Polyrhachis

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Polyrhachis
Polyrhachis bihamata
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Camponotini
Genus: Polyrhachis
Smith, F., 1857
Type species
Formica bihamata, now Polyrhachis bihamata
Subgenera
Diversity
782 species
1 fossil species
(Species Checklist)

Polyrhachis bihamata casent0010659 profile 1.jpg

Polyrhachis bihamata

Polyrhachis bihamata casent0010659 dorsal 1.jpg

Specimen Label

Synonyms
Evolutionary Relationships


Gigantiops
  (1 species)



Santschiella
  (1 species)





Myrmoteras
  (41 species)


Camponotini

Colobopsis
  (116 species)




Opisthopsis
  (20 species)




Dinomyrmex
  (2 species)




Polyrhachis
  (782 species)




Camponotus
  (1,488 species)




Calomyrmex
  (14 species)



Echinopla
  (36 species)









Based on Ward et al. 2016.
Rudy Kohout has spent more than 2 decades revising members of this diverse genus. His ongoing publications focus on sets of species placed in species groups. These groups are organized by subgenera. Dorrow (1995) presented the first contemporary reorganization of what had previously slowly developed into a messy tangle of poorly organized groups and forms. Kohout's revisions have altered some of Dorrow's groupings. This has come about as particular species and groups have been more carefully assessed. There no longer exists any published overview detailing how all the species groups are organized under their respective subgenera. Antwiki does present some of these updated group revisions and species keys (species groups are presented on their respective subgenera for many groups; see the subgenera listed in the taxobox on the right side of this page). A phylogenetic analyses, using molecular sampling, has recently examined the relationships within and between existing groups (Mezger & Moreau 2015, see below). Not all of the groupings are supported by this analysis. Most of the modern taxonomic revisions have been clear in stating that the current groupings are logical constructs largely based on similarities in morphology and are not phylogenetic hypotheses. Both the species groups and subgenera are important considering the current taxonomic state of the genus as a whole.

Photo Gallery

  • Polyrhachis Shattuck 52538 Danum Valley Sabah-web.jpg
  • Polyrhachis Shattuck 52551 Danum Valley Sabah-web.jpg
  • Polyrhachis Shattuck 52650 Danum Valley Sabah-web.jpg
  • Polyrhachis Shattuck 52661 Danum Valley Sabah-web.jpg
  • Shattuck N2-5660-web, Polyrhachis rufifemur, near Bungendore, NSW.jpg
  • Polyrhachis Shattuck 52949 Danum Valley Sabah-web.jpg
  • Polyrhachis Shattuck 53002 Danum Valley Sabah-web.jpg
  • Polyrhachis Shattuck 53009 Danum Valley Sabah-web.jpg
  • Polyrhachis Shattuck 53048 Danum Valley Sabah-web.jpg
  • Polyrhachis Shattuck 53065 Danum Valley Sabah-web.jpg

Identification

Bolton (1973) - Worker. Monomorphic, medium to large (4.4 to 14.1 mm) ants belonging to the formicine tribe Camponotini. Antennae 12-segmented, the scapes inserted some distance behind the posterior clypeal margin (usually a distance greater than the basal width of the scape). Palp formula 6,4; mandibles usually with five, rarely with four teeth. Eyes well developed. Pronotum armed with a pair of spines, teeth or tubercles in all species of the Ethiopian region, the propodeum usually armed with two spines, teeth or tubercles, or a pair of ridges, rarely with only a single transverse ridge or completely unarmed. Promesonotal suture usually present (absent from khepra ), the development of the metanotal groove variable. Mesoscutellum very rarely present. In the single species in which the mesoscutellum occurs on the dorsum of the alitrunk, it is not separated from the scutum by a deep impression. Margination of the alitrunk variable, often present and complete but showing all stages through to a fully immarginate condition. Petiole usually with four but occasionally with two or six spines or teeth of variable configuration. Gaster large, globose, the first tergite extensive, usually forming at least half of the dorsal surface. The anterior face of the first gastral tergite is often truncated or concave. Acidopore not borne upon a conical projection of the hypopygium, usually concealed by the pygidium when not in use. Queen. As worker but with the alitrunk massively developed and with a corresponding reduction in armament and margination. The petiolar spines tend to be reduced and are usually smaller than those of the associated worker. Ocelli are present and wing venation is of the usual camponotine form. Male. Very poorly known, in most cases indistinguishable from the males of Camponotus.

Keys including this Genus

Keys to Species in this Genus

See the nomenclature section below for links to more Polyhrachis keys.

