Monomorium sydneyense

Possibly the most abundant ant in Australia.  Monomorium sydneyense can be found in virtually all Australian habitats. (Heterick 2009)

Identification
Heterick (2009) - The appearance of workers of what is currently known as M. sydneyense varies enormously, from uniformly dark chocolate with a shagreenate exoskeleton, through orange-and-brown to light yellow with a smooth, shiny appearance, along with many specimens of intermediate facies. The propodeum (and often, the promesonotum and mesopleuron) can be long and reticulate-punctate or shorter and relatively unsculptured. A minute, small-eyed pale form with a darker head is most common in the .SWBP. In workers of coastal populations of this form the clypeal carinae are often extended beyond the clypeus as small spines, and the antennal count in at least some populations is 10. Since workers of these ants are all but morphologically indistinguishable from other workers with the normal count of 11 segments, molecular techniques are probably necessary to determine whether these populations represent a separate species. What appears to be a similar form with the same number of antennal segments has been identified in the Monarto region of South Australia. However, workers of the latter are darker in colour without extended clypeal carinae.

Distribution based on Regional Taxon Lists
Australasian Region: Australia, New Zealand.

Nomenclature

 *  sydneyense. Monomorium sydneyense Forel, 1902h: 442 (w.) AUSTRALIA. Heterick, 2001: 416 (q.m.). Combination in M. (Mitara): Emery, 1914b: 184; in M. (Lampromyrmex): Emery, 1922e: 184. Senior synonym of barretti, nigella; Heterick, 2001: 415.
 * nigella. Monomorium (Mitara) sydneyense subsp. nigella Emery, 1914b: 184, fig. 3 (w.) AUSTRALIA. Viehmeyer, 1925a: 28 (q.). Combination in M. (Lampromyrmex): Emery, 1922e: 184. Junior synonym of sydneyense: Heterick, 2001: 415.
 * barretti. Monomorium (Lampromyrmex) fraterculus var. barretti Santschi, 1928e: 467 (w.) AUSTRALIA. Subspecies of fraterculum: Taylor & Brown, D.R. 1985: 70. Junior synonym of sydneyense: Heterick, 2001: 415.