Ocymyrmex zekhem, Bolton, B., 1981

Bolton, B., 1981, A revision of six minor genera of Myrmicinae (Hymenoptera: Formicidae) in the Ethiopian zoogeographical region., Bulletin of the British Museum (Natural History) Entomology 43, pp. 245-307 : 281

Ocymyrmex zekhem sp. n.

Holotype worker. 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.

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

O. zekhem is one of the seven species known in this genus which lack a notch or impression in the anterior clypeal margin. Of these seven species two, laticeps and cursor , have the base of the first gastral tergite constricted and forming a narrow neck, which quickly separates them from zekhem . Two other species, turneri and cavatodorsatus , are differentiated from zekhem by being much smaller and having shorter scapes, as well as by their possession of specializations not seen in zekhem . In turneri the eyes are large (028 x HW) and very conspicuously break the outline of the sides of the head in full-face view; in cavatodorsatus the alitrunk outline is strongly saddle-shaped. The only other known species which lack a clypeal notch are ankhu and velox , a close species-pair. In both these species, however, the scapes are shorter than in zekhem and the first gastral tergite lacks conspicuous long hairs on the basal half. Such pilosity is distinct in zekhem where the hairs are as long as those on the dorsal alitrunk, whereas in both ankhu and velox hairs are frequently absent from the first tergite, and when present they are very sparse, short and inconspicuous.