Polyrhachis medusa

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Polyrhachis medusa
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Camponotini
Genus: Polyrhachis
Subgenus: Myrma
Species group: militaris
Species: P. medusa
Binomial name
Polyrhachis medusa
Forel, 1897

Polyrhachis medusa casent0217782 p 1 high.jpg

Polyrhachis medusa casent0217782 d 1 high.jpg

Specimen Labels

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


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.

Keys including this Species


Distribution based on Regional Taxon Lists

Afrotropical Region: Kenya, Mozambique, United Republic of Tanzania.

Distribution based on AntMaps


Distribution based on AntWeb specimens

Check data from AntWeb


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.



The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • 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.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.



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.


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) (Musee d'Histoire Naturelle Genève).


  • Bolton, B. 1973b. The ant genus Polyrhachis F. Smith in the Ethiopian region (Hymenoptera: Formicidae). Bulletin of the British Museum (Natural History) Entomology. 28:283-369. PDF (page 312, see also)
  • Emery, C. 1925d. Hymenoptera. Fam. Formicidae. Subfam. Formicinae. Genera Insectorum 183: 1-302 (page 199, Raised to species)
  • Forel, A. 1897d. 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 un (page 206, worker, queen, male described)
  • Forel, A. 1901m. Formiciden des Naturhistorischen Museums zu Hamburg. Neue Calyptomyrmex-, Dacryon-, Podomyrma- und Echinopla-Arten. Mitt. Naturhist. Mus. Hambg. 18: 43-82 (page 78, Subspecies/race of schistacea)
  • Forel, A. 1907g. The Percy Sladen Trust Expedition to the Indian Ocean in 1905, under the leadership of Mr. J. Stanley Gardiner, M.A. VI. Fourmis des Seychelles, Amirantes, Farquhar et Chagos. Trans. Linn. Soc. Lond. Zool. (2) 12: 91-94 (page 92, Raised to species)
  • Santschi, F. 1914b. Voyage de Ch. Alluaud et R. Jeannel en Afrique Orientale, 1911-1912. Résultats scientifiques. Insectes Hyménoptères. II. Formicidae. Paris: Libr. A. Schulz, pp. 41-148. (page 140, Combination in P. (Myrma), Raised to species)
  • Wheeler, W. M. 1922j. 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. Bull. Am. Mus. Nat. Hist. 45: 711-1004 (page 1002, Subspecies/race of schistacea)