Plesianthidium (Spinanthidium) richtersveldense Eardley & Griswold, sp. nov.

(Figs 21–23)

Diagnosis. The female of P. richtersveldense is distinguished by the combination of completely black integument and pubescence, and absence of a longitudinal carina on S6. Males can be recognized by the entirely black integument, mostly black pubescence, the absence of a ventral spine on the hind trochanter. In addition the structure of S7 (Fig. 23 c) and S8 (Fig. 23 d) are diagnostic.

Within the subgenus Spinanthidium, the size and colour of P. richtersveldense is unique. In the colour of integument and pubescence it superficially resembles P (C.). cariniventre, but lacks the carinate female S6 and the tuberculate male hind trochanter.

Description. Female. Lengths: face 3.9–4.2 mm; scutum 3.3–3.5 mm; forewing 10.0– 10.2 mm; body 10.8– 12.0 mm. Integument completely black (Fig. 22 a). Pubescence black (Fig. 22 a); metasomal terga without distal fasciae; scopa partly black. Preoccipital ridge rounded; distance between lateral ocellus and preoccipital ridge twice ocellar diameter; supraclypeus distinctly convex; clypeus distinctly convex, not modified ventrally, ventral edge crenulate, densely punctate; mandible with three teeth; maxillary palpus 2-segmented; scutum very densely punctate; tegula densely punctate medially; propodeum glabrous medioventrally; T2–T3 without distal fasciae, sparsely punctate distally; T6 slightly expanded posterolaterally, without mediolongitudinal carina.

Male. Lengths: face 4.0– 4.3 mm; scutum 3.4–3.5 mm; forewing 11.0– 11.2 mm; body 14.5–15.0 mm. Integument black. Pubescence black, except face, anterior and lateral scutum and anterior mesepisternum partly white (Figs 22 c, d); metasomal terga without distal fasciae. Preoccipital ridge rounded; distance between lateral ocellus and preoccipital ridge twice ocellar diameter; paraocular area black; supraclypeus distinctly convex; clypeus, distinctly convex, densely punctate; mandible black, with three distinct teeth; maxillary palpus 2- segmented; scutum very densely punctate medially; tegula densely punctate; propodeum glabrous medioventrally; hind trochanter without ventral spine; T2–T5 without distal fasciae; T6 with very small mediolongitudinal carina, with small tubercle posteromedially, with small lateral spines; T6 with distal margin punctate, without distal flange; T7 posterior edge tridentate with large lateral and median teeth, all spines narrow and blunt (Fig. 23 a); S4 without apicomedian comb; S5 broadly and deeply emarginate posteromedially; S6 broadly and unevenly convex (Fig. 23 b); S7 disc short, narrowly and deeply concave posteriorly, with small point posteromedially (Fig. 23 c); S8 with disc long, strongly concave posterolaterally, emarginate posteromedially, expanded laterally subapically (Fig. 23 d); gonostylus concave apicolaterally (Fig. 23 e).

Etymology. This species is named for the type locality, the Richtersveld, which is a mountane desert.

Associated organism. Monechma molissimum .

Distribution (Fig. 21). Although first identified from material collected in the Richtersveld, P. richtersveldense is also found in southern Namibia.

Type material (eight specimens). Holotype, female. Namibia. NW of Aus, 26.37S 16.11E, 2005. ix.18, F.W. Gess, on Berkheya spinosissima (1♀ AMGC 15090). South Africa. Koeroegabvlakte, Richtersveld National Park, 28.11S 17.03E, 1995. ix.17–24, 1996. ix.14, F.W. Gess, on Monechma molissimum (3♀ 2♂ paratypes AMGC 53193, 53197, 53196, 53200, 53202); Hell’s Kloof road, Richtersveld National Park, 28.18.89S 16.15.264E, 12.x.2008, C. Eardley (1♀ paratype SANC 19232); Kliphoogte, 29.0656S 17.4019E, 2011. ix.14, L. Packer (1♀ paratype PC 15277 A9); De Koei, Richtersveld N. P., 28.2817S 16.9932, 2007. ix.9, T. Griswold (1♂ BLCU 722593). Holotype deposited in AMGC; paratypes in AMGC, SANC, PC, BLCU.