned to confirm the specific status of these taxa, so the different synonymies are confirmed. The description of S. nigripennis deviates in some aspects from the morphological character states observed in S. dibapha: "face d'un noir brunâtre luisant" [face shiny brownish black]; "Thorax et abdomen… à légers reflets verts" [Thorax and abdomen with light greenish reflections]; "jambes postérieures…. ciliées de noir" [posterior legs… black ciliated]. Other character states correspond with S. dibapha. However, the two syntypes of S. nigripennis in the NHMUK collection do not correspond with the above mentioned deviations, although one syntype (partially covered in mould) does have a darker facial colour than usually observed and the pilosity of the metatibia is dark reddish (as observed in other specimens). Speiser (1913) also pointed out a slightly different shape of the scutellum in S. nigripennis, compared to S. dibapha, but this seems to fall within the variability observed in the material examined. In all other aspects they are identical to other material of S. dibapha studied, including the type. They are labelled as originating from Colombia, as stated in the original description by Macquart: "De la Colombie". Speiser (1913) already suggested the synonymy, but he did not formally designate it based on the geographical issue. Thompson et al. (1976) in the Neotropical catalogue listed this under the genus Palpada Macquart, 1834 as a new combination and indicated Oxford museum as type depository. However, no type specimen could be traced in the OXUM collection (Z. Simmons, pers. comm.). Montoya (2016) did not list nigripennis anymore in his catalogue of Syrphidae from Colombia. The Systema Dipterorum website (Evenhuis and Pape 2020) listed it as junior synonym of S. dibapha. We consider the type material at NHM as being representative and hence S. nigripennis as being synonymous with S. dibapha. The type of S. dibapha bears a lectotype label by F.C. Thompson, dated 1987, but this lectotype designation does not seem to have been published. Here we thus formally place nigripennis Macquart as synonym of dibapha Walker. Speiser (1910) described gypseisquama from a number of specimens originating from West (Cameroon and Sierra Leone) and East (Tanzania, Uganda) Africa. Afterwards, Speiser (1911) considered the material from West Africa as a separate variety (sulfurata), based on the coloration of the calypters. Of the specimens from West Africa, a number could be traced in the MNB collection (see above type material examined). The material from Uganda (for gypseisquama) and part of the material from Barombi, Cameroon and the male specimen from Kondué, Democratic Republic of the Congo (for var. sulfurata) could, however, not be traced. The female specimen from Sierra Leone in the MNB collection (apparently received or purchased from Staudinger) could be the type referred to as 'ein angekauftes F aus Sierra Leone' in Speiser (1910). Although the latter is not explicitly mentioned in Speiser (1911) as type of var. sulfurata, it is implied under "Alle diese Exemplare haben hell citronengelbe statt weisser Schüppchen, sind aber sonst völlig gleich mit den Ostafrikanern" [All of these specimens have bright lemon yellow instead of white calypters, but are otherwise identical to the East Africans] (in Speiser 1910) and "westafrikanische Form als besondere Varietät mit einem Namen zu belegen" [to assign a name to the West African form as a special variety] (in Speiser 1911). Smith and Vockeroth (1980) listed sulfurata as a distinct species but as junior synonym of dibapha. As indicated the colour of the lower calypter is variable from yellowish to bright white. Speiser (1911) suggested that there is a geographical separation between S. gypseisquama sensu stricto found in eastern Africa, and the variety sulfurata found in West and Central Africa. However, we have studied long series throughout the full geographical range and do not confirm this pattern. Both colour forms were found in close by or same locations (Figs 66, 67, material from same locality in the Democratic Republic of the Congo: Dekese, Itunda). DNA barcodes of specimens from West (i.e., Benin, Ghana, Togo), Central (D.R. Congo) and East (Uganda) Africa do not show any separation (Suppl. material 1: Fig. S1). No other correlated characters states could be linked to the color of the lower calypter. Therefore, the character is considered to be variable, not related to geographic distribution and of no taxonomic importance. Austen, 1909 Figs 3, 20-23, 54, 55, 68-71, 82, 93, 104 Senaspis elliotii Austen, 1909: 90. Eristalis (Stenaspis) ellioti var. claricella Speiser, 1910: 123. Differential diagnosis. Species differentiated from all other Senaspis species by the conspicuous dense white to yellow pile on scutum, contrasting with the black pile on pleura (Fig. 3) (other species with dense pale pilosity on the scutum like S. melanthysana and S. umbrifera, have the pale pile continued on pleura (Figs 6, 9)). The wing is predominantly dark, except along posterior margin and at the apex where hyaline (Fig. 68).   ones. Frons black-brown; largely subshiny with weak greyish pollinosity along dorsal and lateral margins; dispersed short dark pile, dorsally somewhat longer, sometimes pile more pale. Face ground colour black-brown; covered with dense silvery pollinosity except facial tubercle which is bare; in parts with dispersed short pale pile; facial tubercle strongly pronounced. Gena colour and pollinosity as face; with short to long pale pile. Occiput blackbrown, covered with dull grey pollinosity; with dispersed pale pile except dorsally where sometimes darker yellow. Antennal segments black-brown to black, arista orange-brown.

