Chelaner rufoniger

This ant occupies a variety of habitats, from mallee to Callitris scrub. In the southwest of Western Australia the species is quite common, and is found within the Perth metropolitan area. Outside of Western Australia the ant is known from single collections (i.e. Tarcoola, South Australia, and Barooga, New South Wales).

Identification
Heterick (2001) - A member of the bicorne group. Chelaner rufonigrum, as here described, may not be monophyletic. The workers of some series are dark brown to black, with a narrow and highly sculptured petiolar node, and the head capsule (viewed dorsally) is no broader than the promesonotum. The workers of Chelaner rufonigrum sensu stricto are red and black, the node is thicker with simple rugosity, and the head capsule (viewed dorsally) is broader than the promesonotum, at least in the major and media workers. Because of some variability of colour in the small, dark specimens, and the lack of comprehensive nest collections with good representation of different-sized workers, this variation may still fall within intraspecific boundaries. Individual specimens are distinguishable from Chelaner striatifrons by the more angulate appearance of the propodeum, and often the colour, and from Chelaner majeri by the more robust sculpture.

Heterick (2009) - Possibly a species complex, but may equally be a single species with alternative phenotypes depending on alleles possessed by the colonies. Some colonies contain polymorphic workers (major and media workers red-and-black or uniformly brownish, smallest minor workers uniformly brown or bicoloured light and dark brown), while others seem to contain monomorphic workers (uniformly red-and-black or uniformly brown). The head of the red-and-black workers is relatively broader than that of workers of the latter type of colony, but the morphology of the minor workers is very similar for both types of colony.

Distribution
The ant is widespread in the SWBP, WA and the red- and-black form has been collected in the Perth metropolitan area. Populations also occur in NSW and SA.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  rufonigrum. Monomorium rufonigrum Heterick, 2001: 374, figs. 1-10, 12, 21, 179-181 (w.q.m.) AUSTRALIA.
 * Combination in Chelaner: Sparks et al., 2019: 233.

Worker
Holotype. HML 3.78; HL 1.30; HW 1.30; Cel 100; SL 0.92; SI 71; PW 0.82. Others. HML 1.57-3.88; HL 0.56-1.34; HW 0.51-1.34; Cel 85-107; SL 0.34-0.89; SI 60-79; PW 0.31-0.79 (53 measured).

Head. Head square or rectangular; vertex slightly concave; frons microreticulate and striolate with incurved decumbent and subdecumbent setulae, or longitudinally striate with combination of appressed setulae and erect and suberect setae. Compound eyes elliptical, or ovoid; (viewed from front) compound eyes set in anterior half of head capsule; (viewed laterally) compound eyes set at midline of head capsule; eye moderate, eye width 0.5-1.5x greatest width of antennal scape to large, eye width greater than 1.5 x greatest width of antennal scape. Antennal segments 12; club three-segmented. Anteromedial clypeal margin emarginate, median clypeal carinae produced apically as pair of pronounced teeth, or emarginate, median clypeal carinae produced apically as pair of pronounced teeth, with an additional tooth or denticle on either side, or emarginate, median clypeal carinae produced as pair of bluntly rounded denticles. Longest lateral anterior clypeal setae long, extending beyond dorsal margin of closed mandibles. Posteromedial clypeal margin level with posterior surface of antennal fossae. Anterior tentorial pits situated nearer antennal fossae than mandibular insertions. Frontal lobes parallel straight. Venter of head capsule without elongate, basket-shaped setae. Palp formula 2,3. Maximum number of mandibular teeth and denticles: four; mandibles (viewed from front) strap-like with inner and outer edges subparallel, striate, with piliferous punctures; basal tooth not enlarged; basal angle indistinct; apical and basal mandibular margins meeting in curve.

Alitrunk. Promesonotal sculpture present in form of microreticulation and rugosity over entire promesonotum; dorsal promesonotal face evenly convex; erect and suberect promesonotal setae greater than 10; setulae appressed. Mesonotal suture absent, or visible externally as faint ridge. Metanotal groove present as feebly impressed furrow between promesonotum and propodeum. Propodeal sculpture present as uniform microreticulation, with few or no striae or costulae, or present as uniform rugosity, with well defined costulae on declivitous face of propodeum; dorsal propodeal face flattened to sloping posteriad, with wedge-shaped flattening or shallow depression that is widest between propodeal angles; processes absent (propodeum smoothly rounded in profile or with slight hump at propodeal angle), or absent (propodeum angulate in profile), or present on posterior propodeal angles as small denticles or sharp flanges; lobes present as blunt flanges. Propodeal angle absent, or present; declivitous face of propodeum flat. Erect and suberect propodeal setae greater than 10; propodeal setulae absent, or appressed. Propodeal spiracle lateral and about midway between metanotal groove and declivitous face of propodeum; vestibule conspicuous through cuticle.

Petiole and postpetiole. Petiolar spiracle lateral and positioned in pedicel well anteriad of petiolar node. Petiolar node cuneate, dorsally rounded, or cuneate, sharply tapered; sculpture present in form of microreticulation. Ratio of greatest node breadth (viewed from front) to greatest node width (viewed in profile) near 4:3 to near 3:4. Anteroventral process present as pronounced spur, or slender carina that tapers posteriad. Ventral lobe present in some individuals. Height ratio of petiole to postpetiole near 1:1 to near 4:3; height-length ratio of postpetiole near 1:1 to near 3:4. Sculpture absent on dorsum, at least: postpetiole smooth and shining. Ventral process present and distinct.

