Polyrhachis militaris

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Polyrhachis militaris
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. militaris
Binomial name
Polyrhachis militaris
(Fabricius, 1782)

Polyrhachis militaris casent0094091 profile 1.jpg

Polyrhachis militaris casent0094091 dorsal 1.jpg

Specimen Label

Synonyms

One of the largest and most common members of the genus in forested Africa. Polyrhachis militaris nests arboreally, typically in a rotten part of a living tree.

Identification

Rigato (2016) - A large member of the militaris group with a somewhat rectangular head, hairy body and appendages, and long, usually at least partially golden pubescence, which hides most of the body sculpture.

The head of Polyrhachis militaris (and Polyrhachis doudou as well, see above) is subrectangular and clearly different from the rounded outline of similar species, i.e. Polyrhachis epinotalis, Polyrhachis gagates, Polyrhachis medusa and Polyrhachis schistacea. These species have a more or less elongate, oval or suboval head, mostly with a widely convex posterior margin and usually (except most epinotalis) the head is slightly wider behind than in front of the eyes. Moreover, militaris and doudou have a blunt margination behind each eye delimiting head dorsum from the sides.

Bolton (1973) - One of the largest and most variable species of the genus found in forested Africa. Intergrades exist between all the described forms of pubescence colouration and distribution, and slight variations in pubescence are often to be found in the same nest series. One interesting point is that forms in which the pubescence is golden everywhere appear to be restricted to northern East Africa, and a long series from the Tero Forest, Uganda, are notable for their very bright golden pubescence. In West Africa the golden colour is usually paler or has a coppery or bronze tint.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Angola, Cameroun, Central African Republic, Congo, Democratic Republic of Congo, Equatorial Guinea, Gabon, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Kenya, Liberia, Malawi, Mozambique, Nigeria, Sierra Leone, Sudan, Togo, Uganda, United Republic of Tanzania, Zambia.

Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Bolton (1973) - The species is arboreal and nests are made in rotten parts of standing trees, often a considerable distance above the ground. Nests are usually constructed in the trunk or the stub of a broken branch, or in branches which have previously been mined by termites. As far as is known, silk is not utilised in nest building. If the colony is disturbed the workers curve their gasters beneath the alitrunk and eject quantities of formic acid. At the same time they tap their gasters on the floor of the nest, giving a distinct rattling sound when performed by a number of workers. Foraging is undertaken singly and the ants cross the forest floor from tree to tree. If disturbed whilst on a branch or a tree trunk the workers release their grip and fall to the ground. Workers of militaris are mimicked in West Africa by nymphs of a coreid bug, probably belonging to the genus Mirperus Stal.

Alate females have been recorded as follows, Ghana: June, September, October. Nigeria: May. Uganda: January, July, September, October. Kenya: November. Tanzania: February, June. Congo (Kinshasa) : January, February, March, April, September, November.

Fungi

This species is a host for the fungus Ophiocordyceps unilaterialis (Shrestha et al., 2017).

Castes

Worker

Nomenclature

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

  • militaris. Formica militaris Fabricius, 1782: 493 (q.) "Tropical Africa". Smith, F. 1858b: 72 (m.); Mayr, 1866b: 886 (w.). Combination in Myrma: Billberg, 1820: 104; in Polyrhachis: Smith, F. 1858b: 72; in P. (Myrma): Santschi, 1914b: 140. Senior synonym of bruta, calabarica, cupreopubescens, ssibangensis, striativentris: Bolton, 1973b: 313; of epinotalis, nkomoensis: Dorow, 1995: 36, 37 respectively. Material of the unavailable names argentatus, dido, pleurata, sankisiana, transversaria referred here by Bolton, 1973b: 313.
  • cupreopubescens. Polyrhachis militaris r. cupreopubescens Forel, 1879a: 120 (q.) "AFRICA". Forel, 1907a: 38 (w.); Wheeler, G.C. & Wheeler, J. 1953e: 207 (l.). Combination in P. (Myrma): Santschi, 1914b: 140. Raised to species: Dalla Torre, 1893: 261. Subspecies of militaris: Mayr, 1895: 154; Wheeler, W.M. 1922a: 998. Junior synonym of militaris: Bolton, 1973b: 313.
  • striativentris. Polyrhachis militaris r. striativentris Emery, 1892d: 566 (w.) IVORY COAST. Santschi, 1912b: 166 (q.). Combination in P. (Myrma): Wheeler, W.M. 1922a: 999. Subspecies of militaris: Emery, 1896d: 777; Wheeler, W.M. 1922a: 999. Junior synonym of militaris: Bolton, 1973b: 313.
  • calabarica. Polyrhachis militaris var. calabarica Forel, 1907a: 38 (w.) NIGERIA. Junior synonym of militaris: Bolton, 1973b: 313.
  • ssibangensis. Polyrhachis militaris var. ssibangensis Forel, 1907a: 38 (w.) GABON. Santschi, 1910c: 400 (q.). Combination in P. (Myrma): Wheeler, W.M. 1922a: 998. Junior synonym of militaris: Bolton, 1973b: 313.
  • bruta. Polyrhachis militaris st. bruta Santschi, 1912b: 166 (q.) DEMOCRATIC REPUBLIC OF CONGO. Santschi, 1924b: 223 (w.). Combination in P. (Myrma): Wheeler, W.M. 1922a: 998. Junior synonym of militaris: Bolton, 1973b: 313.
  • nkomoensis. Polyrhachis militaris var. nkomoensis Santschi, 1924b: 222 (w.) DEMOCRATIC REPUBLIC OF CONGO (in key). [First available use of Polyrhachis (Myrma) militaris r. cupreopubescens var. nkomoensis Forel, 1916: 447 (w.q.m.); unavailable name (Bolton, 1973b: 313).] Junior synonym of militaris: Dorow, 1995: 37.