Distribution

World distribution based on political regions. View/Edit Data
Polyrhachis Distribution.png Worlddistribution legend.jpg

Species richness

Species richness by country based on regional taxon lists (countries with darker colours are more species-rich). View Data

Polyrhachis Species Richness.png

Biology

Bolton (1973) - The nesting habits of the genus as a whole have been discussed by Hung (1967) who sums up by saying that four types may be recognised, as follows:

1. Arboreal: carton and silk nests amongst leaves and twigs.

2. Lignicolous: nests in the cavities of plants.

3. Terrestrial: nests on the ground under any object.

4. Subterranean: nests in the soil, without cover.

Africa

Bolton (1973) - All four nesting types (see above) are found in the Ethiopian regional fauna. Obviously, the first on the list is more or less restricted to forest species whilst the third and fourth are most commonly found in savannah forms. The second type listed above is rather a broad category and as far as the Ethiopian region is concerned includes such diverse nest sites as those of Polyrhachis decemdentata in rotten or termite-mined tree branches and those of Polyrhachis cubaensis inside stem galls. It would probably also hold Polyrhachis otleti which nests in rot holes or crevices in tree trunks and covers the entrance with a mesh of silk and vegetable fibres.

The distribution of the species may be divided roughly into forest and savannah forms although some may penetrate the edges of one from the other. The species Polyrhachis viscosa and Polyrhachis schistacea may be considered as typical of the savannah forms, spreading throughout the continent; the former even occurs on the coastal plains of West Africa. Nests are constructed in the earth and the ants are fast-moving, ascending grasses and bushes to forage. The forest species are typified by Polyrhachis militaris and Polyrhachis decemdentata, arboreal retiring forms foraging singly upon the trees and with a marked tendency to release their grip and fall into the undergrowth if disturbed.

Spider Mimics

A Polyrhachis Ant mimicking spider, Trivandrum, India, Kalesh Sadasivan.jpg

A Polyrhachis-mimicking spider from Trivandrum, India. Photo by Kalesh Sadasivan.

Castes

Phylogeny

(Mezger & Moreau 2015) Spiny ants (Polyrhachis Smith) are a hyper-diverse genus of ants distributed throughout the Palaeotropics and the temperate zones of Australia. To investigate the evolution and biogeographic history of the group, we reconstructed their phylogeny and biogeography using molecular data from 209 taxa and seven genes. Our molecular data support the monophyly of Polyrhachis at the generic level and several of the 13 recognized subgenera, but not all are recovered as monophyletic. We found that Campomyrma Wheeler consists of two distinct clades that follow biogeographic affinities, that the boundaries of Hagiomyrma Wheeler are unclear depending on the analysis, that Myrma Billberg might be treated as one or two clades, and that Myrmhopla Forel is not monophyletic, as previously proposed. Our biogeographic ancestral range analyses suggest that the evolution of Polyrhachis originated in South-East Asia, with an age of the modern crown-group Polyrhachis of 58 Ma. Spiny ants dispersed out of South-East Asia to Australia several times, but only once to mainland Africa around 26 Ma.

Morphology

Worker Morphology

 • Antennal segment count 12 • Antennal club absent-gradual • Palp formula 6,4 • Total dental count 5-6 • Spur formula 1 simple-pectinate, 1 simple-pectinate; 0, 0 • Eyes present • Scrobes absent • Sting absent

Nomenclature

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

  • POLYRHACHIS [Formicinae: Camponotini]
    • Polyrhachis Smith, F. 1857a: 58. Type-species: Formica bihamata, by original designation.
    • [Polyrhachis Shuckard, in Swainson & Shuckard, 1840: 172. Nomen nudum.]
    • Polyrhachis subgenus of Myrma: Wheeler, W.M. 1911c: 860; Wheeler, W.M. 1911f: 170.
    • [Myrma subgenus of Polyrhachis: Forel, 1915b: 106; Forel, 1917: 251; Wheeler, W.M. 1922a: 702, 993; Emery, 1925b: 198 (see note under Myrma).]
    • Subgenera of Polyrhachis (alphabetical order with synonyms indicated): nominal plus Aulacomyrma (= Johnia), Campomyrma, Chariomyrma, Cyrtomyrma, Hagiomyrma, Hedomyrma (= Dolichorhachis, = Morleyidris), Hemioptica, Hirtomyrma, Myrma (= Anoplomyrma, = Hoplomyrmus, = Pseudocyrtomyrma), Myrmatopa (= Irenea), Myrmhopla (= Cephalomyrma, = Florencea), Myrmothrinax (= Evelyna).
    • [All subgenera were given as provisional junior synonyms of Polyrhachis by Brown, 1973b: 178-184. The list was repeated in Hölldobler & Wilson, 1990: 19 with all subgenera listed as junior synonyms. They reverted to subgeneric status in Bolton, 1994: 50; see under individual entries. The entry of Chariomyrma, Hagiomyrma and Hedomyrma under the synonymy of Polyrhachis by Taylor & Brown, D.R. 1985: 131, is not considered as confirmation as the three subgenera all range outside the Austral Region.]
  • Polyrachis Arnold, 1924: 741, incorrect subsequent spelling.

