Known from mesic forest habitats where it has been found in litter samples.
Bolton (1977) - This is the most widespread species of the group, occurring in the Bismarck Archipelago and in Queensland (where a closely related species, Tetramorium australe, is also present) as well as being relatively common in parts of New Guinea. The closest relative of ornatum in New Guinea is the somewhat larger Tetramorium sculptatum, in which the frontal carinae are even more reduced and in which the antennal scrobes are completely lacking.
Keys including this Species
Distribution based on Regional Taxon Lists
Distribution based on AntMaps
Distribution based on AntWeb specimens
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The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.
- ornatum. Tetramorium ornatum Emery, 1897c: 585, pl. 15, fig. 27 (w.) NEW GUINEA. Senior synonym of obscurius: Bolton, 1977: 107.
- obscurius. Tetramorium ornatum var. obscurius Forel, 1901b: 11 (w.) NEW GUINEA (Bismarck Archipelago). Junior synonym of ornatum: Bolton, 1977: 107.
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
Bolton (1977) - TL 3.0-3.8, HL 0.70-0.92, HW 0.60-0.84, CI 84-91, SL 0.50-0.68, SI 80-87, PW 0.46-0.62, AL 0.86-1.14 (46 measured).
Mandibles striate, anterior clypeal margin convex and entire. Frontal carinae feeble, usually no more strongly developed than the longitudinal sculpture of the head, but extending back beyond the level of the eyes, sometimes almost reaching the occipital margin but here virtually indistinguishable from the other sculpture. Antennal scrobes present but exceedingly feeble. Maximum diameter of eye c. 0.12-0.16. Propodeal spines usually weakly downcurved along their length but sometimes almost straight or very weakly sinuate, variation being present in single nest-series. Metapleural lobes elongate-triangular and acute. Petiole in profile with a long peduncle and a long, low node, the dorsal length of which is about equal to or slightly greater than the height of the tergal portion. Clypeus with five distinct longitudinal carinae of about equal strength, sometimes with another intercalary pair present which are usually weaker or incomplete. Dorsum of head strongly sculptured with regular, more or less parallel longitudinal rugae or carinae, without cross-meshes. These rugae are closely packed, with usually 12-15 between the frontal carinae at the level of the eyes (a few specimens are known with 10-11). Dorsal alitrunk with a coarse rugoreticulum which extends down the sides of the pronotum. Sides of nodes of petiole and postpetiole rugose but on the postpetiole dorsum this is usually weaker. Gaster unsculptured. All dorsal surfaces of head and body with numerous fine hairs, those on the dorsal (outer) surface of the hind tibiae short and curved. Colour varying from reddish brown to blackish brown.
- Syntype, worker(s), Aitape (as Berlinhafen), Papua New Guinea, Musee d'Histoire Naturelle Genève.
- Bolton, B. 1977. The ant tribe Tetramoriini (Hymenoptera: Formicidae). The genus Tetramorium Mayr in the Oriental and Indo-Australian regions, and in Australia. Bulletin of the British Museum (Natural History). Entomology. 36:67-151. PDF (page 107, Senior synonym of obscurius)
- Emery, C. 1897c. Formicidarum species novae vel minus cognitae in collectione Musaei Nationalis Hungarici quas in Nova-Guinea, colonia germanica, collegit L. Biró. Természetr. Füz. 20: 571-599 PDF (page 585, pl. 15, fig. 27 worker described)