Key to Australian Orectognathus Species

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The following key to Australian Orectognathus is based on Taylor (1977[1], 1978[2], 1980[3]).


  • Petiolar node rounded in general outline, completely lacking dorsolateral spines, denticles or other armament in addition the body and limbs sometimes bear abundant, generally distributed, fine, short erect pilosity => 2
  • Petiolar node either armed with a pair of prominent dorsolateral spines or teeth, or more or less prismatic in form, with an obtuse transverse crest bearing, usually distinct, dorsolateral denticles or angles (no known species of the latter group has generally distributed pilosity as described above) => 3


  • Outline of thoracic dorsum, in side view, complex; mesonotal section inflated, raised above pronotum and bearing a pair of erect dorsolateral spines or teeth, which supplement those of the pronotal humeri and propodeum => 4
  • Thoracic outline less complex, promesonotal profile evenly curved; no trace of mesonotal spines, though those of pronotum and propodeum are distinctly developed => 5


  • Occipital lobes each with a frontally directed tooth or spine which is either drawn out from the apex of the lobe or stands more or less free on its anterior face => Orectognathus satan
  • Occipital lobes bluntly rounded posteriorly and lacking any trace of frontally directed teeth or spines => 6


  • Scapes reaching or minutely exceeding apices of occipital lobes when laid back along head; length of humeral spines slightly exceeding maximum eye diameter; propodeal spines about 3 X as long as the distance between the centres of their bases => Orectognathus sexspinosus
Orectognathus sexspinosus casent0909302 h 1 high.jpg
Orectognathus sexspinosus casent0909302 p 1 high.jpg
  • Scapes, when laid back, clearly failing to reach occipital lobes by several times their maximum thickness; length of humeral spines only about 1/3 maximum eye diameter; propodeal spines only 1.5 X as long as the distance between the centres of their bases => Orectognathus elegantulus
Orectognathus elegantulus casent0900019 h 1 high.jpg
Orectognathus elegantulus casent0900019 p 1 high.jpg


  • Body and legs lacking erect pilosity (although a very few scattered hairs may be present) => 7
  • Body and legs with numerous fine short erect hairs => 8


  • Anteocular teeth developed and normally strong, their apices acute or at least right-angled; head averaging broader, CI 79-97 only rarely less than 81 => 9
  • Anteocular teeth lacking or representing only by an obtuse angle on each frontal carina; head narrower, CI normally 67-80 => 10


  • Mandibles converging towards their tips when closed, the inner borders lacking any trace of dentiform angles basad of apical teeth => Orectognathus coccinatus
  • Mandibles approximately parallel when closed, the inner border of each mandible, just basad of apical teeth, with a small tooth or dentiform angle => 11


  • Occipital lobes and frons behind anteocular teeth bearing scattered foveae spaced on average at nearly 1.5 X their average diameter, nearest neighbours only very rarely separated by less than one-half their average diameter; postpetiolar dorsum generally smooth at best with only feeble traces of puncturation => Orectognathus rostratus
Orectognathus rostratus casent0914673 h 1 high.jpg
Orectognathus rostratus casent0914673 p 1 high.jpg
  • Foveae of frons and occipital lobes more dense, average separation only about one-half their average diameter, nearest neighbours often separated by mere ridges, less than one-quarter their average diameter; postpetiolar dorsum with distinct foveate punctures => Orectognathus nanus
Orectognathus nanus casent0900016 h 1 high.jpg
Orectognathus nanus casent0900016 p 1 high.jpg


  • Dorsal surface of head smooth and shining, with minute punctures or small, spaced foveae; dorsal surface of gaster with a fine but distinct more or less reclinate, pubescence-like pilosity => 12
  • Dorsal surface of head covered with coarse, crowded and often contiguous foveae, the integument consequently subopaque to opaque; dorsal surface of gaster with only an extremely fine and sparse, appressed, pubescence-like pilosity (workers more or less polymorphic) => 13


  • Inner mandibular border just basad of apical teeth with a small dentiform angle, acute to subacute at tip => Orectognathus howensis