Gaster. Pilosity of first gastral tergite consisting of combination of appressed setulae and longer, erect and suberect setae.

General characters. Colour of body either uniformly brown to dark chocolate with legs lighter in some individuals, or orange to dark russet with head and coxae dark brown to black, mandibles orange, gaster fulvous to black, and legs brown. Worker caste monomorphic but variable in size, with series of intercastes between largest and smallest workers (monophasic allometry).

Queen
HML 3.23-4.19; HL 1.01-1.35; HW 1.19-1.37; Cel 104-118; SL 0.83-0.93; SI 65-70; PW 0.78-0.93 (3 measured).

Head. Head square or rectangular; vertex slightly concave, or planar; frons longitudinally striate with combination of incurved decumbent and subdecumbent setulae and erect and suberect setae. Compound eyes elliptical; (viewed from front) compound eyes set in anterior half of head capsule; (viewed laterally) compound eyes set at midline of head capsule; eye large, eye width greater than 1.5 x greatest width of antennal scape.

Alitrunk. Mesoscutum in profile convex anteriad; thereafter flattened, or evenly flattened. Mesoscutal pilosity consisting of decumbent and subdecumbent setulae anteriad and erect and suberect setae posteriad; dorsal appearance of mesoscutum smooth and shining; length-width ratio of mesoscutum and scutellum combined near 4:3. Axillae separated by distance of about half greatest width of scutellum. Propodeal sculpture present as uniform rugosity, with well-defined costulae on declivitous face of propodeum; dorsal propodeal face flattened. Propodeal processes absent (propodeum angulate in profile); lobes present as blunt flanges. Propodeal angle present. Erect and suberect propodeal setae greater than 1 0; propodeal setulae decumbent and subdecumbent. Propodeal spiracle lateral and nearer metanotal groove than declivitous face of propodeum.

Wing. Wing veins tubular and strongly sclerotised; vein m-cu present as an entire vein enclosing first discoidal cell; vein cu-a present.

Petiole and postpetiole. Petiolar spiracle lateral and positioned in pedicel well anteriad of petiolar node. Petiolar node tumular; sculpture present in form of microreticulation. Ratio of greatest node breadth (viewed from front) to greatest node width (viewed in profile) near 1:1. Anteroventral process distinct in some individuals as slender carina that tapers posteriad. Height ratio of petiole to postpetiole near l:l to near 4:3; height-length ratio of postpetiole near 4:3 to near 1:1. Sculpture present in form of microreticulation; ventral process absent or vestigial, or present and distinct.

Gaster. Pilosity of first gastral tergite consisting entirely of erect and suberect setae.

General characters. Colour of alitrunk, petiole and postpetiole orange to crimson; variously infuscated with dark brown; gaster and head brown to black. Brachypterous alates not seen. Ergatoid or worker-female intercastes not seen.

Male
HML 1.91-4.09; HL 0.47-0.93; HW 0.47-1.03; CeI 97-111; SL 0.18-0.31; SI 25-44; PW 0.52-1.16 (12 measured).

Head. Head width-mesoscutal width ratio near 1:1. Compound eyes protuberant and elliptical; (viewed laterally) compound eyes set at midline of head capsule; ocelli conspicuous and turreted. Ratio of length of first funicular segment of antenna to length of second funicular segment near 1:3 to near 1:4. Maximum number of mandibular teeth and denticles: three.

Alitrunk. Mesoscutum in profile convex anteriad; thereafter flattened; dorsal appearance of meso scutum finely microreticulate; mesoscutal pilosity consisting of long, dense setae. Parapsidal furrows present and distinct; notauli absent. Axillae separated by distance less than half greatest width of scutellum, or separated by distance more than half greatest width of scutellum.

Wing. Wing veins tubular and strongly sclerotised; vein m-cu present as an entire vein enclosing first discoidal cell; vein cu-a present.

Petiole and postpetiole. Petiolar spiracle lateral and positioned in pedicel well anteriad of petiolar node. Sculpture present in form of microreticulation, or present; petiolar node rugose; ratio of greatest node breadth (viewed from front) to greatest node width (viewed in profile) near 3:4. Anteroventral process always absent or vestigial; ventral lobe present in some individuals. Height-length ratio of postpetiole near 1:1; sculpture present in form of microreticulation, or present; postpetiole rugose; ventral process absent or vestigial, or present and distinct.

Gaster. Pilosity of first gastral tergite consisting mainly of decumbent and subdecumbent setulae.

General characters. Colour of body chocolate, legs and gaster brown to dark brown.

Type Material
Holotype. Worker, Western Australia, Meekatharra, 20 May 1967, C. Mercovich, golf course, ANIC vial no. 66-43. Paratypes. Western Australia: 1 queen, 1 male, 4 workers, The Granites, Meekatharra, 23.v.l967, C. Mercovich (ANIC); I o, 2 workers, The Granites, Meekatharra, ANIC vial no. 66-41 (ANIC); 3o, 5 workers, Mount Magnet area, 20 May 1967, C. Mercovich, golf course, ANIC vial 66.43 ; 8 workers (I missing head), Mount Magnet area, 19.v.l967, C. T. Mercovich.



Etymology
Latin: “red-and-black”.