Species of the argentatus group

The argentatus group contains the following nine species: Sphex erythrinus, S. feijeni nom. nov., S. fumicatus, S. lanatus, S. rufinervis, S. taschenbergi, S. tomentosus, S. torridus and S. voeltzkowii.

This group was proposed by Hensen (1991), when it primarily encompassed species from the Australis and Orientalis regions. He correctly assigned the Afrotropical S. fumicatus to the group, and Schmid-Egger (2014) added S. taschenbergi based on Palearctic records. The species treated here conform to Hensen’s diagnostic character, a bituberculate metanotum (Fig. 7). In most species of the group, the tubercles are usually very distinct, but occasional specimens and particularly members of S. erythrinus, S. feijeni nom. nov. and S. rufinervis have them more indistinct. Therefore, we opted to rely on an additional character for species group assignment that was mentioned by Bohart & Menke (1976): the presence of a linear swelling in front of the upper part of the spiracular groove (Fig. 9). Only members of the argentatus group possess both of these traits, whereas others may have an indistinctly bituberculate metanotum but lack the spiracular swelling (Fig. 10). In the satanas group, the swelling is present, but the metanotum is always unmistakably flat.

Males in the argentatus group seem to have much greater intraspecific size variations than those of other groups. Length differences of up to ± 20% were observed. When sequenced, the differences in the CO1 gene for a small and a large individual of S. lanatus were minimal, so any size variations may simply be the result of differing amounts of available food during larval development.

In contrast to all other African species groups of Sphex, the orientation of the erect propodeal setae is not uniform within this group.