Senaspis elliotii
Thorax (Figs 54,55). Scutum and scutellum completely covered by dense pale to orange-yellow pollinosity; furthermore with dense short pile of same colour, pile longer along margins. Scutellum marginated; weakly rounded, 2.5 times wider than long. Pleura ground colour black-brown, covered with dispersed long predominantly dark pile except on meron, dorsomedial anepimeron, ventral part of katepimeron, anterior part of katepisternum and anterior anepisternum. Legs. Black-brown, sometimes femora more red-brown; with short black pile, along posterior margin of pro-and mesofemora and ventral margin of metafemur with longer pile. Metaleg (Fig. 82), femur thickened, with slight ventral swelling in apical fifth, pile more dense where swollen; tibia thickened and curved, pile along ventral margin in apical half to two-thirds longer and more dense.
Wing (Fig. 68). Brownish throughout, sometimes with purplish shine when viewed from angle; alula hyaline and posterior margin narrowly and apex broadly paler; sometimes slightly paler maculae in centre of wing cells, paler areas not distinctly demarcated and sometimes absent; if present then usually in at least cells cup, dm, r 4+5 , and r 2+3 (Figs 69-71) (in type of var. claricella wing largely hyaline with slight fumose areas surrounding veins and cross-veins). Calypters dull chalk-white with fringe of silvery white pile; sometimes calypters and fringe more yellow. Cell r 1 open (Fig. 69) or closed, if closed usually not distinctly petiolate (Fig. 70), rarely with very short petiole less than one third of height of stigma (Fig. 71). In type of var. claricella narrowly open. Vein R 4+5 sinuate and usually distinctly short appendiculate, rarely without appendix. Abdomen (Fig. 93). Uniformly subshiny black to black-brown, postabdomen weakly brownish pollinose; with short dark pile except tergum 1 and postabdomen where pale pile. Sterna with long black pile. Male genitalia as in Fig. 104.
Female. As male except for the following character states: Eye dichoptic (Figs 22, 23), facets equal to subequal in size. Frons with brownish pollinose fascia in dorsal part for length equal to ocellar triangle, along dorsal and ventral margin of fascia narrowly greyish pollinose; frons usually with dispersed pale pile throughout, sometimes mixed with darker pile or completely black pile. Wing coloration variable, sometimes more uniformly brownish throughout but with more distinct hyaline maculae in several cells, rarely hyaline margins posteriorly broader. Cell r 1 rarely narrowly open.
Comments. The type of the variety claricella corresponds with the typical S. elliotii in all aspects except for the wing characteristics as described above. The narrowly open cell r 1 was observed in other material. No other specimens with the hyaline maculae were observed in the material examined, although the extension and distinctiveness of hyaline maculae in the wing cells was observed to be variable. We suspect that it concerns a teneral specimen of S. elliotii.