  • Inner mandibular border without an acute or subacute tooth-like angle in the region just basad of the apical teeth, though some species have a rounded flange or thickening in this region => 14


  • Propodeal spines reduced to small teeth, maximally (in larger specimens) about one-half as long as the distance separating the centres of their bases, and barely larger than the anteocular teeth (in very small specimens the propodeal teeth may be represented only by a pair of low, narrow longitudinal welts) => Orectognathus parvispinus
Orectognathus parvispinus casent0900017 h 1 high.jpg
Orectognathus parvispinus casent0900017 p 1 high.jpg
  • Propodeal spines elongate, approximately as long as the distance between the centres of their bases => 15


  • Dorsal surface of head smooth and shining, with only the most minute and inconspicuous of punctulae; postpetiole about 1.5 x as broad as long, broader anteriorly than behind => Orectognathus phyllobates
  • Dorsal surface of head smooth and shining, but sown with numerous circular, umbilicate foveae; postpetiole only slightly broader than long, with convex sides, not or scarcely broader in front than behind => Orectognathus nigriventris


  • Inner mandibular borders approximately straight along basal two-thirds; polymorphism of workers extending to a very large-headed, broad-jawed soldier form in addition to more 'normal' minor workers => Orectognathus versicolor
Orectognathus versicolor casent0106002 h 1 high.jpg
Orectognathus versicolor casent0106002 p 1 high.jpg
  • Inner mandibular borders shallowly but distinctly concave along basal two-thirds; worker polymorphism not extending to an extreme large-headed, broad-jawed soldier form => Orectognathus clarki
Orectognathus clarki casent0900020 h 1 high.jpg
Orectognathus clarki casent0900020 p 1 high.jpg


  • Head, thorax and nodes almost entirely covered by fine raised reticulate rnicrosculpture which overlies the basic foveate macrosculpture; foveae distinct on head but obscure and usually with elaborate outlines over much of thorax and nodes; gastral dorsum obscurely reflective, bearing finely incised micro-reticulate sculpture => Orectognathus mjobergi
Orectognathus mjobergi casent0010813 h 1 high.jpg
Orectognathus mjobergi casent0010813 p 1 high.jpg
  • Head, thorax and nodes carrying numerous spaced circular foveae of simple outline; the intervening surfaces smooth, shining and lacking clearly defined microsculpture, though faint traces may be present; gastral dorsum smooth and highly reflective => 16


  • Spines of pronotal humeri very small, scarcely larger than anteocular denticles. Central E Queensland => Orectognathus alligator
  • Pronotal spines not markedly reduced in size => 17


  • Head relatively narrow (Cl 67-69); lamellae lining inner borders of mandibular shafts only very slightly expanded just basad of the apical teeth; postpetiole distinctly longer than wide => Orectognathus darlingtoni
Orectognathus darlingtoni casent0900012 h 1 high.jpg
Orectognathus darlingtoni casent0900012 p 1 high.jpg
  • Head relatively broad (Cl 75-80); lamellae of inner mandibular borders distinctly expanded just basad of apical teeth; postpetiole at most only slightly longer than wide => Orectognathus antennatus
Orectognathus antennatus casent0172360 head 1.jpg
Orectognathus antennatus casent0172360 profile 1.jpg


Orectognathus robustus casent0900018 h 1 high.jpg
Orectognathus robustus casent0900018 p 1 high.jpg


  1. Taylor, R.W. (1977) New ants of the Australasian genus Orectognathus, with a key to the known species (Hymenoptera: Formicidae). Australian Journal of Zoology, 25, 581–612.
  2. Taylor, R.W. (1978). A taxonomic guide to the ant genus Orectognathus (Hymenoptera: Formicidae). Commonwealth Scientific and Industrial Research Organization (Australia) Division of Entomology Report, 3, 1–11.
  3. Taylor, R.W. (1980). New Australian ants of the genus Orectognathus, with summary description of the twenty-nine known species (Hymenoptera: Formicidae). Australian Journal of Zoology, 27, 773–788.