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(Figs 18, 22, 23)
Worker. TL 7.4 - 7.8, HL 1.70 - 1.90, HW 1.64 - 1.82, CI 96 - 100, SL 1.48 - 1.60, SI 86 - 96, PW 1.08 - 1.20, AL 2.20 - 2.30 (20 measured).
Anterior clypeal margin with a conspicuous median semicircular impression which is flanked on each side by a low tooth or denticle, this tooth usually quite low and rounded, uncommonly strongly prominent. Maximum diameter of eye 0.34 - 0.40, about 0.20 - 0.22 x HW. Shape of alitrunk as in Fig. 18, the promesonotum evenly and broadly convex, sloping posteriorly to the propodeal dorsum; the latter rounding evenly into the declivity. Metapleural lobes small and low, bluntly rounded or broadly and bluntly truncated, sometimes reduced to a narrow little-projecting strip. Petiole node in profile small, low and smoothly rounded. In dorsal view the petiole node varying from slightly longer than broad to slightly broader than long. Postpetiole as broad as long to slightly broader than long in dorsal view. First gastral tergite constricted and forming a neck basally. Dorsum of head sculptured with low, rounded, feeble longitudinal costulae which may be very reduced or even effaced in places. Spaces between the costulae without ground-sculpture, the surface smooth and polished, with a slick and glossy appearance. Sides of alitrunk closely and finely sharply constulate, the dorsum sharply transversely costulate except between the mesothoracic spiracles where the sculpture is usually longitudinal. Pronotal dorsum in front of the longitudinal sculpture finely arched-costulate to smooth, the sculpture always weaker than elsewhere on the alitrunk, sometime partially or wholly effaced or the costulae reduced to vestiges. This weakening of the sculptural intensity may also affect the longitudinal costulae between the mesothoracic spiracles. Ventral surface of petiole node with a few transverse rugulae which may be very feeble but which normally extend for some distance up the sides of the node before fading out. Dorsum of petiole node unsculptured or at most with vestiges remaining. Dorsum of peduncle usually with transverse fine rugulae but these may be very reduced and faint. Postpetiole unsculptured or at most with some fine superficial patterning. All dorsal surfaces of head and alitrunk with numerous hairs of varying length, the first gastral tergite with hairs shorter and sparser than elsewhere. Colour glossy dull red, the gaster darker, blackish brown to black; entire body with a polished and shining appearance.
Only nitidulusHNS and celerHNS, among the species with the clypeus impressed and gaster constricted basally, lack strong ground-sculpture between the costulae or rugulae of the dorsal head. This gives them a slick and very polished appearance which immediately separates them from their allies in which granular or punctulate ground-sculpture is present, and which in consequence are dull and less polished. O. nitidulusHNS and celerHNS are separated by the shape of the pronotum, which is flat in the latter, rounded in the former (compare Figs 18 and 19), and by the shape of the head which is longer and narrower in celerHNS than in nitidulusHNS.
Ethiopia: Meisso (K. Guichard). Kenya: Kajiado (G. Nyamasyo), Kajiado (J. Darlington). Uganda: N. Turkana Prov. (Lake Rudolf expd.). Tanzania: Longido West (A. Loveridge).
Found most commonly in these habitats: 2 times found in acacia woodland, 1 times found in Combretum/Acacia woods.
Found most commonly in these microhabitats: 2 times on the ground, 2 times Foraging.
Collected most commonly using these methods: 5 times Hand, 2 times search.
Elevations: collected from 605 - 1804 meters, 1224 meters average