Key A: Species of the Sphex argentatus group

1. Erect propodeal setae brown or black............................................................................................2

– Erect propodeal setae silvery or golden..........................................................................................5

2. Cellular wing area with yellow or ferruginous tinge; wing base not notably infuscate (Figs 58– 59). Madagascar and surrounding islands only..............................................................................3

– Cellular wing area without yellow tinge; wing base markedly fuscous (Figs 49, 52). Widespread..........................................................................................................................................................4

3. Female: apical margin of fore- and hindwing completely fuscous (Fig. 58). Male: erect clypeal and paraocular setae uniformly black ......................................................... S. torridus F. Smith, 1873

– Female: apical margin of forewing only anteriorly with fuscous spot, apex of hindwing hyaline. Male: erect clypeal setae silvery intermixed with black ones; erect paraocular setae uniformly silvery-golden ............................................................................................. S. voeltzkowii Kohl, 1909

4. Erect clypeal setae entirely or largely silvery (Fig. 53) ....................... S. fumicatus Christ, 1791

– Erect clypeal setae black (Fig. 54) ................................................ S. taschenbergi Magretti, 1884

5. Appressed and erect setae on face and propodeum rich golden, sometimes silvery. Hindfemur and most of hindtibia brightly ferruginous (Fig. 57) ............................... S. tomentosus Fabricius, 1787

– Erect setae on face silvery or silvery-golden, sometimes intermixed with black ones; erect setae on propodeum silvery (Figs 41–44, 50–51). Hindleg darker............................................................6

6. Erect clypeal setae at least partially black. Seychelles .............................. S. rufinervis Pérez, 1895

– Erect clypeal setae uniformly silvery...............................................................................................7

7. Female: wings with yellow tinge (Fig. 41); petiole length less than 1.7 × its medial width. Male: very broad placoids (nearly width of segment) covering flagellomeres III–VI .............................. .............................................................................................................. S. erythrinus (Guiglia, 1939)

– Female: wings without yellow tinge (Figs 43, 50); petiole length more than 1.7× its medial width. Male: placoid(s) more narrow (at most half as wide as segment), covering flagellomeres III–V or only V.................................................................................................................................................8

8. Female: lower part of clypeus brightly ferruginous; propodeal enclosure not obscured by vestiture, with 7–10 distinct transversal ridges (Fig. 43). Male: setae laterally on gonostyles hyaline (Fig. 46); mid- and hindlegs completely black; placoids covering entire length of flagellomeres III–V ......... .............................................................................................................................. S. feijeni nom. nov.

– Female: clypeus black; propodeal enclosure without any distinct ridges, posterior half obscured by appressed setae (Fig. 50). Male: gonostyles laterally with stout black setae (compare Fig. 45); mid- and hindlegs partially ferruginous; single placoid on proximal half of flagellomere V .......... .................................................................................................................... S. lanatus Mocsáry, 1883