Several authors have spelled the name of this species in variant ways, i.e., as elliottii (e.g., Smith and Vockeroth 1980), ellioti (e.g., Speiser 1910) or elliotti (e.g., Curran 1927). In the original description Austen (1909) specifically stated that the species is named after Mr. G.H. Scott Elliot but indicated in the text that the specimens were collected by G.F. Scott Elliot (a Scottish botanist who collected in several African countries). In both cases the name was spelled as Elliot (with single 't') and Austen gave the species name as elliotii. This should be considered as the correct original spelling and alternative spellings should be considered as incorrect subsequent spellings according to article 33.4 of the ICZN. Macquart, 1850 Figs 4, 24-27, 56, 72, 83, 84, 94, 105 Senaspis flaviceps Macquart, 1850: 438. Protylocera apophysata Bezzi, 1915: 64. Syn. nov. Differential diagnosis. A large brown to reddish brown species (Fig. 4) differentiated from all other Senaspis species by conspicuous yellow face and frons (Fig. 24) (dark in all other species), and a bare katepimeron (pilose in all other species). The male metafemur bears a prominent basoventral tubercle (Fig. 83) (absent in all other species).
Legs. Brown to black-brown, femora partly more reddish brown ventrally; with short black pile, along posterior margin of pro-and mesofemora with longer pile. Metaleg (Fig. 83), femur distinctly thickened, with one distinct ventral tubercle in basal fourth to fifth, tubercle with distinct short dark pile; tibia thickened, distinctly bent at base, and only slightly curved, no longer pile along ventral margin.
Wing (Fig. 72). Yellowish brown tinge especially in anterior half, in parts more black-brown; towards posterior margin and apex more hyaline. Calypters black with fringe of silvery white pile. Cell r 1 closed, petiole at least as long as height of base of stigma. Vein R 4+5 sinuate but not appendiculate.
Abdomen (Fig. 94). Uniformly subshiny brown to reddish brown, terga IV and V and postabdomen often more rufous; with short dark pile, except tergum I where grey, and postabdomen where more rufous. Sterna dark; with long pale pile. Male genitalia as in Fig. 105.
Comments. The type material of S. flaviceps and S. apophysata was compared and considered to be conspecific. Senaspis apophysata is thus considered as a junior synonym of S. flaviceps. This synonymy was already suggested (Ssymank et al. in press, F.C. Thompson pers. comm.) but not formally published. The original description of S. flaviceps mentions the type locality as "De l'Afrique. Cap?" but the type specimen bears a label indicating "Madagascar" // "Goudot 1839". All studied material originates from Madagascar and no specimens collected on the African mainland were found. We, therefore, consider the current distribution of this species to be limited to Madagascar (and possibly Comoros; see Keiser 1971). Senaspis flaviceps differs from all other species within the genus in some aspects, such as the bare katepimeron (pilose in the rest, albeit weakly so), the presence of a basal tubercle in the male metafemur (absent in all others), the relatively longer petiole (at least as long as height of base of stigma, shorter in all others), and the larger body size (larger than 17 mm and up to 23 mm).

Differential diagnosis.
A species with a distinct medial dark brown macula on the wing (Fig. 73). It can be differentiated from other Senaspis species with a distinct wing macula by the coloration of the abdomen: largely brown with the posterior terga conspicuously orange to orange-red and with red pile (Fig. 95) (without red pile in S. dentipes (Fig. 91); red coloration and pile more extensive in S. xanthorrhoea (Fig. 100)).