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

Description

Worker

Bolton (1973) - TL 10.8-14.1, HL 2.59-3.41, HW 1.96-2.96, CI 75-86, SL 3.18-3.89, SI 132-162, PW 1.74-2.34, MTL 3.51-4.45. (30 measured.)

Anterior clypeal margin truncate medially. Eyes weakly to strongly convex, the sides of the head in front of the eyes convex. Behind the eyes the sides may round immediately into the occipital margin, may be convergent posteriorly or may be more or less parallel, rounding into the occipital margin posteriorly. In some specimens the dorsum of the head behind the eyes is separated from the sides by a blunt angle. Alitrunk strongly marginate throughout its length, interrupted at the sutures. On each segment the margination projects laterally or vertically as a rim or flange; usually this is best developed on the pronotum where the margination is continued anteriorly on to the spines as a raised dorsal ridge. Pronotum armed with a pair of long, acute spines; propodeum with a pair of upcurved teeth or spines of very variable length. Promesonotal suture distinct; metanotal groove impressed. Petiole armed dorsally with a pair of long spines, and laterally with a pair of teeth. Anterior face of first gastral segment vertical or very shallowly concave.

Erect hairs abundant on all surfaces, greyish, .silvery, golden or yellow-brown in colour. Pubescence everywhere dense, long, variable in colour and in arrangements of colour. The pubescence usually golden or grey to silver-grey, often with both colours occurring on the same specimen. The most common colour forms of the pubescence are as follows.

1. Entirely golden.

2. Golden, with sides of alitrunk grey or silver-grey.

3. Dorsum of alitrunk golden, the rest grey or silver-grey.

4. Dorsum of gaster golden, the rest grey or silver-grey.

Pubescence densest on the dorsum of the alitrunk and gaster, often completely masking the underlying sculpturation, especially on the former.

Sculpturation of head and alitrunk of a fine, longitudinal striate-rugulation, visible on the head and usually also visible on the outer edges of the pronotal dorsum at the bases of the spines. Removal of the propodeal pubescence shows that the sculpturation on this segment, although usually longitudinal, may be transverse or even diagonal. Gaster usually finely and densely reticulate-punctate, but occasionally striate-rugose, either longitudinally or transversely, or in some cases, whorled.

Rigato (2016) - HL 2.37–3.24, HW 1.76–2.51, CI 70–80, SL 3.08–3.92, SI 152–176, FW 0.63–0.82, FI 31–37, PW 1.52–2.32, WL 3.37–4.45, HTL 3.40–4.60. (n=32)

Queen

Bolton (1973) - As worker but with finer sculpturation, reduced pronotal spines, petiolar spines and propodeal teeth. The margination of the propodeum is reduced and that of the pronotum indistinct.

Type Material

Holotype queen, Tropical Africa, (BMNH).

References

  • Billberg, G. J. 1820. Enumeratio insectorum in Museo Gust. Joh. Billberg. Stockholm: Gadel, 138 pp. (page 104, Combination in Myrma)
  • 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 313, Senior synonym of bruta, calabarica, cupreopubescens, ssibangensis and striativentris, Material of the unavailable names argentatus, dido, pleurata, sankisiana and transversaria referred )
  • Dorow, W. H. O. 1995. Revision of the ant genus Polyrhachis Smith, 1857 (Hymenoptera: Formicidae: Formicinae) on subgenus level with keys, checklist of species and bibliography. Cour. Forschungsinst. Senckenb. 185: 1-113 (page 36, 37, Senior synonym of epinotalis and nkomoensis)
  • Fabricius, J. C. 1782 [1781]. Species insectorum exhibentes eorum differentias specificas, synonyma, auctorum loca natalia, metamorphosin adiectis observationibus, descriptionibus. Tome I. Hamburgi et Kilonii [= Hamburg and Kiel]: C. E. Bohn, 552 pp. (page 493, queen described)
  • Mayr, G. 1866b. Diagnosen neuer und wenig gekannter Formiciden. Verh. K-K. Zool.-Bot. Ges. Wien 16: 885-908 (page 886, worker described)
  • 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.
  • 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))
  • Shrestha B, Tanaka E, Hyun MW, Han JG, Kim CS, Jo JW, Han SK, Oh J, Sung JM, Sung GH. 2017. Mycosphere Essay 19. Cordyceps species parasitizing hymenopteran and hemipteran insects. Mycosphere 8(9): 1424–1442 (DOI 10.5943/mycosphere/8/9/8).
  • Smith, F. 1858a. Catalogue of hymenopterous insects in the collection of the British Museum. Part VI. Formicidae. London: British Museum, 216 pp. (page 72, male described, Combination in Polyrhachis)