Ocymyrmex tachys

Identification
The character combination of small size, very reduced palp formula (PF 2,3), medially impressed clypeus, eyes which strongly break the outline of the sides of the head, and unconstricted gaster, renders the tachys-group immediately recognizable. (Bolton and Marsh 1989)

Distribution based on Regional Taxon Lists
Afrotropical Region: Namibia.

Nomenclature

 *  tachys. Ocymyrmex tachys Bolton & Marsh, 1989: 1304 (w.) NAMIBIA.

Worker
Holotype. TL 5.2, HL 1.36, HW 1.22, CI 90, SL 1.30, SI 107, PW 0.76, AL 1.60.

Palp formula 2,3; one of only two Ocymyrmex species so far known to have just 2 maxillary palp segments, the other being Ocymyrmex engytachys. Anterior clypeal margin with a conspicuous median impression. With the head in full-face view the eyes very obviously breaking the outline of the sides. Eyes relatively large, the maximum diameter 0.32, about 0.26 x HW. Sides of head in front of eyes straight and weakly divergent anteriorly. Behind the eyes the sides convergent posteriorly and rounding into the transverse occipital margin; the latter not indented nor concave medially. Alitrunk in profile with pro meso no tum evenly convex, the mesonotum sloping posteriorly and confluent with the propodeum, which slopes slightly less steeply backwards. Propodeal dorsum and declivity confluent through a long shallow curve which is only weakly convex and appears almost like a continuation of the dorsum. Bulla of meta pleural gland strongly prominent posteriorly, almost masking the metapleural lobe, the apex of which can just be seen posteriorly. Petiole node in profile evenly rounded, in dorsal view slightly longer than broad. Postpetiole about as long as broad in dorsal view, broadest posteriorly. Postpetiolar sternite ventrally evenly shallowly transversely concave, lacking a strong median longitudinal groove. In profile outline of first gastral tergite shallowly convex basally from its articulation with the postpetiole; first sternite with a more or less flat outline in its basal third. In dorsal view the gaster not strongly constricted nor neck-like basally. Gaster no wider than postpetiole at their point of junction but behind this the sides of the tergite are evenly and distinctively divergent. Dorsum of head finely irregularly longitudinally rugulose, the rugulae faint and feebly divergent posteriorly. Spaces between rugulae with conspicuous granular to punctulate ground-sculpture, which tends to become very weak or to fade out occipitally. Dorsal alitrunk densely and finely regularly transversely rugose except on the pronotum where the sculpture is strongly arched and finer than elsewhere. Sides of alitrunk regularly rugose; longitudinal on pronotum, oblique elsewhere. Petiole mostly finely reticulate but the ventral surface with some transverse rugulae below the node, and the dorsum with some faint to vestigial transverse rugulae on the node. Postpetiole superficially reticulate. First gastral tergite mostly glassy smooth but basally with the faintest traces of fine superficial reticular patterning. All dorsal surfaces of head and body with conspicuous silvery standing hairs, those on the basal half ofthe first gastral tergite about equal in length to those on the propodeal dorsum. Head dark reddish brown, mandibles and head to level of frontal lobes lighter brown. Alitrunk black, gaster intermediate in shade between head and alitrunk.

Paratypes. TL 5.2-5.7, HL 1.36-1.42, HW 1.22-1.31, CI 88-92, SL 1.30-1.40, SI 107-108, PW 0.76-0.84, AL 1.60-1.70 (4 measured).

As holotype but maximum diameter of eye 0.24-0.26 x HW. One paratype is a teneral and light brown in colour. In the remainder the colour of the alitrunk varies from dark brown to black.

Type Material
Holotype worker, Nambia (=South West Africa): Namib Desert, Skeleton Coast, sample SC6, Il.viii.1982, 19 deg. 45 min. S., 13 deg. 23 min. E., gravel outcrop (A.C. Marsh). Paratypes, 4 workers with same data as holotype (BMNH, ).