Type ; same collection data as for preceding; 3 Jun. 1920 • 2♂♂; same collection data as for preceding; 1 Jan. 1921 • 1♀; same collection data as for preceding; 5 Jan. 1921 • 1♂; same collection data as for preceding; 7 Jan. 1921 • 1♀; same collection data as for preceding; 16 Jan. 1921 • 1♂; same collection data as for preceding; 14 Feb. 1921 • 1♂; same collection data as for preceding; 1 Jul. 1923 • 1♂; same collection data as for preceding; 2 May 1923 • 1♀; same collection data as for preceding ;Nov. 1929 • 1♀; same collection data as for preceding; Dec. 1939 • 1♀; same collection data as for pre- ceding; Dec. 1928;Ch. Seydel leg. • 1♀; (Fig. 5). Head (Figs 28, 29). Eye bare; holoptic, eye contiguity for distance equal to or slightly longer than length of ocellar triangle, facets dorsally slightly larger, at most twice as large in diameter, as ventral ones. Frons black to black-brown; weakly subshiny, with dense greyish pollinosity throughout; with dispersed medium long straw-yellow pile. Face black to black-brown; weakly subshiny, with dense greyish pollinosity, facial tubercle weakly shining black, posterolateral margin of mouth shining brownish; in parts with dispersed long pale pile; facial tubercle strongly pronounced. Gena colour and pollinosity as ventral lateral margin of face; with short to long pale pile. Occiput black-brown, covered with dully grey pollinosity; with dispersed pale pile, except dorsally where pile black adjacent to vertex. Antennal segments blackbrown, basoflagellomere apically more brownish, arista pale yellow.  Thorax (Fig. 57). Scutum mainly subshiny black; sparse grey pollinose, more of the wing (anterior margin basally more hyaline in S. griseifacies, infuscated in S. haemorrhoa) and the abdomen (terga II and III along posterior margin yellow in S. haemorrhoa, dark in S. griseifacies). Examination of long series of S. haemorrhoa and of type material of S. griseifacies has shown these characters to be variable. In addition, Bezzi (1912) contradicted the abdominal character partially in his detailed redescription where he indicated that in female specimens of S. griseifacies the "è spesso rosso anche l'orlo posterior del terzo segment" (partially red along posterior margin of the third segment). Both species are considered conspecific and thus S. griseifacies is considered junior synonym of S. haemorrhoa. Hervé-Bazin (1914) already alluded to this when indicating that S. griseifacies should be considered perhaps as a mere variety of S. haemorrhoa. An identification label 'Senaspis haemorrhoa' of 1996 by C. Kassebeer on one of the types of S. griseifacies at the KBIN collection also alludes to the synonymy but apparently was never formally published. (Speiser, 1913) Figs 6, 32-35, 58, 74, 86, 96, 108, 109 Protylocera melanthysana Speiser, 1913: 122. Differential diagnosis. A dark species (Fig. 6) without distinct macula on wing but with darker medial area (Fig. 74). It can be differentiated from S. nigrita by the basal half of the scutellum largely concolourous with the scutum (Fig. 58) (scutellum largely yellow, contrasting with dark scutum in S. nigrita; Fig. 59). It resembles strongly S. umbrifera but can be differentiated by the following characters: metafemur moderately thickened and straight to slight convex ventrally (Fig. 86) (thicker and concave in S. umbrifera; Fig. 88); abdomen with long dark pile along lateral margins (Fig. 96  preceding; KMMA • 1♂; same collection data as for preceding; Apr. 1915; AMNH • 1♂; same collection data as for preceding; CNC • 1♀; same collection data as for preceding; 2 Apr. 1915; AMNH • 1♂; same collection data as for preceding; 5 Apr. 1915 • 1♂ 1♀; same collection data as for preceding; 6 Apr. 1915 • 1♀; same collection data as for preceding; 7 Jul. 1915. Kenya • 1♀;Ngong;Apr. 1944;V.G.L. van Someren leg.;NHMUK. Uganda • 1♀;1-11 Sep. 1911; S.A. Neave leg.; NHMUK • 1♀; same collection data as for preceding ;12-20 Jan. 1912. Description. Body length: 12.6-19.0 mm. Wing length: 9.5-14.3 mm. Male (Fig. 6). Head (Figs 32,33). Eye bare; holoptic, eye contiguity for distance equal to length or 1.5 times length of ocellar triangle, facets dorsally slightly larger, at most twice as large in diameter as ventral ones. Frons black-brown; largely subshiny with black pollinosity in dorsal fifth only, along eye margins narrowly silver-grey pollinose; dispersed short dark pile, dorsally somewhat longer. Face black-brown; subshiny with pale brownish to greyish pollinosity, in parts more densely so, medial part and ventral lateral parts largely devoid of pollinosity; pollinose parts with dispersed long pale pile; facial tubercle strongly pronounced. Gena as pollinose parts of face; with short to long pale pile. Occiput black-brown, covered with dully grey pollinosity; with dispersed pale pile except dorsally where sometimes darker yellow to black. Antennal segments black-brown, arista orange-brown.