Dorow (1995) provides the latest revision of the species into subgenera and species-groups. These hierarchical arranged names are not supported by any strong evidence that these groups between the genus and species level represent monophyletic units. Regardless, much of the framework for these names has been in place for some time and they do serve as a welcome convenience for organizing the complex diversity of species. Rudy Kohout has been revising species by geographic areas and within specific subgenera and species-groups for more than two decades. Kohout's ongoing taxonomic work has largely followed the arrangement of Dorow (1995) with some modifications becoming necessary as more species have been described.

Aulacomyrma - key to Polyrhachis (Aulacomyrma) species

Campomyrma

Chariomyrma

Cyrtomyrma - key to Australian Cyrtomyrma species

Hagiomyrma - key to Polyrhachis Hagiomyrma group species

Hedomyrma

Hemioptica - species key

Hirtomyrma

Myrma

Myrmatopa

Myrmhopla

Myrmothrinax

Polyrhachis

References

  • Agosti, D. 1991. Revision of the oriental ant genus Cladomyrma, with an outline of the higher classification of the Formicinae (Hymenoptera: Formicidae). Syst. Entomol. 16: 293-310 PDF (page 295, Polyrhachis in Formicinae, Formica genus group)
  • Arnold, G. 1924. A monograph of the Formicidae of South Africa. Part VI. Camponotinae. Ann. S. Afr. Mus. 14: 675-766 (page 741, Polyrhachis in Camponotinae, Camponotini; [Polyrachis Arnold, 1924: 741, incorrect subsequent spelling].)
  • Ashmead, W. H. 1905c. A skeleton of a new arrangement of the families, subfamilies, tribes and genera of the ants, or the superfamily Formicoidea. Can. Entomol. 37: 381-384 (page 384, Polyrhachis in Camponotinae, Polyrhachidini)
  • Bolton, B. 1973b. The ant genus Polyrhachis F. Smith in the Ethiopian region (Hymenoptera: Formicidae). Bull. Br. Mus. (Nat. Hist.) Entomol. 28: 283-369 (page 289, Key to Afrotropical species)
  • Bolton, B. 2003. Synopsis and Classification of Formicidae. Mem. Am. Entomol. Inst. 71: 370pp (page 123, Polyrhachis in Formicinae, Camponotini; [All subgenera were given as provisional junior synonyms of Polyrhachis by Brown, 1973b: 178-184. The list was repeated in Hölldobler & Wilson, 1990: 19 with all subgenera listed as junior synonyms. They reverted )
  • Brown, W. L., Jr. 1973b. A comparison of the Hylean and Congo-West African rain forest ant faunas. Pp. 161-185 in: Meggers, B. J., Ayensu, E. S., Duckworth, W. D. (eds.) Tropical forest ecosystems in Africa and South America: a comparative review. Wash (page 178-184, All subgenera given as provisional junior synonyms of Polyrhachis (unconfirmed).)
  • Dalla Torre, K. W. von. 1893. Catalogus Hymenopterorum hucusque descriptorum systematicus et synonymicus. Vol. 7. Formicidae (Heterogyna). Leipzig: W. Engelmann, 289 pp. (page 257, Polyrhachis in Camponotinae)
  • 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 1, Revision of subgenera)
  • Emery, C. 1895l. Die Gattung Dorylus Fab. und die systematische Eintheilung der Formiciden. Zool. Jahrb. Abt. Syst. Geogr. Biol. Tiere 8: 685-778 (page 772, Polyrhachis in Camponotinae, Camponotini)
  • Emery, C. 1925d. Hymenoptera. Fam. Formicidae. Subfam. Formicinae. Genera Insectorum 183: 1-302 (page 175, Polyrhachis in Formicinae, Camponotini)
  • Forel, A. 1878c. Études myrmécologiques en 1878 (première partie) avec l'anatomie du gésier des fourmis. Bull. Soc. Vaudoise Sci. Nat. 15: 337-392 (page 367, Polyrhachis in Camponotinae [Camponotidae])
