Plectroctena mandibularis

This species is a specialized predator of millipedes.

Distribution based on Regional Taxon Lists
Afrotropical Region: Angola, Botswana, Cameroun, Democratic Republic of Congo, Ethiopia, Kenya, Malawi, Mozambique, Namibia, Rwanda, South Africa, Uganda, United Republic of Tanzania, Zambia, Zimbabwe.

Biology
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).

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

Nomenclature

 *  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.

Plectroctena mandibularis

One syntype queen (ergatoid) and one syntype male in. 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 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.

References based on Global Ant Biodiversity Informatics

 * Arnold G. 1915. A monograph of the Formicidae of South Africa. Part I. Ponerinae, Dorylinae. Annals of the South African Museum 14: 1-159.
 * Bolton B. 1974. A revision of the ponerine ant genus Plectroctena F. Smith (Hymenoptera: Formicidae). Bull. Br. Mus. (Nat. Hist.) Entomol. 30: 309-338.
 * Bolton B., and W. L. Brown Jr. 2002. Loboponera gen. n. and a review of the Afrotropical Plectroctena genus group (Hymenoptera: Formicidae). Bulletin of the Natural History Museum. Entomology Series 71: 1-18.
 * Emery C. 1892. Voyage de M. Ch. Alluaud dans le territoire d'Assinie (Afrique occidentale) en juillet et août 1886. Formicides. Annales de la Société Entomologique de France 60: 553-574.
 * Emery C. 1911. Hymenoptera. Fam. Formicidae. Subfam. Ponerinae. Genera Insectorum 118: 1-125.
 * Forel A. 1910. Zoologische und anthropologische Ergebnisse einer Forschungsreise im westlichen und zentralen Südafrika ausgeführt in den Jahren 1903-1905 von Dr. Leonhard Schultze. Vierter Band. Systematik und Tiergeographie. D) Formicidae. Denkschriften der Medizinisch-Naturwissenschaftlichen Gesellschaft zu Jena 16: 1-30.
 * Forel A. 1911. Fourmis nouvelles ou intéressantes. Bull. Soc. Vaudoise Sci. Nat. 47: 331-400.
 * 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
 * Lindsey P. A., and J. D. Skinner. 2001. Ant composition and activity patterns as determined by pitfall trapping and other methods in three habitats in the semi-arid Karoo. Journal of Arid Environments 48: 551-568.
 * Menozzi C. 1939. Hymenoptera Formicidae. Missione Biologica nel Paese dei Borana. 3: 97-110.
 * Santschi F. 1914. Meddelanden från Göteborgs Musei Zoologiska Afdelning. 3. Fourmis du Natal et du Zoulouland récoltées par le Dr. I. Trägårdh. Göteborgs Kungliga Vetenskaps och Vitterhets Samhälles Handlingar. 15: 1-44.
 * Santschi F. 1924. Revue du genre Plectroctena F. Smith. Revue Suisse de Zoologie 31: 155-173.
 * Santschi, F. "Résultats de la Mission scientifique suisse en Angola, 1928-1929. Formicides de l'Angola." Revue Suisse de Zoologie 37 (1930): 53-81.
 * Schoeman C. S., and S. H. Foord. 2012. A checklist of epigaeic ants (Hymenoptera: Formicidae) from the Marakele National Park, Limpopo, South Africa, Koedoe 54(1), Art. #1030, 7 pages. http://dx.doi.org/10.4102/koedoe.v54i1.1030
 * Stitz H. 1923. Hymenoptera, VII. Formicidae. Beiträge zur Kenntnis der Land- und Süsswasserfauna Deutsch-Südwestafrikas 2: 143-167.
 * Villet M. H., L. McKitterick, and H. G. Robertson. 1999. Systematic status of Plectroctena mandibularis Smith and P. conjugata Santschi (Hymenoptera: Formicidae: Ponerini). African Entomology 7: 277-284.
 * 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