Legs. Mainly black to black-brown; with short black pile, along posterior margin of pro-and mesofemora and along ventral margin of metafemur with longer dark pile, sometimes base of pro-and mesofemora narrowly with more pale brownish pile; along ventral margin of metafemur with longer dark pile, basally with anterodorsal patch of longer dark pile. Metaleg (Fig. 86), femur moderately thickened, with ventral swelling in apical fifth; tibia slightly bent at base, thickened and curved, pile along ventral margin in apical half to two-thirds longer and more dense.
Wing (Fig. 74). Usually distinct fumose yellow-brown tinge, especially in medial part cell r 1 , basal part r 2+3 and distal part R; towards posterior margin and apex more greyish, sometimes posteriorly more hyaline. Calypters dark brown, concolourous with or darker than medial part wing; with fringe of black pile. Cell r 1 closed and petiolate, petiole at most as long as half the height of base of stigma. Vein R 4+5 sinuate; usually not appendiculate, rarely with short appendix. Abdomen (Fig. 96). Uniformly subshiny brown to black-brown; with short dark pile, except tergum I, and anterolateral parts of tergum II where pale; pilosity along lateral margins of all terga conspicuous and dense, along tergum IV and postabdomen longer. Postabdomen small. All sterna with dispersed long dark pile. Male genitalia as in Figs 108, 109.
Female. As male except for the following character states: Eye dichoptic (Figs 34,35), facets equal to subequal in size. Frons with black pollinose fascia in dorsal part for length at least equal to ocellar triangle, bordered by very narrow and less dense greyish-brown fascia. Abdomen, pilosity along lateral margins of all terga short and more dispersed.
Distribution. Cameroon, Democratic Republic of the Congo, Uganda. Also recorded from Kenya (De Meyer et al. 1995) but this needs to be confirmed as the material was unavailable for this study.
Comments. For similarities and differences with umbrifera, see comments under the latter. Both species occur sympatrically, like in the Democratic Republic of the Congo  (Bigot) 108, 109 S. melanthysana (Speiser) 110, 111 S. umbrifera (Walker) (holotype) 112, 113 S. nr umbrifera (Walker). tibia bent at base, thickened and slightly curved, pile along ventral margin in apical half to two-thirds longer and more dense.
Wing (Fig. 75). Faint yellowish tinge, near cross-veins r-m and bm-cu more yellow-brown but no distinct medial macula; distal part of cells r 2+3 and r 4+5 more hyaline, as well as along posterior margin, paler areas not distinctly demarcated; alula largely hyaline. Calypters dull straw yellow with fringe of silvery white pile. Cell r 1 closed, petiole very short, at most half height of base of stigma, rarely longer. Vein R 4+5 sinuate, appendix absent or present.
Abdomen (Fig. 97). Uniformly subshiny brown to black-brown, sometimes more rufous; with short dark pile except tergum I where more densely silver-grey pile; lateral margins intermixed with short pale pile, especially near postabdomen. Terga with dispersed long pale pile. Male genitalia as in Fig. 107.
Female. As male except for the following character states: Eye dichoptic (Figs 38, 39), facets subequal in size. Frons and face pollinosity predominantly greyish; frons with short dark pile dorsally, greyish pile ventrally; with narrow pale fascia dorsally of antennal implant. Thorax dark pile sometimes more extensively so. Leg pilosity sometimes more brownish.
Legs. Brown to black-brown, sometimes more reddish brown; with short black pile, along posterior margin of pro-and mesofemora with longer pile, sometimes more pale in basal part; along ventral margin of metafemur with longer dark pile, basally with anterodorsal patch of longer pale pile. Metaleg (Fig. 88), femur distinctly thickened and moderately curved, with one distinct ventral swelling in apical fifth, short black pile more dense where swollen; tibia slightly bent at base, thickened and curved, pile along ventral margin in apical half to two-thirds longer and more dense.
