Chelaner

Identification
Small to medium ants 2–7 mm in length, commonly monomorphic but with size variation in some species. Clypeus bicarinate with a median clypeal seta, carinae subparallel, converging or diverging, frontal margin overhanging mandibles, with or without a pair of clypeal teeth, clypeal margin may be rounded or deeply concave. Antennae 12-segmented or 10-segmented (Chelaner decuria) with a 3-segmented club. Palpal formula 2,3 or 2,2, mandibular tooth count 3–7. Eyes well developed, small to large, circular or oval.

Promesonotal suture not extending on to dorsal surface, rarely complete dorsally. Metanotal groove moderately to deeply impressed or very shallow. Propodeum rounded to slightly concave on the dorsal and posterior surfaces, which may be distinctly carinate or with barely raised, rounded ridges, propodeum less commonly dentate (variably so in Chelaner insolescens) or spinose (Chelaner sculpturatus and Chelaner sublamellatus). Metapleural gland and lobes well developed.

Petiole pedunculate, node large, quadrate and parallel-sided or more triangular with a rounded apex. Post-petiole node present, high and rounded with distinct anterior and posterior surfaces or, less commonly, low with a gently sloping anterior surface (Chelaner crinitus, Chelaner kiliani, Chelaner petiolatus, Chelaner tambourinensis).

Colour ranges from pale yellow to dark amber, red and black. Sculpture highly variable from smooth and glossy to punctures restricted to mesopleuron, to head, mesosoma and waist entirely punctate, reticulate or striate.

Species by Region
Number of species within biogeographic regions, along with the total number of species for each region.

Species Uncertain

 * Chelaner sp. ANIC-1:
 * Chelaner sp. ANIC-2:

Nomenclature

 *  CHELANER  [Myrmicinae: Solenopsidini]
 * Chelaner Emery, 1914f: 410 [as subgenus of Monomorium]. Type-species: Monomorium (Chelaner) forcipatum, by subsequent designation of Emery, 1922e: 168.

Taxonomic History

 * Chelaner in Myrmicinae, Solenopsidini: Forel, 1917: 242 [subtribe Monomoriini]; Emery, 1922e: 168; in Monomorium genus group: Ettershank, 1966: 81; in Monomoriini: Dlussky & Fedoseeva, 1988: 80.
 * Chelaner as subgenus of Monomorium: Emery, 1914f: 410; Emery, 1915i: 190; Forel, 1917: 242; Emery, 1922e: 168; Wheeler, W.M. 1922a: 676.
 * Chelaner senior synonym of Notomyrmex, Protholcomyrmex, Schizopelta: Ettershank, 1966: 93.
 * Chelaner (and its junior synonyms Notomyrmex, Protholcomyrmex, Schizopelta) as junior synonym of Monomorium: Bolton, 1987: 300; Heterick, 2001: 354.
 * Chelaner as genus: Ettershank, 1966: 93; Taylor & Brown, D.R. 1985: 55; Wheeler, G.C. & Wheeler, J. 1985: 257; Dlussky & Fedoseeva, 1988: 80 (anachronism); Sparks et al., 2019: 232.

Taxonomic Notes
Sparks et al. (2019): Ettershank (1966) refers to the propodeal spiracle opening into a vestibule as a character that separates species of Chelaner from Monomorium. The first author has examined a large number of Chelaner species and, although the propodeal spiracle is obviously vestibulate for several species, it is not evident for many of them. This is largely due to them having a very dark or heavily sclerotised cuticle that obscures anything below the surface. Similarly, for those species that remain in Monomorium, none were observed to have a vestibulate spiracle, but it is often difficult to see through the cuticle to determine whether it is vestibulate or not. Bolton (1987) reviewed the characters Ettershank (1966) had used to raise Chelaner to genus level, referring to the palpal formula and vestibulate nature of the spiracle as the only diagnostic characters separating Chelaner from Monomorium, while all the others occurred in both genera (these included the number of antennal segments, the structure of the clypeus and the pedunculate petiole). Further evidence that this character is not particularly useful is Ettershank’s (1966) observation that Monomorium rothsteini, a species that clearly belongs to the Monomorium clade, has a vestibulate propodeal spiracle.

Although the molecular data presented above support two distinct clades, the morphological diagnoses for these two genera remain problematic in that some specimens are difficult to identify, and a more thorough examination of their morphology that scrutinises additional characters will be required in future. In this respect, male genitalia and structure of the sting apparatus (see Kugler 1978) are likely character systems worth exploring.