Ocymyrmex robecchii Emery

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 : 276

Ocymyrmex robecchii Emery

(Fig. 24)

Ocymyrmex robecchii Emery , 1892: 114, fig. Syntype workers, Somali Republic: Uebi (Robecchi), and Erdal (Pavesi) (MHN, Geneva; MCSN, Genoa) [examined].

Worker. TL 9.2 - 9.3, HL 2.20 - 2.22, HW 202 - 204, CI 92, SL 208 - 216, SI 103 - 106, PW 1.26 - 1.28, AL 2.52 - 2.60 (2 measured).

Anterior clypeal margin with a strong semicircular median impression flanked by a pair of short rounded denticles. Outline shape of head as in Fig. 24, the head longer than broad (CI <100), with sides which converge posteriorly, and with the occipital margin strongly impressed medially. Maximum diameter of eye 0.40, about 0.20 x HW. Scapes long, SI> 100. With alitrunk in profile the mesonotum anteriorly forming a distinct hump behind the pronotum, the two not forming a single continuous convexity. Orifices of meso-thoracic spiracles protected by a pair of low tumuli or welts which project from the surface. Mesonotal dorsum sloping shallowly downwards posteriorly and confluent with the propodeal dorsum which is flat to very feebly concave to the level of the spiracle where it becomes shallowly convex and rounds broadly and evenly into the declivity. Metapleural lobes large and strongly developed, prominent, broadly subtriangular in shape and slightly upcurved. Peduncle of petiole without a ventral process. Petiole node in dorsal view very narrow, slightly expanded. Postpetiole in dorsal view much longer than broad. Basal portion of first gastral tergite constricted, forming a narrow neck behind the postpetiole. Dorsum of head with arched-longitudinal costulae on the genae and frontal lobes, the costulae curving in towards the midline posteriorly. Remainder of dorsum to occipital margin densely transversely costulate. Ground-sculpture vestigial, merely a superficial patterning between the costulae. Sides of alitrunk strongly, regularly and sharply costulate everywhere, the dorsum similarly sculptured, as is the propodeal declivity. All dorsal sculpture transverse except between the mesothoracic spiracles. Petiole encircled by fine rugulae or costulae which are most strongly developed ventrally. Postpetiole and gaster unsculptured. All dorsal surfaces of head and body with scattered acute hairs of varying length; those on the first gastral tergite shorter and sparser than elsewhere. Colour dark dull red, the postpetiole and gaster lighter, yellowish.

A large and conspicuous species, robecchii is characterized by its strongly impressed median clypeal notch, transverse cephalic sculpture, strongly impressed occipital margin, long scapes and large size. Although the two specimens seen possess the transverse cephalic sculpture characteristic of females in this genus, they lack the associated characters of shorter thicker scapes and broader, more parallel-sided frontal lobes which are usually associated with this caste (see discussion under the generic diagnosis). For this reason I have chosen to treat these specimens as bona fide workers for the time being, and have used the direction of cephalic sculpture as a key character in case they do not turn out to be females. This of course cannot be ascertained until more material becomes available.