Wing (Figs 76,77). Faint yellowish brown tinge, more pronounced in medial part cell r 1 , basal part r 2+3 and distal part br; towards posterior margin and apex more greyish. Calypters yellow-white to pale brown, with fringe of yellow-white pile. Cell r 1 closed; if petiolate than petiole at most approx. as long as half the height of base of stigma. Vein R 4+5 sinuate but not appendiculate.
Abdomen (Figs 98,99). Uniformly subshiny red-brown to black-brown, anterolateral parts of tergum II sometimes less dark; sometimes indistinct black-brown pollinose medial macula along anterior margin of terga II and III; with short dark pile, except tergum 1, and anterolateral parts of tergum II where pale pile; lateral margins usually dark pilose, at most tergum IV partly pale pilose and terga II and III mixed pale and dark pile. Type of umbrifera lateral margins completely pale pilose (Fig. 98). Postabdomen conspicuously swollen. Sterna with dispersed long pale pile, on sterna IV and V darker. .
Female (based on material identified as near umbrifera). As male except for the following character states. Head (Figs 42,43), eye dichoptic, facets equal to subequal in size. Frons with black pollinose fascia in dorsal part for length at least equal to ocellar triangle, bordered by very narrow and less dense greyish-brown fascia. Scutellum, dark pile on disc less outspoken, more predominantly paly pilose. Wing, vein R 4+5 sometimes very short appendiculate. Abdomen with dark pile along lateral margins of all terga.
Distribution. Benin, Central African Republic, Democratic Republic of the Congo, Equatorial Guinea, Sierra Leone, Uganda (but see Comments).
Comments. The type specimen of S. umbrifera originates from Sierra Leone. It is in poor condition and the male genitalia were dissected prior to our study; thus, we cannot exclude a mixing of genitalia with another specimen. When comparing the genitalia with some non-type material, some slight differences were observed regarding the shape of the surstyli, the most explicit difference being the shape of the surstyli in lateral view (curved and pointed in the type species (Fig. 111); straight and not pointed in the other material (Fig. 113) and similar to the shape observed in S. melanthysana (Fig. 109). However, no major morphological differences could be observed and except for the differently shaped surstylus the type falls within the observed variability for the characters studied. The only other minor morphological difference observed is that the lateral margin of the abdominal terga of the type is covered with short pale pile while in all other specimens this is black or intermixed black and pale pile. Furthermore, the type is recognized by the entirely pale pile on the scutellum (variable in other specimens); the legs being more red-brown (brown to black-brown in others) and the calypters being yellow-white (yellow-white to pale brown in others). No additional specimens could be obtained from the same region while all non-type male specimens originate from Central Africa (Equatorial Guinea eastwards to Uganda). As the observed differences are very minor, we prefer to take a conservative position by provisionally listing all non-type material under S. umbrifera (listed as "Senaspis near umbrifera"). We consider the morphological differences too minor to warrant describing it as a separate species and propose to await additional material, especially from western Africa before making a formal decision. The only differentiating character (pale pile along lateral margins of abdomen) is, however, incorporated in the identification key. All major structures are also illustrated both for the type specimen and representative non-type specimens.
Senaspis umbrifera resembles S. melanthysana in most respect regarding body coloration and pilosity, and wing markings. However, a number of distinct differences could be discerned as pointed out in the key above: the lower calypter has a fringe of pale hairs (dark in melanthysana); the abdominal sterna I-III have long pale pile (dark in melanthysana), the lateral margins of the abdominal terga have short pale pile along most of their length (long dark pile in melanthysana), and the metafemur is strongly thickened and distinctly curved (moderately thickened and straight in melanthysana). (Bezzi, 1912) Figs 8, 48-51, 62, 78, 89, 100 Protylocera xanthorrhoea Bezzi, 1912: 416.

Differential diagnosis.
A species with a distinct medial dark brown macula on the wing (Fig. 78). It can be differentiated from other Senaspis species with a distinct wing macula by the coloration of the abdominal terga which is uniformly dark yellow to yellow-orange (Fig. 100) (at least terga I and II completely dark brown in S. dentipes (Fig. 91) and S. haemorrhoa (Fig. 95)).
