Plectroctena mandibularis

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This species is a specialized predator of millipedes.

At a Glance • Ergatoid queen  


Plectroctena mandibularis
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Ponerinae
Tribe: Ponerini
Genus: Plectroctena
Species: P. mandibularis
Binomial name
Plectroctena mandibularis
Smith, F., 1858

Plectroctena mandibularis sam-hym-c007208a profile 1.jpg

Plectroctena mandibularis sam-hym-c007208a dorsal 1.jpg

Specimen Label



Keys including this Species


Distribution based on Regional Taxon Lists

Afrotropical Region: Angola, Botswana, Cameroun, Democratic Republic of Congo, Ethiopia, Kenya, Malawi, Mozambique, Namibia, Rwanda, South Africa (type locality), Uganda, United Republic of Tanzania, Zambia, Zimbabwe.

Distribution based on AntMaps


Distribution based on AntWeb specimens

Check data from AntWeb


Colonies have less than 300 workers and one ergatoid queen (Villet 1990). Ergatoid queens have been observed to mate away from natal nests, after which they presumably founded a colony independently. Solitary queens with eggs and larvae were found under rocks (Villet 1999). In one such incipient nest, a dismembered milipede is evidence that foundresses hunt outside the nest. Ergatoid queens are typically associated with colony fission in ants, thus non-claustral independent colony foundation in P. mandibularis is unusual.

Workers lay trails with their stings while foraging, but these appear to be for personal orientation, because they never recruited nestmates to prey. However, workers laid trails when recruiting nestmates to new nest sites (Wilkins et al. 2006).

Foraging parties of 10-15 workers left nests and headed towards a particular area: they were led by one individual laying a trail on the ground. After a party broke up, the workers searched, captured and retrieved prey singly (Peeters & Crewe 1988).

Worker attempting to sting and paralyse a millipede in Mkuzi NP (KZN, South Africa). Photo by Christian Peeters
Worker single-handedly retrieving a freshly-caught millipede. Photo by Christian Peeters


The single ergatoid queen is not easily distinguished from nestmate workers, based on body size and slight anatomical differences.

Laboratory nest of P. mandibularis, showing slight dimorphism between the ergatoid queen (red arrow) and workers. From Gorongosa, Mozambique. Photo by Christian Peeters.
Comparison of thorax and petiole structure between worker and ergatoid queen (bottom). Only the first gaster segment is visible following dissection of ovaries. From Gorongosa, Mozambique. Photo by Christian Peeters.


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

  • mandibularis. Plectroctena mandibularis Smith, F. 1858b: 101, pl. 7, figs. 1-5 (m., ergatoid q., not w.) SOUTH AFRICA. Forel, 1913a: 108 (w.); Arnold, 1915: 86 (w.). Material of the nomen nudum caffra referred here: Roger, 1861a: 41. Senior synonym of major: Emery, 1899e: 469; Bolton, 1974c: 330; of integra and material of the unavailable name strialiventris referred here: Bolton, 1974c: 330; of conjugata: Villet, McKitterick & Robertson, 1999: 282. .
  • major. Plectroctena caffra r. major Forel, 1894b: 74 (ergatoid q., not w.) MOZAMBIQUE. Arnold, 1915: 86 (w.). Subspecies of mandibularis: Emery, 1911d: 95; Santschi, 1914b: 54. Junior synonym of mandibularis: Emery, 1899e: 469; Bolton, 1974c: 330.
  • conjugata. Plectroctena minor st. conjugata Santschi, 1914e: 8 (w.q.) SOUTH AFRICA. Santschi, 1924a: 166 (m.); Wheeler, G.C. & Wheeler, J. 1989b: 52 (l.). Raised to species: Santschi, 1924a: 166. Junior synonym of mandibularis: Arnold, 1926: 209. Revived from synonymy: Bolton, 1974c: 326. Junior synonym of mandibularis: Villet, McKitterick & Robertson, 1999: 282.
  • integra. Plectroctena mandibularis var. integra Santschi, 1924a: 161 (w.m.) KENYA. Junior synonym of mandibularis: Bolton, 1974c: 330.

The following notes on F. Smith type specimens have been provided by Barry Bolton (details):

Plectroctena mandibularis

One syntype queen (ergatoid) and one syntype male in The Natural History Museum. Labelled “Port Natal. 58/13.” Acc. Reg.: “ 1858 no. 13. Port Natal. Purchased of Stevens. Collected by Gueinzius.”

In the original description Smith initially refers to the specimens as worker and male. He states, “worker not known” but goes on to say that the two were taken “in coitu.” The two The Natural History Museum specimens are certainly a male and an ergatoid queen. They were originally mounted on a single pin, the male above the ergatoid. The male has been remounted, separately.



  • Arnold, G. 1915. A monograph of the Formicidae of South Africa. Part I. Ponerinae, Dorylinae. Ann. S. Afr. Mus. 14: 1-159 (page 86, worker described)
  • Bolton, B. 1974c. A revision of the ponerine ant genus Plectroctena F. Smith (Hymenoptera: Formicidae). Bull. Br. Mus. (Nat. Hist.) Entomol. 30: 309-338 (page 330, Senior synonym of major)
  • Bolton, B. 1974c. A revision of the ponerine ant genus Plectroctena F. Smith (Hymenoptera: Formicidae). Bull. Br. Mus. (Nat. Hist.) Entomol. 30: 309-338 (page 330, Senior synonym of integra, and material of the unavailable name strialiventris referred here)
  • Emery, C. 1899d. Fourmis d'Afrique. Ann. Soc. Entomol. Belg. 43: 459-504 (page 469, Senior synonym of major)
  • Forel, A. 1913a. Fourmis de Rhodesia, etc. récoltées par M. G. Arnold, le Dr. H. Brauns et K. Fikendey. Ann. Soc. Entomol. Belg. 57: 108-147 (page 108, worker described)
  • Roger, J. 1861a. Die Ponera-artigen Ameisen (Schluss). Berl. Entomol. Z. 5: 1-54 (page 41, Material of the nomen nudum caffra referred here)
  • Smith, F. 1858a. Catalogue of hymenopterous insects in the collection of the British Museum. Part VI. Formicidae. London: British Museum, 216 pp. (page 101, pl. 7, figs. 1-5 male, ergatoid queen described)
  • Villet, M. 1991. Colony foundation in Plectroctena mandibularis F. SMITH, and the evolution of ergatoid queens in Plectroctena (Hymenoptera: Formicidae). Journal of Natural History 25: 979-983.
  • Villet, M. 1999. Reproductive behaviour of Plectroctena mandibularis F. SMITH (Hymenoptera: Formicidae), a ponerine ant with ergatoid queens. African Entomology 7: 289-291.
  • Wilkins, K.J., Harman K. & Villet, M. 2006. Recruitment behaviour in the ponerine ant Plectroctena mandibularis F. SMITH (Hymenoptera: Formicidae). African Entomology 14: 367-372.