Ocymyrmex zekhem

A Namibian series collected by Alan Marsh at Samanab River (Skeleton Coast), Swakopmund, and two workers from Hunkab Springs, belong to this species, which was previously known only from the holotype.

Identification
Bolton and Marsh (1989) - O. zekhem is closely related to Ocymyrmex velox but differs in being generally darker in colour, having long standing hairs on the first gastral tergite which equal the length of the erect hairs on the propodeum, and by having longer scapes (SI > 110) than are seen in velox (SI < 110). The samples of zekhem now available indicate that the intensity of cephalic sculpture is slightly variable, as specimens with more conspicuous dorsal cephalic costulae than others are fairly frequent. The occipital region varies from very feebly striolate to virtually smooth. Colour in zekhem varies from having the head very dark dull red to reddish or brownish black. The alitrunk is always glossy jet black. The gaster is blackish brown but the petiole and postpetiole may have a reddish tint. Currently the known range of dimensions in zekhem are TL 8.0-9.5, HL 2.06-2.20, HW 1.90-2.04, CI 91-93, SL 2.20-2.28, SI 111-116, PW 1.22-1.40, AL 2.50-2.70 (10 measured).

Key to Ocymyrmex workers

Distribution based on Regional Taxon Lists
Afrotropical Region: Namibia, South Africa.

Nomenclature

 *  zekhem. Ocymyrmex zekhem Bolton, 1981b: 281 (w.) NAMIBIA. Bolton & Marsh, 1989: 1278 (q.). See also: Bolton & Marsh, 1989: 1306.

Worker
Holotype. TL 8.4, HL 2.06, HW 1.90, CI 92, SL 2.20, SI 116, PW 1.40, AL 2.50.

Anterior clypeal margin entire, without trace of a median notch or impression. Maximum diameter of eye 0.40, about 0.21 x HW, the eyes only just failing to break the outline of the sides in full-face view. Sides of head in front of eyes straight, diverging anteriorly; behind the eyes the sides rounding broadly and evenly into the occipital margin, the latter very shallowly impressed medially in full-face view. Antennal scapes the longest yet known in the genus (see SI, above). With the alitrunk in profile the promesonotum low, evenly shallowly convex. Posterior part of mesonotum and anterior part of propodeum sloping gently downwards posteriorly, the posterior half of the propodeal dorsum levelling off for a short distance before rounding smoothly into the gently convex declivity. Metapleural lobes low and narrow, rounded and only slightly projecting, but not at all concealed by the metapleural gland bulla in absolute profile. Petiole in profile with ventral surface of peduncle shallowly sinuous but without a developed process. Dorsal surface of peduncle also irregular and passing through a blunt angle about one-third the way from the base. Petiole node evenly rounded and dome-like in profile; long and narrow in dorsal view, longer than broad and no broader than the posterior peduncle, the sides of the node scarcely convex. Postpetiole in dorsal view broader than long. Base of first gastral tergite no wider than the postpetiole in dorsal view but not forming a narrow neck; instead the sides of the tergite diverge quickly and evenly from the base. Dorsum of head with sculpture almost effaced, the surface between the eyes with faint narrow longitudinal costulae which are quite close-packed and almost effaced in places. Occipitally the costulae present are even weaker than between the eyes and are transverse. Ground-sculpture between the narrow costulae everywhere vestigial or absent, the surface shining and mostly smooth. Dorsum of pronotum transversely arched-rugose, centrally with an area of longitudinal rugosity; everywhere else the alitrunk transversely rugose. Sides of alitrunk more strongly sculptured than dorsum, the rugae no denser but more sharply defined and more strongly developed. Petiole, postpetiole and gaster unsculptured except for a faint superficial reticular pattern. All dorsal surfaces of head and body with numerous standing hairs. Basal half of first gastral tergite with a number of conspicuous long hairs which are as long as those on the dorsal alitrunk. Head very dark dull red, alitrunk glossy jet black, remainder of body blackish brown but the pedicel segments with a reddish tint. Legs and antennae dark dull red to reddish dark brown, approximately the same colour as the sides of the head.

Type Material
Holotype worker, South West Africa: Tsisab Cyn., Brandberg Mts, 550 m, 11.v.1958 (E. S. Ross & R. E. Leech).