Polyrhachis equina

Identification
Polyrhachis equina and Polyrhachis gribodoi are very similar and share numerous characters including almost identical, bilobed anterior clypeal margins, distinctly concave mesonotal and propodeal dorsa, dorso posteriorly extended propodeal spines and similarly shaped petioles. They differ in their relative size (HL <1.80 in P. equina versus HL >1.90 in P. gribodoi) and in several other characters, including the shape of the head and the sculpturation of the mesosomal dorsum. In P. equina, the sides of the head in front of the eyes converge towards the mandibular bases in an almost straight line, while behind the eyes the sides round into a moderately convex occipital margin. In P. gribodoi the sides of the head in front of the eyes are distinctly convex, and behind the eyes the sides round into a virtually flat occipital margin. The mesosomal dosum of P. equina is finely, rather irregularly, reticulate-punctate, with the reticulae on the pronotum somewhat bowed towards its lateral margins. The sculpturation of the mesosomal dorsum in P. gribodoi is distinctly more intense and more regularly, longitudinally striate on pronotum. (Kohout 1988)

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Indonesia, Malaysia.

Nomenclature

 *  equina. Polyrhachis equinus Smith, F. 1857a: 63 (w.) BORNEO. Combination in P. (Campomyrma): Wheeler, W.M. 1919e: 122. Senior synonym of biloba: Wheeler, W.M. 1919e: 122. See also: Kohout, 2007c: 10.
 * biloba. Polyrhachis biloba Forel, 1911a: 58 (w.) BORNEO. Junior synonym of equina: Wheeler, W.M. 1919e: 122.

Polyrhachis equinus

Holotype worker in. Labelled “SAR. 21” (= Sarawak) and with a Donisthorpe type-label.

Worker
Kohout (1988) - Dimensions (holotype cited first): TL c. 6.40, 6.05- 6.65; HL 1.72, 1.56-1.80; HW 1.43, 1.25-1.50; CI 83, 79-83; SL (missing), 2.03-2.18; SI (missing), 159- 164; PW 0.87, 0.75-0.90; MTL 2.09, 2.00-2.25 (12 measured).

References based on Global Ant Biodiversity Informatics

 * Chapman, J. W., and Capco, S. R. 1951. Check list of the ants (Hymenoptera: Formicidae) of Asia. Monogr. Inst. Sci. Technol. Manila 1: 1-327
 * Emery C. 1886. Saggio di un catalogo sistematico dei generi Camponotus, Polyrhachis e affini. Memorie della Reale Accademia delle Scienze dell'Istituto di Bologna 5: 363-382
 * Fayle T. M., D. P. Edwards, E. C. Turner, A. J. Dumbrell, P. Eggleton, and W. A. Foster. 2012. Public goods, public services and by-product mutualism in an antfern symbiosis. Oikos 121(8): 1279-1286.
 * Forel A. 1911. Fourmis de Bornéo, Singapore, Ceylan, etc. récoltées par MM. Haviland, Green, Winkler, Will, Hose, Roepke et Waldo. Rev. Suisse Zool. 19: 23-62.
 * Kohout R.J. 2007. A review of the subgenus Polyrhachis (Campomyrma) Wheeler from Borneo with descriptions of new species. Asian Myrmecology 1: 7-17.
 * Pfeiffer M.; Mezger, D.; Hosoishi, S.; Bakhtiar, E. Y.; Kohout, R. J. 2011. The Formicidae of Borneo (Insecta: Hymenoptera): a preliminary species list. Asian Myrmecology 4:9-58
 * Robson Simon Ant Collection, 05-Sept-2014
 * Robson Simon Database Polyrhachis -05 Sept 2014
 * Smith, F. "Catalogue of the hymenopterous insects collected at Sarawak, Borneo; Mount Ophir, Malacca; and at Singapore, by A. R. Wallace." Journal of the Proceedings of the Linnean Society of London, Zoology 2 (1857): 42-88.
 * Wheeler W. M. 1919. The ants of Borneo. Bulletin of the Museum of Comparative Zoology 63:43-147.
 * Widodo E.S., M. Mohamed, and Y. Hashimoto. 2001. Canopy ant diversity assessment in the fragmented rainforest of Sabah, East Malaysia. Nature and Human activities 6: 13-23.
 * Woodcock P., D. P. Edwards, T. M. Fayle, R. J. Newton, C. Vun Khen, S. H. Bottrell, and K. C. Hamer. 2011. The conservation value of South East Asia's highly degraded forests: evidence from leaf-litter ants. Phil. Trans. R. Soc. B. 366: 3256-3264.
 * Yamane S.; Nona, A. R. 1994. Ants from Lambir Hills National Park, Sarawak. Pp. 222-226 in: Inoue, T.; Hamid, A. A. (eds.) 1994. Plant reproductive systems and animal seasonal dynamics. Long-term study of dipterocarp forests in Sarawak. Kyoto: Center for Ecological Research, Kyoto University, vii + 255 pp.
 * Yusah K. M., T. M. Fayle, G. Harris, and W. A. Foster. 2012. Optimizing diversity assesment protocols for high canopy ants in tropical rain forest. Biotropica 44(1): 73-81.