Eumerus obliquus (Fabricius, 1805)

Ricarte, Antonio, Hauser, Martin, Kinnee, Scott & Marcos-García, Ángeles, 2020, A new Eumerus hoverfly (Diptera: Syrphidae) from Namibia and South Africa with notes on similar species, Zootaxa 4890 (4), pp. 493-508 : 503

Key to the African species of the Eumerus obliquus group

The Eumerus obliquus group as defined in the discussion includes E. incilis Smit in Smit et al. (2017) , E. lyneborgi sp. nov., E. obliquus , E. unicolor Loew, 1858 [= E. wainwrighti ( Curran, 1938) ] and E. vestitus .

1. Face below antennae polished black, without pollinosity; scutum shiny, without a pattern of pollinose markings or only with a faint vestigial pattern; tarsomeres 4 and 5 of all legs black, contrasting conspicuously with the reddish brown tarsomeres 1‾3; male eyes separated by a distance equalling the width of the anterior ocellus.............................. E. unicolor

- Face below antennae always pollinose; scutum with a conspicuous pattern of pollinose markings, more reduced but still conspicuous in E. incilis [see figure 39 and 40 in Smit et al. (2017)]; tarsi of all legs either uniform in colour or with a dark gradient towards the apex; male eyes holoptic...................................................................... 2

2. Metatarsomere 2 with a conspicuous apical extension ( Fig. 3A, B ); male metabasotarsomere unmodified.................................................................................................... E. lyneborgi sp. nov.

- Metatarsomere 2 without apical extensions; male metabasotarsomere strongly modified in most species, simple in E. punctifrons ............................................................................................... 3

3 Metatibia with 2‾3 short black apical spinae ( Fig. 11A ); posterior half of tergum IV extensively pollinose............... 4

- Metatibia without apical spinae ( Fig. 11B ); tergum IV shiny between the two diagonal pollinose vittae and the posterior margin of tergum............................................................................................ 5

4 Eye with short sparse pile; metabasotarsomere brown ( Fig. 9B ) and, in male, with a small basal tooth in the sulcus [see figure 30 in Smit et al. (2017)]......................................................................... E. vestitus

- Eye usually bare; metabasotarsomere black and, in male, without teeth in the dorsal sulcus [see figure 27 in Smit et al. (2017)]....................................................................................... E. incilis

5 Vertex with black pile and extensive areas free of pollinosity or sparsely pollinose [see figure 4A in Garcete-Barrett et al. (2020)]; male metabasotarsomere laterally compressed, with a dorsal ridge [see figure 4E in Garcete-Barrett et al. (2020)].............................................................................................. E. obliquus

- Vertex without black pile, covered in dense pollinosity except for a narrow area surrounding each ocellus [see figure 57 in Smit et al. (2017)]; male metabasotarsomere without ridge.............................................. E. punctifrons

Figures

FIGURE 3. Eumerus lyneborgi sp. nov., metatarsus. A: male, holotype, scale bar = 0.25mm; B: female, paratype (Namibia), scale bar = 0.5 mm. Legend: e, spur-like expansion.

FIGURE 9. Eumerus vestitus, male, lectotype, body, overall appearance. A: dorsal view with original labels; B: lateral view. Scale bar = 1 mm.

FIGURE 11. Eumerus vestitus, females, paralectotypes, metatibiae.A: specimen with typical E. vestitus morphology; B: outlier specimen (non-conspecific?). Scale bar = 0.25 mm.