Polyrhachis medusa

An individual was hand collected in primary forest. Little else is known of this species' biology.

Identification
A member of the Polyrhachis militaris species-group. Bolton (1973) - Closely related to Polyrhachis schistacea, from which it may be separated by the extremely dense clothing of long hairs and the density of the pubescence, which conceals the fine superficially reticulate sculpturation. Casual observation may possibly confuse this species with more densely hairy individuals of Polyrhachis militaris, but the characters quoted under couplet 45 of the key to species will serve to discriminate the two.

Distribution based on Regional Taxon Lists
Afrotropical Region: Kenya, Mozambique, United Republic of Tanzania.

Biology
Bolton (1973) - Alate females have been recorded from Tanzania in May and September. Due to its large size and affinities one would expect it to be a ground nesting species as Polyrhachis schistacea. Santschi (1914a:140) noted there is a large Clubionid spider, “probably Apochinomma formicaeforme Pavesi”, which mimics medusa.

Nomenclature

 *  medusa. Polyrhachis schistacea r. medusa Forel, 1897c: 206 (w.q.m.) TANZANIA. Combination in P. (Myrma): Santschi, 1914b: 140. Subspecies of schistacea: Forel, 1901h: 78; Wheeler, W.M. 1922a: 1002. Raised to species: Forel, 1907g: 92; Santschi, 1914b: 140; Emery, 1925b: 199. See also: Bolton, 1973b: 312.

Worker
Bolton (1973) - TL 12.6-14.4, HL 2.74-3.00, HW 2.40-2.52, CI 84-88, SL 3.37-3.56, SI 139-142, PW 2.24-2.52, MTL 3.51-3.70. (13 measured.)

Anterior clypeal margin straight to shallowly and broadly concave. Eye shape ranging from weakly concave to weakly convex but usually more or less flat. Sides of head and occipital margin convex; the eyes when flat not breaking the outline of the sides of the head in full-face view. Alitrunk marginate throughout its length, the marginations interrupted at the promesonotal suture and the impressed metanotal groove. Pronotal spines long, narrow and weakly incurved; propodeal armament reduced to a pair of blunt tubercles. The margination of the mesonotum and propodeum is often irregular, giving a chipped and jagged appearance in dorsal view. Dorsal surfaces of alitrunk transverseiy convex. Petiole with a pair of spines at the dorsolateral angles and a pair of laterally placed strong, acute teeth.

Head, body and appendages densely clothed with long, erect white hairs, some of which are curved or sinuate. Pubescence everywhere long and dense, white or off-white in colour and completely hiding the sculpturation.

Sculpturation everywhere of a very fine, superficial reticulation (revealed by scraping off the pubescence). Colour black, but specimens have a greyish appearance due to the very dense pubescence.

Queen
Bolton (1973) - As worker, with the usual differences associated with this caste. Propodeum not marginate, the dorsum rounding into the sides.

Type Material
Bolton (1973) - Syntype workers, queen, male, TANZANIA: Zanzibar (A. Voeltzkow).

References based on Global Ant Biodiversity Informatics

 * 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.
 * Forel A. 1897. Ameisen aus Nossi-Bé, Majunga, Juan de Nova (Madagaskar), den Aldabra-Inseln und Sansibar, gesammelt von Herrn Dr. A. Voeltzkow aus Berlin. Mit einem Anhang über die von Herrn Privatdocenten Dr. A. Brauer in Marburg auf den Seychellen und von Herrn Perrot auf Ste. Marie (Madagaskar) gesammelten Ameisen. Abhandlungen der Senckenbergischen Naturforschenden Gesellschaft 21: 185-208.
 * Forel A. 1907. Ameisen von Madagaskar, den Comoren und Ostafrika. Wissenschaftliche Ergebnisse. Reise in Ostafrika 2: 75-92.
 * Garcia F.H., Wiesel E. and Fischer G. 2013.The Ants of Kenya (Hymenoptera: Formicidae)Faunal Overview, First Species Checklist, Bibliography, Accounts for All Genera, and Discussion on Taxonomy and Zoogeography. Journal of East African Natural History, 101(2): 127-222
 * IZIKO South Africa Museum Collection
 * Robson Simon Database Polyrhachis -05 Sept 2014
 * 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