Polyrhachis otleti

Bolton (1973) - In the original description Forel records that the nest was in a cleft in the bark of a tree, 8 cm long and 2.5 cm broad, covered by a linen thread mixed with vegetable matter. A nest found by the present author in Nigeria was approximately 5 ft above ground level in a narrow, deep rot hole in a tree being used as shade in a cocoa plot. The entrance was covered by a fibrous mat composed of silk mixed with small pieces of bark which extended for quite some distance around the entrance hole of the nest proper. A number of workers were resting on the bark of the tree under this mat and when the cover was broken ran out to investigate. Some specimens from Ghana collected by Dr D. J. Cross bear the label, “In carton patch nest, on tree”, which obviously refers to the same sort of structure.

Identification
Rigato (2016) - A hairy, moderately large revoili-group species with marginate pronotum and propodeal dorsum delimited posteriorly by a pair of well developed ridges.

Two workers from CASC collection are very similar to the types, but have a shining gaster (subopaque in types), due to more superficial sculpturation and much sparser gastral pubescence. The distance between adjacent pubescence elements is much larger than their length; while in types gastral pubescence is much denser (the distance between adjacent hairlets is shorter than their length). Because of the paucity of available material and variability of these features in other Polyrhachis, I consider all of them as conspecific.

Distribution based on Regional Taxon Lists
Afrotropical Region: Central African Republic, Democratic Republic of Congo, Ghana, Nigeria, United Republic of Tanzania.

Nomenclature

 *  otleti. Polyrhachis (Myrma) otleti Forel, 1916: 449 (w.q.m.) DEMOCRATIC REPUBLIC OF CONGO. See also: Bolton, 1973b: 336.

Worker
Bolton (1973) - TL 6.8-7.6, HL 1.63-1.71, HW 1.33-1.37, CI 80-83, SL 1.88-2.00, SI 140-146, PW 1.13-1.23, MTL 1.89-1.96, (9 measured.)

Anterior clypeal margin projecting medially as a truncate lobe, the angles of which are acute. Middle of the margin of this lobe with a small notch. Eyes convex, sides of head in front of eyes weakly convex, convergent; behind the eyes rounding into the broadly convex occipital margin. Dorsum of alitrunk transversely convex. Pronotum armed with a pair of triangular spines and marginate throughout its length, Mesonotum more obtusely marginate, the marginations distinct only when viewed from certain angles. Propodeum not marginate. Promesonotal suture present as a weakly incised, arcuate line; the metanotal groove usually very indistinct, represented only by a faint scoring across the dorsum of the alitrunk. Propodeum armed posteriorly with a pair of transverse ridges which appear as small teeth in profile. The ridges fail to meet medially and there is a small but distinct gap through which the dorsum meets the declivity. Petiole with a pair of long dorsal spines and a pair of shorter, lateral spines. The anterior surface of the first gastral segment concave medially.

Entire body, including head, with numerous long, white hairs and a fairly abundant long pubescence.

Clypeus, propodeal declivity, petiole and gaster finely reticulate. Head finely rugose, longitudinally so on the vertex but more distinctly reticulate-rugose in the space separating the eye from the frontal carina on each side. Alitrunk dorsally very finely longitudinally rugose, the direction most distinct on the pronotum. Colour black, dull, the apices of the antennal funiculi and the tarsi brown or red-brown.

Rigato (2016) - (n=6) 4 syntype workers + 2 workers from CAS). HL 1.40–1.68, HW 1.19–1.39, CI 81–86, SL 1.68–1.98, SI 140–146, FW 0.47–0.51, FI 36–39, PW 1.07–1.29, WL 1.84–2.25, HTL 1.67–2.00.

Queen
Bolton (1973) - As worker apart from the usual differences associated with caste, the pronotal spines reduced.

Type Material
Bolton (1973) - Syntype workers, queen, male, CONGO (Kinasha): St Gabriel (H. Kohl) [examined].

References based on Global Ant Biodiversity Informatics

 * Medler J. T. 1980: Insects of Nigeria - Check list and bibliography. Mem. Amer. Ent. Inst. 30: i-vii, 1-919.
 * Rigato F. 2016. The ant genus Polyrhachis F. Smith in sub-Saharan Africa, with descriptions of ten new species. (Hymenoptera: Formicidae). Zootaxa 4088: 1-50.
 * Robson Simon Database Polyrhachis -05 Sept 2014
 * Taylor B. 1978. Ants of the Nigerian Forest Zone (Hymenoptera: Formicidae). II. Formicinae, Dolichoderinae. Cocoa Research Institute of Nigeria Research Bulletin 5: 1-57.