Camponotus postcornutus

This species is ground nesting with a simple entrance hole. It is most common in south-western Western Australia with a single collection from South Australia which is lighter in colour than those from Western Australia. Material is mostly from relatively dry areas such as mallee. Camponotus postcornutus is striking red-and-black ant is a diurnal forager, and both major and minor workers can be seen scurrying quickly over the ground in mallee country.

Identification
In minor workers, the pronotum, mesonotum and dorsum of propodeum form a strong, even convexity, the metanotal groove is absent and the posterior face of the propodeum is only weakly differentiated from the dorsal face. The posterior corners of the head in major workers taper rearward into blunt protuberances. The shape of the mesosoma and the cephalic protuberances in major workers will separate this species from close relatives.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 * . Camponotus (Tanaemyrmex) postcornutus Clark, 1930a: 121, fig. 1 (nos. 7,8) (s.w.) AUSTRALIA (Western Australia).
 * Wheeler, G.C. & Wheeler, J. 1974a: 62 (l.).
 * Status as species: Taylor & Brown, 1985: 118; Taylor, 1987a: 14; Bolton, 1995b: 118; Shattuck & McArthur, 2002: 77 (redescription); McArthur, 2007a: 310; Heterick, 2009: 61; McArthur, 2014: 158.

Major worker
Medial section of anterior clypeal margin weakly projecting anteriorly with broad lateral angles and a feeble medial concavity; carina distinct. Posterior corners of head produced as blunt horns in major and medium workers. Pronotum, mesonotum and metanotum form an even convexity, propodeal dorsum and posterior face form a separate even convexity without angle. Anterior face of petiolar node convex, summit moderately sharp, posterior face straight. Dorsal and undersides of head, mesosoma, petiole, gaster and coxa with sparse reddish, long erect setae. Entire body dark red-brown with the gaster darker.

Minor worker
Anterior clypeal margin projecting weakly, carina sharp. Pronotum, mesonotum and dorsum of propodeum form a reasonably even convexity; propodeal angle broadly rounded, posterior face straight, ratio of dorsum to declivity about 2. Anterior face of petiolar node convex, summit bluntly rounded, posterior face convex. Dorsal and undersides of head, mesosoma, petiole, gaster and coxa with sparse reddish long erect setae. Entire body dark red-brown with the gaster darker.

Measurements
Workers (n=8). CI 1.06 — 1.18; HL 1.95mm — 4.16mm; I4W 2.06mm — 4.89mm; ML 3.28mm — 4.90mm; MTL 2.16mm — 2.84mm; PnW 1.71mm — 3.13mm; SI 0.57 — 1.14; SL 2.35mm — 2.77mm.

Worker major.-Length, 13-14.5 mm.

Blood red. Gaster black. Mandibles and scapes brown. Shining. Mandibles coarsely punctate. Head, thorax and node microscopically reticulate, the occipital border smooth and polished. Gaster microscopically striate transversely. The whole body interspersed with fine shallow punctures. Hair reddish, long and erect, very sparse throughout, except on the apical segments of the gaster. Pubescence very fine and sparse, noticeable only on the antennae and legs. The tibiae, and tarsi have two rows of stout sharp bristles on the under side. Head large, much broader than long, broadest at the eyes, the occipital border truncate, straight, or very feebly concave, the sides strongly convex, the inferior posterior angles greatly produced backward and slightly outward as short blunt horns. Frontal carinae short, diverging widely behind, there is a well defined longitudinal groove between them extending to the anterior ocellus, where it is deepest. Clypeus broad, convex, feebly carinate, the anterior border produced, straight in the middle; there is a moderately deep fovea on each side near the middle. Eyes large, rather flat, placed at the posterior third of the sides. Ocelli very small, the anterior largest. Scapes extending beyond the occipital border by barely twice their thickness, second and third segments of the funiculus of equal length, longer than the first. Mandibles broad, armed with six large sharp teeth. Thorax one and one third times longer than broad. Pronotum three times broader than long, convex in front and on the sides, the anterior border sharply margined, the margin reflexed, extending to the anterior third of the sides. Mesonotum broader than long, convex above. The metanotum shown as a distinct segment, the sutures rather feeble. Epinotum longer than broad, strongly convex laterally; in profile the dorsum and declivity united in an even arch. The whole thorax is strongly convex longitudinally, the mesonotum sharply marginate below. Node fully twice as broad as long, all four sides convex, the dorsum contracting to a bluntly rounded top edge which is sharply notched in the middle;  profile barely twice as high as long, bluntly pointed above. Gaster longer than broad. Legs robust. Worker minor.-Length, 8.5-10 mm. Color, sculpture and pilosity as in the major. Head slightly broader than long, broader behind than in front, the inferior posterior angles sharp, not strongly produced as in the major. Clypeus more sharply carinate. Scapes extending beyond the occipital border by half their length. Pronotum and mesonotum similar. Metanotum not defined. Epinotum slender, almost sharp on top. Node thicker, rounded, not notched on top; in profile it is convex above. The rest as in the major. Habitat.-Western Australia: Bungulla (T. Greaves; J. Clark). The shape of the head and thorax separate this from all the other Australian species. The major and minor workers are found hunting on the ground and on tree trunks, all day long. They are very active and pugnacious.

References based on Global Ant Biodiversity Informatics

 * Heterick B. E. 2009. A guide to the ants of south-western Australia. Records of the Western Australian Museum Supplement 76: 1-206.
 * Shattuck S. O., A . J. McArthur. 2002. A taxonomic revision of the Camponotus wiederkehri and perjurus species-groups (Hymenoptera: Formicidae). Transactions of the Royal Society of South Australia 126: 63-90.