Tetramorium validiusculum

Known from rainforest and disturbed forest habitats (pine and coffee). Collections have been made from rotten wood and under bark.

Identification
Bolton (1977) - This species is a sibling of Tetramorium pacificum, differentiated from it by the strongly reduced cephalic sculpture found in validiusculum. In some respects it resembles Tetramorium cynicum of the Philippines (see there), another sibling of pacificum whose range does not appear to overlap that of validiusculum, which is restricted to New Guinea and Queensland, particularly the Cape York Peninsula.

Distribution based on Regional Taxon Lists
Australasian Region: Australia. Indo-Australian Region: New Guinea.

Nomenclature

 *  validiusculum. Tetramorium pacificum subsp. validiusculum Emery, 1897c: 585 (w.) NEW GUINEA. Raised to species: Wilson & Taylor, 1967: 73. Senior synonym of longicarinum: Bolton, 1977: 104.
 * longicarinum. Tetramorium longicarinum Donisthorpe, 1941h: 57 (w.) NEW GUINEA. Junior synonym of validiusculum: Bolton, 1977: 104.

Worker
Bolton (1977) - TL 3.7-4.6, HL 0.86-1.16, HW 0.74-1.10, CI 84-94, SL 0.62-0.84, SI 76-87, PW 0.56-0.74, AL 1.02-1.30 (20 measured).

Mandibles unsculptured, smooth except for pits from which hairs arise. Anterior clypeal margin with a weakly developed median impression or notch. Median portion of clypeus with three main longitudinal carinae, in some large specimens the anterior half of the clypeus feebly transversely concave. Frontal carinae strongly developed, extending back almost to the occipital margin. Eyes with maximum diameter c. 0.18-0.23. Propodeal spines long, acute, usually narrow and sometimes slightly upcurved along their length. Metapleural lobes triangular, acute and feebly upcurved. Petiole node in profile shaped as in pacificum (see Fig. 15), with the anterior face shorter than the posterior so that the convex dorsal surface slopes upwards posteriorly and the posterodorsal angle is higher than the anterodorsal. The last cannot accurately be called an angle as in this species the anterior face joins the dorsum through a curve. Dorsum of head sculptured with a series of spaced longitudinal carinae or rugulae, some of which may be short or broken. Cross-meshes are either completely absent or a few cross-meshes or anastomoses may be present occipitally, but there is never a strongly developed rugoreticulum behind the level of the eyes as is found in most species of this group, nor do cross-meshes occur in front of the level of the posterior margins of the eyes. Ground sculpture faint and inconspicuous so that spaces between rugulae and carinae on head are shiny and mostly quite smooth. Dorsal alitrunk, petiole and postpetiole usually reticulate-rugose but this is commonly reduced in density and intensity. Gaster un sculptured, smooth and shining. All dorsal surfaces of head and alitrunk with numerous long, erect or suberect hairs. Colour uniform very dark brown to black.

Type Material
Bolton (1977) - Syntype workers, New Guinea: Berlinhafen (L. Biro) [examined].