Monomorium geminum

This is a cryptic species and is only separable from its sister species Monomorium topend using genetic analysis. Both species are commonly encountered in the tropical savannah region of northern Australia. Known specimens are limited to the Northern Territory but the distribution of both M. geminum and M. topend is likely to extend across the northern parts of Western Australia and Queensland where this habitat exists.

Identification
Sparks et al. (2015) - A member of the M. rothsteini species group. A large, amber orange species with a shallowly concave to sinuous clypeal anterodorsal margin, strigate frons, cuboid propodeum and very broad petiole node. This species cannot be separated from Monomorium topend based on morphology, but the two species are easily separated from all other species here by a very broad petiole node in combination with a shallowly concave to sinuous clypeus.

Distribution
This species is known from two populations in the far north of the Northern Territory.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Genetics
COI sequences. Genbank accession numbers for this species are KC572880–KC572882, KC572884 and KC573021.

Nomenclature

 *  geminum. Monomorium geminum Sparks, in Sparks, Andersen & Austin, 2015: 503, figs. 5a–c, 11c (w.) AUSTRALIA.

Worker
(n=9). HW 0.82–0.94, HL 0.86–0.98, EL 0.16–0.2, PMH 0.33–0.39, PH 0.33–0.41, PNH 0.21–0.27, LHW 0.49–0.57, EW 0.10–0.12, PML 0.59–0.68, ML 0.99–1.13, PL 0.29–0.37, PNWdv 0.27–0.35.

Large species with a medium sized, rectangular head; posterior cephalic margin straight to shallowly concave. Anterodorsal margin of the clypeus shallowly concave or sinuous with frontolateral carinae present as raised ridges that do not extend anteriorly beyond anteroventral clypeal margin; anteroventral margin without a small median projection, margin appears straight. Frons strigate, strigae extending well above antennal lobes; coarse lateral cephalic strigae reach anterior eye margin. Eyes small, EW < 0.2 x LHW, 11 ommatidia in longest vertical axis, 10 in longest horizontal axis. Antennal scapes with paired erect hairs dorsally that are approximately twice as long as those on ventral surface.

Mesonotum rugulose/strigate on lateral curvature and in metanotal groove, smooth medially; promesonotal suture present in many specimens as a faint punctate line; posterior mesonotum with faint strigulae or smooth, appears raised with a horseshoe shaped margin in many specimens or may be flat and contiguous with surrounding surface. Mesopleuron alveolate with a few strigae extending anteriorly from metanotal groove. Propodeum in lateral view with dorsolateral angles almost forming a right angle; posterior margin appears vertical, propodeum appears cuboid; laterally alveolate with strigae extending over metapleural gland bulla and curving from dorsal half of metanotal groove onto dorsal surface and in posterodorsal corner. Dorsal surface of propodeum with transverse anterior carina prominent, transverse strigae present, longitudinal carinae present, converging anteriorly, most specimens with obvious concavity between dorsolateral corners. Petiole node broad, more than 2.5x eye width when viewed from above; shape in posterior view tapering from broad midline to rounded apex; in lateral view anterior and posterior faces sub parallel, apex broadly rounded from higher anterior face to lower posterior face. Petiole node and postpetiole finely reticulate, sculpture not extending on to dorsal surface. T1 finely reticulate, sculpture covering at least anterior half of surface.

Head and mesosoma light to dark amber orange, legs orange brown, petiole and postpetiole infuscated on dorsal half, metasoma predominantly dark brown on tergites, sternites orange, some specimens with T1 infused with orange at the juncture with the postpetiole. Hairs over entire body appear dull yellow.

Type Material
Holotype worker. Northern Territory, Surprise Creek, Litchfield NP, 1 Aug 2010, A. Andersen ANA10–22 (deposited in NTM). Paratypes. Northern Territory, 1 workers, same data as holotype, 5 workers, same data as holotype, ANA10–23, 1 workers, same data as holotype, ANA10–24, 7 workers, same data as holotype, ANA10–26; 20 workers, Mary R. Station, Kakadu NP, 24 Jul 2008, A. Andersen, TERC66 (deposited in NTM,, , WAM).

Etymology
The specific name is taken from the Latin word for twin and refers to the close morphological affinities with the species Monomorium topend.

References based on Global Ant Biodiversity Informatics

 * Sparks K. S., A. N. Andersen, and A. D. Austin. 2014. Systematics of the Monomorium rothsteini Forel species complex (Hymenoptera: Formicidae), a problematic ant group in Australia. Zootaxa 3893(4): 489-529.