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Orectognathus antennatus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Orectognathus
Smith, F., 1853
Type species
Orectognathus antennatus
29 species
(Species Checklist, Species by Country)

Orectognathus antennatus casent0172360 profile 1.jpg

Orectognathus antennatus

Orectognathus antennatus casent0172360 dorsal 1.jpg

Specimen label

Evolutionary Relationships

Ochetomyrmex (2 species), Tranopelta (2 species)

Allomerus (8 species), Blepharidatta (4 species), Diaphoromyrma (1 species), Lachnomyrmex (16 species), Wasmannia (11 species)

  (7 species)

  (2 species)

  (7 species)

  (4 species)

  (29 species)

  (16 species)

  (20 species)

  (9 species)

Acromyrmex (56 species), Apterostigma (44 species), Atta (20 species), Cyatta (1 species), Cyphomyrmex (23 species), Kalathomyrmex (1 species), Mycetophylax (21 species), Mycetagroicus (4 species), Mycetarotes (4 species), Mycetosoritis (2 species), Mycocepurus (6 species), Myrmicocrypta (31 species), Sericomyrmex (11 species), Trachymyrmex (9 species), Xerolitor (1 species)

Basiceros (9 species), Cephalotes (123 species), Eurhopalothrix (55 species), Octostruma (35 species), Phalacromyrmex (1 species), Pheidole (1,293 species), Pilotrochus (1 species), Procryptocerus (44 species), Protalaridris (7 species), Rhopalothrix (16 species), Strumigenys (859 species), Talaridris (1 species)

Based on Ward et al. (2014), Blaimer et al. (2018) and Li et al. (2018).

Bolton 2000 - What little is known of the general biology is summarised by Brown (1953). Of the 29 described species (Taylor, 1980) one, Orectognathus versicolor, has evolved worker polymorphism. Division of labour in this species has been studied by Carlin (1982) and contrasted with the worker polyethism described by Wilson (1962) in the polymorphic Daceton armigerum. Holldobler (1982) has shown that O. versicolor is also a trail-layer, a rare feature among the dacetines.

At a Glance • Trap-Jaw  



Heterick (2009) - Workers with five-segmented antenna, with the third segment much more elongate than the remaining segments of the flagellum. The mandibles are of the trap-jaw variety, long and thin.

AntWeb icon 02.png See images of species within this genus

Keys including this Genus


Keys to Species in this Genus


Distribution and Richness based on AntMaps


Life History Traits

  • Mean colony size: "usually less than 60" to 104 (Greer et al., 2021)
  • Compound colony type: not parasitic (Greer et al., 2021)
  • Nest site: hypogaeic (Greer et al., 2021)
  • Diet class: predator (Greer et al., 2021)
  • Foraging stratum: subterranean/leaf litter (Greer et al., 2021)
  • Foraging behaviour: cooperative (Greer et al., 2021)



Worker Morphology

 • Eyes: 11->100 ommatidia • Pronotal Spines: dentiform; present • Mesonotal Spines: absent; dentiform • Propodeal Spines: dentiform; present • Petiolar Spines: absent • Caste: none or weak • Sting: present • Metaplural Gland: present • Cocoon: absent


All Karyotype Records for Genus

Explore Data: All, Drilldown
Click here to show/hide karyotype data.
Taxon Haploid Diploid Karyotype Locality Source Notes
Orectognathus clarki 30 Australia Crozier, 1968d
Orectognathus darlingtoni 11 22 Australia Imai et al., 1977
Orectognathus versicolor 11 22 Australia Imai et al., 1977


The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

  • ORECTOGNATHUS [Myrmicinae: Dacetini]
    • Orectognathus Smith, F. 1853: 227. Type-species: Orectognathus antennatus, by monotypy.
    • Orectognathus senior synonym of Arnoldidris: Taylor, 1977: 581; Bolton, 1999: 1655; Bolton, 2000: 19.
  • ARNOLDIDRIS [junior synonym of Orectognathus]
    • Arnoldidris Brown, 1950c: 143. Type-species: Orectognathus chyzeri, by original designation.
    • Arnoldidris junior synonym of Orectognathus: Taylor, 1977: 581; Bolton, 1999: 1655.

Bolton (2000) - Workers Mandibles linear and elongate, with kinetic mode of action , each with an apical fork of 3 spiniform teeth that interlock at full closure. Mandibles at full gape open to 170 degrees or more. Basal process of mandible a curved spur; at full mandibular closure process is dorsal to labrum and fits into a mediodorsal impression on labrum. Palp formula 5, 3. Labrum roughly T-shaped , short and not capable of reflexing to conceal the labio-maxillary complex , which is permanently exposed. Each lateral labral arm locks into a deep emargination near the inner mandibular base. A single long trigger hair arises from each transverse arm of the T-shaped labrum. Eye not located ventrolaterally on side of head. Antenna with 5 segments, of which the second funicular segment (= third antennal) is an elongate bar-like fusion segment; with a weakly differentiated apical club of 2 segments. Scape, when laid back in its normal resting position , passes above the eye; apical portion of extended scape not to distinctly curved anteriorly when seen in full-face view; scape slightly downcurved near base. Scrobe absent to weakly present. Pronotal humeri and mesonotum armed or unarmed, the former more usual. Propodeal spiracle well in front of margin of declivity, at approximately the midheight of the sclerite. Metapleural gland bulla small, with its apex widely separated from the propodeal spiracle. Waist segments without spongiform tissue and without lateral laminar cuticular processes; petiole node unarmed to bidentate; postpetiolar spiracle lateral. Limbus absent from first gastral tergite; suture between first gastral tergite and sternite rounded laterobasally; basigastral costulae absent.

Baroni Urbani & De Andrade (2007) - Only one, convincing, synapomorphy is known for this genus: the hypertrophy of the second funicular joint of workers and gynes (CI 1.00, RI 0.00).


(page 161, Orectognathus in Poneridae, Myrmicidae)
  • Taylor, R. W. 1977. New ants of the Australasian genus Orectognathus, with a key to the known species (Hymenoptera: Formicidae). Aust. J. Zool. 25: 581-612 (page 581, Orectognathus senior synonym of Arnoldidris; page 585, Revision of genus)
  • Taylor, R. W. 1978b. A taxonomic guide to the ant genus Orectognathus (Hymenoptera: Formicidae). CSIRO Div. Entomol. Rep. 3: 1-11 (page 1, Revision of genus)
  • Wheeler, W. M. 1910b. Ants: their structure, development and behavior. New York: Columbia University Press, xxv + 663 pp. (page 141, Orectognathus in Myrmicinae, Dacetini)
  • 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 666, Orectognathus in Myrmicinae, Dacetini)