Differential diagnosis. Different from all other Senaspis species by the head in lateral view without distinct protuding frons (Fig. 47); the unmarginated scutellum (Fig. 63), and the completely hyaline wing, with a distinctly open cell r 1 (Fig. 79). Description. Body length: 15.0 mm. Wing length: 12.2 mm. Female (Fig. 11). Head (Figs 46, 47). Eye bare; dichoptic, facets equal in size. Frons largely subshiny black-brown in ventral protruding part; dorsally with black pollinosity in front of ocellar triangle for length equal to ocellar triangle, between subshiny and black pollinose part with more dispersed greyish pollinosity continued ventrally narrowly along eye margin; dispersed short dark pile, except for area with greyish pollinosity where pile is pale. Face subshiny brown; with greyish pollinosity, medial part and ventral lateral margins largely devoid of pollinosity; in parts with dispersed long pale pile; facial tubercle weakly pronounced. Gena as pollinose part of face; with short to long pale pilosity. Occiput black-brown, covered with dully grey pollinosity; with dispersed pale pile except dorsally where black. Antennal segments black-brown, arista pale yellow. Thorax (Fig. 63). Scutum subshiny black, with brownish to brownish grey pollinosity; with short pale brown pile, along lateral margins intermixed with dispersed black pile, pilosity paler posteriorly, pilosity modereately long especially along margins. Scutellum rounded and not marginated, slightly more than twice as wide as long; pale brownish; with pale pilosity except anteriorly on disc where largely orange-brown pile (pile rubbed off in medial part); pilosity moderately long especially along apical margin; Pleura ground colour black-brown, covered with dispersed long pale pile except on meron, dorsomedial anepimeron, anterior part of katepisternum and anterior anepisternum (katepimeron obscured and absence or presence of pilosity not visible).
Legs. Brown to black-brown, pro-and mesofemora more orange-brown posteriorly, tarsal segments yellowish except major part of metabasotarsomere; with short black pilosity, along posterior margin of pro-and mesofemora with longer pale pile, tarsal segments, except major part of metabasotarsomere, with short pale pile; pro-and mesotibiae very dense. Metaleg (Fig. 90), femur moderately thickened, with ventral swelling in apical fifth; tibia thickened and curved, pile on ventral and dorsal margins along entire length, at least as long as width of tibia, and very dense.
Abdomen (Fig. 101). Subshiny brown to black-brown, weak brownish pollinose; tergum I more yellowish brown; tergum II anterior margin narrowly black, medial anterior half yellowish brown, laterally more extensively so, gradually darkening posteriorly; tergum III with pair of orange-brown fasciae in anterior two-fifths; with short pale pilosity, except tergum V and posterior margin of tergum IV where black pile.
Male. Unknown. Distribution. Democratic Republic of the Congo.
Comments. The position of this species within the genus Senaspis is uncertain. While there are some similarities with other Senaspis species (maculate eyes, wing venation except cell r 1 distinctly open, pilosity on metatibia), there are also some distinct differences. For instance, the shape of the head in lateral view (no strongly protruding frons, facial tubercle poorly developed, face extending more ventrally), the scutellum is unmargined, the completely hyaline wing, and the distinctly open cell r 1 . As the available material is limited to a single female specimen, we await additional material and/or further revision of other eristaline representatives from the Afrotropical region before proposing any generic assignment.

