Camponotus aurocinctus

Camponotus aurocinctus is ground nesting, shows a strong preference for sandy soils and is most often found as foragers during daylight hours on the ground or on low vegetation. It has observed at Stockyard Plain and Danggali Conservation Park, South Australia, foraging in the vicinity of Camponotus terebrans.



Identification
This species belongs to the C. wiederkehri species group. Members of this group can be separated from other Australian Camponotus by the presence of a cluster of four or more distinct elongate curved or “J”-shaped hairs on the base of the mentum (near the posterior region of the buccal cavity) in all worker castes. In a few species related to C. ephippium similar hairs are present but these are scattered along the length of the mentum rather than being present as a posterior cluster.

C. aurocinctus can be identified within this group be having the following characters:

Tibiae lacking erect hairs. In minors, metanotal groove depressed below the level of the anterior region of the propodeum; dorsal surface of petiolar node relatively long and flat, its anterior face much shorter than the posterior face. Mesosoma uniform in colour, varying from dark red-black to black, anterior region of first gastral tergite similar in colour to propodeum, gastral tergites often with the trailing edge golden yellow, the golden colour (when present) varying in width from a narrow band to involving most of the tergite.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  aurocinctus. Formica aurocincta Smith, F. 1858b: 39 (w.) AUSTRALIA. Viehmeyer, 1914b: 45 (s.). Combination in Camponotus: Mayr, 1886c: 355; in C. (Myrmosphincta): Forel, 1914a: 273; in C. (Myrmosaulus): Wheeler, W.M. 1922a: 705. Senior synonym of midas: Shattuck & McArthur, 2002: 67.
 * midas. Camponotus midas Froggatt, 1896: 390, pl. 27, figs. 6-9 (s.w.q.) AUSTRALIA. Combination in C. (Myrmophyma): Emery, 1925b: 111; in C. (Myrmosaulus): Clark, 1930c: 22. Junior synonym of aurocinctus: Shattuck & McArthur, 2002: 67.

Type Material


Camponotus midas, established by Froggatt (1896), is a synonym of C. aurocinctus. Froggatt made no mention of C. aurocinctus in his description of C. midas and it is unclear if he was aware of C. aurocinctus, and if so, how it differed from his species. Clark (1930a) redescribed C. midas and separated it from C. aurocinctus "by the shape of the thorax and node, and the colour of the gaster. In C. aurocincta the posterior margin of the segments is narrowly yellow. In midas the whole of the segments, except the base of the first, are entirely bright golden yellow." Unfortunately, the currently available material shows that all of these characters are highly variable. Many show an east-west clinal pattern, with several changing rapidly across central South Australia. For example, C. aurocinctus specimens from Western Australia are generally darker and hairier (especially on the underside of the head) compared to those from eastern South Australia eastward. The western populations also tend to have broader bands of golden yellow on the gaster with completely black gasters essentially unknown. In contrast, eastern populations often have narrow bands or lack banding completely, the gasters being uniformly black. Other characters, such as the depth of the metanotal groove and the relative length of the petiolar node, vary considerably within local areas or within single nest series. This variation suggests that a single widespread and variable species is involved rather than two (or more) separate species.

Description
Major worker. Anterior clypeal margin weakly convex. Dorsal surfaces of pronotum and mesonotum convex and separated by a shallow angle; propodeum uniformly convex and without a distinct angle; petiolar node with distinct anterior and posterior faces, its upper surface varying from a broad, blunt angle to uniformly convex and sometimes with the medial section nearly flat. Erect hairs absent from scapes, petiole and tibiae, absent or a few scattered hairs on the outline of head and dorsum of mesosoma and gaster; underside of head with none to about 30. Body varying from dark red to red-black, the head and dorsal surfaces of pronotum and mesonotum sometimes darker than the lateral mesonotum, propodeum, legs and petiole; gaster reddish black with yellow-gold banding along the posterior edge of each segment which varies from being absent to involving the entire visible portion of the segment.

Minor worker. Anterior clypeal margin convex to broadly angular. Dorsal surfaces of pronotum and mesonotum convex and separated by a shallow, broad angle, the posterior metanotum ending in the metanotal groove; metanotal groove distinct, separated from the anterior propodeum by a short face which varies from steep to gentle; dorsal and posterior faces of propodeum flat to weakly concave and separated by a broad, gentle angle. Anterior face of petiolar node short and separated from the dorsal face by a sharp angle, dorsal face elongate and flat to weakly concave and separated from the posterior face by a broad, rounded angle, posterior face flat. Erect hairs absent from scapes and legs, absent or with a few scattered hairs on the outline of head, mesosoma, petiole and gaster; underside of head with up to about 30 hairs. Body varying from red to red-black, head and sometimes propodeum, petiole and middle and hind legs usually slightly lighter than the pronotum; gaster dark reddish black and sometimes with yellow-gold banding along the posterior margin of each segment which varies from narrow to involving the entire visible segment, in which case the gaster is completely yellow-gold.

Measurements
Workers (n=20). CI 0.80 (minors) - 1.22 (majors); HL 2.04mm - 4.05mm; HW 1.63mm - 4.94mm; ML 3.68mm - 5.14mm; MTL 2.58mm - 3.14mm; SI 0.63 (majors) - 1.53 (minors); SL 2.50mm - 3.00mm


 * CI: Cephalic index: HW/HL.
 * HL: Maximum head length in full face view, measured from the anterior-most point of the clypeal margin to the midpoint of a line drawn across the posterior margin of the head.
 * HW: Maximum head width in full face view excluding the eyes.
 * ML: Mesosomal length measured from the anterior margin of the pronotal collar to the posterior extension of the propodeum lobes.
 * MTL: Maximum length of mid tibia, excluding the proximal part of the articulation which is received into the distal end of the femur.
 * SI: Scape index: SL/HW.
 * SL: Length of the scape (first antennal segment) excluding the basal neck and condyle.