Pristomyrmex orbiceps (Santschi) (Fig. 37)

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 : 286-287

Pristomyrmex orbiceps (Santschi) (Fig. 37)

Xiphomyrmex orbiceps Santschi , 1914 b: 367, fig. 30. Syntype workers, Cameroun: Victoria (Silvestri); and

Ghana: Aburi (Silvestri) (NM, Basle) [examined]. Pristomyrmex orbiceps (Santschi) Santschi, 1916: 51. Hylidris laevigatus Weber, 1952: 20, fig. 12. Holotype worker, Zaire: 13 miles [21 km] S. of Asa, lat. 4 40 ' N, long. 25 40 ' E., 3. iii. 1948, no. 2170.1 (N. A. Weber) (AMNH, New York) [examined]. Syn. n.

Worker. TL 2.9 - 3.4, HL 0.72 - 0.90, HW 0.75 - 0.94, CI 100 - 106, SL 0.62 - 0.74, SI 80 - 87, PW 0.48 - 0.62, AL 0.72 - 0.88 (25 measured).

Base of mandible usually with 1 - 2 rugulae present but these fading out distally so that the blade near the apical margin is almost or entirely smooth. Apical (masticatory) margin with strong apical and preapical tooth followed by a diastema and a broad basal tooth formed by the fusion of two basal denticles. In many specimens this broad basal tooth shows two points but with wear only a single blunt prominence remains. Clypeus frequently with a weak median longitudinal carina but this tends to be reduced, present only posteriorly, or entirely absent. Anterior clypeal margin equipped with small denticles, usually 5 in number, consisting of a median and 2 on each side. Degree of development of the denticles is variable, ranging from a bluntly crenulate appearance to very distinct. Frontal carinae present, running back at least to the level of the posterior margins of the eyes and strongly divergent in their anterior halves. Strongly developed scrobes absent but the sides between the frontal carinae and the eyes sloping outwards and flat to very shallowly concave. Maximum diameter of eye 0.14 - 0.19, about 0.18 - 0.21 x HW and usually with 7 - 9 ommatidia in the longest row, though in smaller individuals only 6 may be present. With the head in full-face view the occipital margin shallow concave to quite conspicuously indented medially, the sides convex. With the alitrunk in profile the pronotum armed with a low broad blunt tubercle, without the conspicuous acute teeth or spines seen in other species; in dorsal view these tubercles appearing as low bluntly rounded angles. Propodeum armed with a pair of spines which are usually longer than their basal width but which are variable in length and, at minimum, may be only as long as their basal width. Metapleural lobes prominent and rounded. Petiole and postpetiole in profile rounded, without acute angles. Dorsum of head between frontal carinae to occipital margin smooth and highly polished. Sides of head mostly smooth but with some scattered foveolate punctures in front of, below, and behind the eyes. These punctures are generally fairly conspicuous but in some individuals they may be faint or even vestigial, especially behind the eyes. In most specimens, but especially in larger ones, a few punctures occur on the side of the head on a line linking the posterior margins of the eyes with the posterior extension of the frontal carinae, but these are frequently vestigial or absent. Alitrunk, petiole, postpetiole and gaster unsculptured. Hairs very sparse, present on mouthparts, ventral surface of head and gastral apex, but otherwise as follows. Dorsum of head behind level of antennal insertions with 2 - 3 pairs of hairs along the line of the frontal carinae. Occipital corners with one pair of hairs, Dorsal alitrunk without hairs except for a single pair on the mesonotum, and this pair is frequently lost by abrasion. Petiole, postpetiole and first gastral tergite without hairs. Scapes and tibiae lacking hairs but with fairly conspicuous pubescence which is usually more obvious on the former than on the latter. Colour uniform blackish brown to black, the appendages lighter.

P. orbiceps is a widely distributed species, occurring throughout the wet forest zones of West and Central Africa. Nests are constructed in fallen twigs or larger pieces of wood in the leaf litter layer and workers forage singly in the litter. The separation of orbiceps from other African species is straightforward. It differs from cribrarius as that species is heavily sculptured and densely hairy. P. trogor lacks frontal carinae, has long scapes and relatively small eyes. The widely distributed africanus differs from orbiceps as follows:

orbiceps

Pronotum with a pair of blunt tubercles.

Maximum eye diameter 0.18 - 0.21 x HW.

Eye with usually 7 - 9 ommatidia in the longest row (sometimes with 6). Dorsum of head behind antennal insertions with 2 - 3 pairs of hairs. Dorsal alitrunk with 1 pair of hairs. Head between frontal carinae smooth.

Scapes relatively somewhat shorter, SI range 80 - 87.

africanus

Pronotum with a pair of acute teeth or short spines. Maximum eye diameter 0.12 - 0.15 x HW. Eye with only 4 - 5 ommatidia in longest row.

Dorsum of head behind antennal insertions with more than 5 pairs of hairs.

Dorsal alitrunk with 4 or more pairs of hairs.

Head between frontal carinae with foveolate punctures, at least posteriorly.

Scapes relatively somewhat longer, SI range 85 - 94.

Material examined

Ivory Coast: Divo (L. Brader); Banco For. nr Abidjan (W. L. Brown); Orstom Exp. Sta. (W. L. Brown). Ghana: Kibi (D. Leston); Bunso (D. Leston); Mampong (D. Leston); Mampong (P. Room); Tafo (B. Bolton); Mt Atewa {B. Bolton). Nigeria: Gambari (B. Bolton); Gambari (B. Taylor). Cameroun: Nkoemvon (D. Jackson). Gabon: Plateau d'I passa (J. A. Barra); Makokou (W. H. Gotwald). Angola: Dundo (no name).