Meranoplus ajax

This is a widespread species covering most of the arid to monsoonal areas of Australia, absent in the southernmost parts.

Identification
Schödl (2007) - M. ajax not only is one of the more widely distributed taxa, it is by far also one of the most variable species within the diversus-group. However, certain trends within the variability are displayed by different populations: Southern and central Australian samples show a distinct gastral striation and long thin whitish pilosity, whereas the striation vanishes and is reduced to almost entirely absent in northern populations, where the pilosity is shorter and stouter. In addition, the shape of the clypeal prominence varies markedly as does the petiolar shape and the outline of the promesonotal shield. Since transition between these populations seems to occur, I here refrain from describing new taxa. Genetic information may help to elucidate whether there are well defined subspecies or there is even more than one species hidden in this taxon. However, despite the high degree of variability, M. ajax as here defined is easily separated from others by the clypeal prominence.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  ajax. Meranoplus mars r. ajax Forel, 1915b: 44 (w.) AUSTRALIA. Raised to species: Taylor, 1990c: 34. See also: Schödl, 2007: 376.

Worker
Schödl (2007) - (n = 43). TL 6.50-9.25, HL 1.65-2.40, HW 1.70-2.60, FC 1.38-1.95, CI 100-117, CS 1.68-2.50, SL 0.89-1.20, SI1 43-52, SI2 45-53, PML 1.07-1.58, PW 1.38-2.05, PMD 1.35-2.08, PMI2 91-104, ML 1.50-2.0, PSL 0.53-0.84, PTLL 0.50-0.70, PTLH 0.63-0.90, PTI 72-82, PTDW 0.63-0.90, PPLL 0.43-0.58, PPLH 0.58-0.93, PPI 59-78, PPDW 0.68-0.95, PT/PP 80-100.

Mandible with three teeth. Clypeus in full face view longitudinally carinulate, with conspicuous somewhat tricuspidate anteriorly projecting elaboration, consisting of strong medial carina and lateral carinae, that merge into lateral angulate to rounded lobes, anterior projections occasionally reduced. Head distinctly wider than long, lateral sides almost straight, feebly narrowing anteriorly, preoccipital corners bulbously rounded, rear margin emarginate. Frontal carinae markedly narrower than head (FI 124 - 143), sinuately and evenly narrowed from about middle of length of head towards clypeus, anterolaterally extended into narrowly rounded projections which together with clypeus distinctly overhang mandibular section. Antennal scrobe in lateral view reaching middle of length of head. Distinctly transversely carinulate at rear, occasionally with additional shagreening. Genae and ventrolateral sides of head carinate to rugose, preoccipital lobes reticulate. Compound eyes relatively small (REL 0.15-0.19, EL 0.31-0.41, with 15-21 ommatidia in the longest row), situated distinctly in front of middle of lateral sides of head, dorsal ocular margin never reaching ventral scrobal margin.

Promesonotum wider than long (PMI 120-140), concealing lateral sides of mesosoma only anteriorly. Propodeal declivity and propodeal spines visible from above; lateral sides of promesonotum occasionally translucently margined, anterolateral corners rectangular, at most with stout anterolaterally projecting teeth; promesonotal suture absent or occasionally seen as faint transverse line; at its level laterally with deep excision on each side of the shield; posteriorly to excision with acute posteriorly directed lateral projection; posterolateral and posterior mesonotal projections reduced to triangular stout teeth. Propodeal spines long and slender, in dorsal view markedly diverging and slightly curved, emerging distinctly above middle of propodeal length.

Petiole in profile broadly triangular, sometimes obliquely truncated, anterior face straight and delicately rugulose, posterior face distinctly rugose. Dorsal postpetiole nodiform, tapering towards base, occasionally wedge-shaped, with ventral medium sized tooth, rugose throughout.

First gastral tergite conspicuously striate to mictroreticulate. Dorsum of head longitudinally costulate, additionally with few transverse meshes, at rear reticulate, with microsculpture which varies from nothing to a dense reticulum. Promesonotal shield irregularly to very regularly rugose or rugoreticulate. Pilosity consisting of short and longer hairs reaching to 600 μm.

Concolorous brown to dark-brown, frequently with the gaster somewhat brighter.

References based on Global Ant Biodiversity Informatics

 * Andersen A. N., J. Lanoue, and I. Radford. 2010. The ant fauna of the remote Mitchell Falls area of tropical north-western Australia: Biogeography, environmental relationships and conservation significance. Journal of Insect Conservation 14: 647-661.
 * Schödl S. 2007. Revision of Australian Meranoplus: the Meranoplus diversus group. Memoirs of the American Entomological Institute 80: 370-424.
 * Taylor R. W. 1987. A checklist of the ants of Australia, New Caledonia and New Zealand (Hymenoptera: Formicidae). CSIRO (Commonwealth Scientific and Industrial Research Organization) Division of Entomology Report 41: 1-92.