Polyrhachis concava

Bolton (1973) - Apart from the fact that the species is arboreal, nothing is known of its habits. Wheeler (1922a:265) records that the species has been found in the stomachs of toads and pangolins.

Identification
A member of the Polyrhachis militaris species-group. Bolton (1973) - The distinctive form of the eye immediately separates this species from all others of the militaris group in the Ethiopian region. A similar eye structure is known from some species of the Indo-Malayan region and in the subgenus Hemioptica.

Distribution based on Regional Taxon Lists
Afrotropical Region: Cameroun, Central African Republic, Congo, Democratic Republic of Congo, Equatorial Guinea, Gabon, Ghana, Ivory Coast, Sierra Leone.

Nomenclature

 *  concava. Polyrhachis concava André, 1889: 218 (w.) SIERRA LEONE. André, 1892a: 45 (q.). Combination in P. (Myrma): Forel, 1916: 448. See also: Bolton, 1973b: 299.

Worker
Bolton (1973) - TL 6.8-7.6, HL 1.85-1.92, HW 1.29-1.37, CI 69-74, SL 2.29-2.40, SI 172-180, PW 1.00-1.18, MTL 2.37-2.55. (28 measured.)

Anterior margin of clypeus arcuate and entire. Sides of head in front of eyes shallowly but distinctly concave, slightly narrower than immediately behind the eyes. Sides of head behind the eyes rounding into the extremely convex occipital margin. Eyes in full face view appearing convex but in profile or postero-dorsal view it can be seen that the side of the head bordering the ventral margin of the eye is raised and extended to form a blinder, which appears to obscure the ventral margin of the eye, giving it a reniform outline. Dorsum of alitrunk transversely concave, the propodeum much more strongly so than the pronotum. Alitrunk marginate throughout its length, interrupted only at the sutures. The marginations of the constituent segments projecting and flange-like, more strongly so on the propodeum than on the pronotum. Pronotum armed with a pair of spines, propodeum with a pair of upcurved teeth of variable length, usually quite small but occasionally long and spine-like. Promesonotal suture distinct; metanotal groove impressed. Petiole with a pair of very long dorsal spines, divergent and curving backwards over the gaster in profile, and with a pair of short upcurved spines laterally, of variable length. Anterior face of first gastral segment vertical, not concave in the middle of the face.

Erect hairs present only on anterior clypeal margin and apex of gaster. Pubescence yellowish to pale golden in colour, densest on the alitrunk where it hides the sculpturation, less dense on the head and gaster.

Sculpturation everywhere of a fine superficial reticulation, finer on clypeus than on remainder of head.

Queen
Bolton (1973) - As worker but on the alitrunk only the propodeum is concave between the two small, obtuse teeth found in this caste. Propodeum strongly marginate.

Type Material
Bolton (1973) - Holotype worker, SIERRA LEONE.

References based on Global Ant Biodiversity Informatics

 * André E. 1892. Matériaux myrmécologiques. Rev. Entomol. (Caen) 11: 45-56.
 * Bernard F. 1953. La réserve naturelle intégrale du Mt Nimba. XI. Hyménoptères Formicidae. Mémoires de l'Institut Français d'Afrique Noire 19: 165-270.
 * Bolton B. 1973. The ant genus Polyrhachis F. Smith in the Ethiopian region (Hymenoptera: Formicidae). Bulletin of the British Museum (Natural History). Entomology 28: 283-369.
 * Braet Y., and B. Taylor. 2008. Mission entomologique au Parc National de Pongara (Gabon). Bilan des Formicidae (Hymenoptera) recoltes. Bulletin S. R. B. E./K.B.V.E. 144: 157-169.
 * Fisher B. L. 2004. Diversity patterns of ants (Hymenoptera: Formicidae) along an elevational gradient on Monts Doudou in southwestern Gabon. Memoirs of the California Academy of Sciences 28: 269-286.
 * 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.
 * Taylor B., N. Agoinon, A. Sinzogan, A. Adandonon, Y. N'Da Kouagou, S. Bello, R. Wargui, F. Anato, I. Ouagoussounon, H. Houngbo, S. Tchibozo, R. Todjhounde, and J. F. Vayssieres. 2018. Records of ants (Hymenoptera: Formicidae) from the Republic of Benin, with particular reference to the mango farm ecosystem. Journal of Insect Biodiversity 8(1): 006–029.
 * Wheeler W. M. 1922. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. II. The ants collected by the American Museum Congo Expedition. Bulletin of the American Museum of Natural History 45: 39-269.
 * Wheeler W. M. 1922. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. VIII. A synonymic list of the ants of the Ethiopian region. Bulletin of the American Museum of Natural History 45: 711-1004