  • Forel, A. 1886h. Études myrmécologiques en 1886. Ann. Soc. Entomol. Belg. 30: 131-215 (page 194, Polyrhachis in Camponotinae, Camponotini)
  • Forel, A. 1893b. Sur la classification de la famille des Formicides, avec remarques synonymiques. Ann. Soc. Entomol. Belg. 37: 161-167 (page 165, Polyrhachis in Camponotinae, Camponotini)
  • Forel, A. 1912j. Formicides néotropiques. Part VI. 5me sous-famille Camponotinae Forel. Mém. Soc. Entomol. Belg. 20: 59-92 (page 89, Polyrhachis in Camponotinae, Camponotini)
  • Forel, A. 1917. Cadre synoptique actuel de la faune universelle des fourmis. Bull. Soc. Vaudoise Sci. Nat. 51: 229-253 (page 251, Polyrhachis in Camponotinae, Camponotini)
  • Hung, A. C. F. 1967b. A revision of the ant genus Polyrhachis at the subgeneric level (Hymenoptera: Formicidae). Trans. Am. Entomol. Soc. 93: 395-422 (page 395, Revision of subgenera)
  • Mayr, G. 1862. Myrmecologische Studien. Verh. K-K. Zool.-Bot. Ges. Wien 12: 649-776 (page 652, Polyrhachis in Formicinae [Formicidae])
  • Mayr, G. 1865. Formicidae. In: Reise der Österreichischen Fregatte "Novara" um die Erde in den Jahren 1857, 1858, 1859. Zoologischer Theil. Bd. II. Abt. 1. Wien: K. Gerold's Sohn, 119 pp. (page 6, Polyrhachis in Formicinae [Formicidae])
  • Mezger, D. and Moreau, C. S. 2015. Out of South-East Asia: phylogeny and biogeography of the spiny ant genus Polyrhachis Smith (Hymenoptera: Formicidae). Systematic Entomology. 41:369–378. doi:10.1111/syen.12163
  • Robson, S. K. A.; Kohout, R. J.; Beckenbach, A. T.; Moreau, C. S. 2015. Evolutionary transitions of complex labile traits: silk weaving and arboreal nesting in Polyrhachis ants. Behavioral Ecology and Sociobiology 69:449-458. PDF
  • Smith, F. 1857a. Catalogue of the hymenopterous insects collected at Sarawak, Borneo; Mount Ophir, Malacca; and at Singapore, by A. R. Wallace. [part]. J. Proc. Linn. Soc. Lond. Zool. 2: 42-88 (page 58, Type-species: Formica bihamata, by original designation.)
  • Smith, F. 1858a. Catalogue of hymenopterous insects in the collection of the British Museum. Part VI. Formicidae. London: British Museum, 216 pp. (page 58, Polyrhachis in Formicidae)
  • Swainson W.; Shuckard, W. E. 1840. On the history and natural arrangement of insects. London: Longman, Brown, Green & Longman's, 406 pp. (page 172, Polyrhachis Shuckard; nomen nudum)
  • Taylor, R. W.; Brown, D. R. 1985. Formicoidea. Zool. Cat. Aust. 2:1- 149: 1-149, 30 (page 131, The entry of Chariomyrma, Hagiomyrma, and Hedomyrma under the synonymy of Polyrhachis, is not considered as confirmation as the three subgenera all range outside the Australasian Region.)
  • Wheeler, W. M. 1910b. Ants: their structure, development and behavior. New York: Columbia University Press, xxv + 663 pp. (page 144, Polyrhachis in Camponotinae, Camponotini)
  • Wheeler, W. M. 1911c. Three formicid names which have been overlooked. Science (N. Y.) (n.s.) 33: 858-860 (page 860, Polyrhachis subgenus of Myrma)
  • Wheeler, W. M. 1922i. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. VII. Keys to the genera and subgenera of ants. Bull. Am. Mus. Nat. Hist. 45: 631-710 (page 701, Polyrhachis in Formicinae, Camponotini)
  • 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 993, Myrma subgenus of Polyrhachis)
  • Wheeler, W. M. 1911c. Three formicid names which have been overlooked. Science (N. Y.) (n.s.) 33: 858-860 (page 860, Polyrhachis subgenus of Myrma)
  • 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 993, Myrma subgenus of Polyrhachis)