Discussion
The revised genus Senaspis now contains ten valid species, i.e., S. dentipes (Macquart), S. dibapha (Walker), S. elliotii Austen, S. flaviceps Macquart, S. haemorrhoa (Gerstaecker), S. nigrita (Bigot), S. pennata (Hervé-Bazin), S. melanthysana (Speiser), S. umbrifera (Walker), and S. xanthorrhoea (Bezzi). We herewith place the following species in synonymy: Senaspis apophysata (Bezzi) as junior synonym of S. flaviceps Macquart, S. livida (Bezzi) as junior synonym of S. dentipes (Macquart), S. nigripennis (Macquart) as junior synonym of S. dibapha (Walker), and S. griseifacies (Bezzi) as junior synonym of S. haemorrhoa (Gerstaecker). The generic characters, as given above in the generic diagnosis, are representative for all species. However, the closed and petiolate cell r 1 is a variable character with sometimes the petiole missing (see for example S. dentipes) or even slightly open (S. elliotii). The latter is also the case for S. pennata. This species shows a number of morphological differences (see comments listed under the species treatment) with the other species within the genus that makes its placement within this genus uncertain. Senaspis flaviceps also is slightly aberrant compared to the other Senaspis species: bare katepimeron (pilose in others), presence of a basoventral tubercle in the male metafemur (absent in all others), longer petiole (at least as long as height of base of stigma; shorter in all others) and the larger body size (more than 17 mm; shorter in all others). As S. flaviceps is the type species for the genus Senaspis, Thompson (pers. comm.) suggested that the generic concept of Senaspis should be restricted to S. flaviceps and all other taxa placed in a separate genus distinct from Senaspis. The available name Triatylosus (established as subgenus of Senaspis by Hull (1949) with Xylota dibaphus Walker as type species) has been proposed to be raised to genus rank and to include all Senaspis species except S. flaviceps. We, however, propose to wait for more taxonomic revisions for other Afrotropical eristaline groups to have a better understanding of their morphology and their phylogenetic relationships can be ascertained before making changes at generic level.
Besides the position of S. flaviceps, no distinct morphological clusters can be recognized among the remaining species although some taxa show morphological similarities. Some Senaspis species have a distinct wing marking with a well demarcated dark macula in the medial part (Figs 64,73,78). Within this group S. haemorrhoa and S. xanthorrhoea are similar in appearance with pale pilosity on face and frons (48)(49)(50)(51), partial to completely reddish pilosity and coloration of the abdomen (Figs 95,  100), and relatively broadened metafemur with ventrally two subapical swellings (Figs 85,89). Senaspis nigrita shares the latter characteristic with these two taxa (Fig. 87) while the wing marking is similar but with the medial wing marking less pronounced and demarcated (Fig. 75). Also, the male genitalia are similar with the surstyli, in dorsal view, bearing an inner row of stronger setae in the dorsal third (Figs 106, 107). The NJ and ML analysis (Fig. 114) tentatively suggest that S. haemorrhoa and S. nigrita are sister species (no genetic markers could be obtained for S. xanthorrhoea). Senaspis dentipes has identical wing markings to S. haemorrhoa and S. xanthorrhoea but is otherwise morphologically very distinct from both, including differences in male genital structures.
Senaspis melanthysana and S. umbrifera are also morphologically very similar to each other. Both species have a very similar appearance and a considerable number of specimens were misidentified in either way. Both have the wing markings more diffused with a general darkish tinge slightly more pronounced in the medial part (Figs 74,76,77). The general habitus is very dark, with the dorsal part of the thorax covered by a dense short and predominantly pale pile (Figs 6,9,10) continuing on the pleura. Morphological differences between both species are listed above in the taxonomic treatment of the taxa. Senaspis elliotii shows some similarities in general appearance ( Fig. 3) but is clearly distinct by the dense white to yellow pile on the dorsal part of the thorax, contrasting with the black pile on the pleura, and by the wing coloration which is predominantly dark, except along the posterior margin and at the apex (Fig. 68). Its relationship with the other taxa is unclear.
Senaspis dibapha does not show any morphological similarities with any of the other taxa within Senaspis. The general reddish appearance, morphological character states of additional facial tubercles laterally from the medial one (Figs 16, 18), and the slender metafemur (Fig. 81) are unique. The wing (Fig. 65) is largely darkened, except for the posterior margin, and somewhat similar to S. elliotii (Fig. 68).
All seven Senaspis species for which we obtained DNA barcodes are grouped as such in the NJ topology (Suppl. material 1: Fig. S1; Fig. 114) with a mean interspecific p-distance of 0.075 (range: 0.052-0.130), largely exceeding the mean intraspecific p-distance of 0.0037 (range: 0.002-0.005). The phylogenetic affinities among the species of this genus will be treated elsewhere (Mullens et al. unpublished).