Tetramorium nipponense

Known from rainforest and disturbed forests (rubber plantation, botanical garden), with sampling from low vegetation and litter samples.

Identification
Bolton (1977) - T. nipponense overlaps the range of the related Tetramorium bicarinatum in the northern parts of the IndoAustralian and Oriental regions. The two are separated by the respective lengths of the long hairs arising from the frontal carinae, which are longer than the maximum diameter of the eye in nipponense, shorter in bicarinatum. Also, the gaster in bicarinatum is always conspicuously darker in colour than the head and alitrunk whilst in nipponense the entire ant tends to be unicolorous, with only slight variation in gastral colour. Finally, the petiole node in bicarinatum tends to have the anterior and posterior faces about equal in length in profile so that the antero- and posterodorsal angles are approximately on a level, whereas in nipponense the posterior face is somewhat higher than the anterior so that the angles are not on the same level, the posterodorsal being higher. This node form is also encountered in Tetramorium insolens, which overlaps the eastern end of the range of nipponense, but in insolens the mandibles are not striated. Finally, the closely related Tetramorium indicum is best separated by the characters noted in the key.

Distribution based on Regional Taxon Lists
Oriental Region: Thailand, Vietnam. Palaearctic Region: China, Japan.

Nomenclature

 *  nipponense. Tetramorium guineense subsp. nipponense Wheeler, W.M. 1928d: 115 (w.) JAPAN. Raised to species: Bolton, 1977: 100.

Worker
TL 3.3-3.7, HL 0.72-0.88, HW 0.62-0.78, CI 84-90, SL 0.54-0.64, SI 80-88, PW 0.48-0.58, AL 0.86-1.04 (20 measured).

Mandibles finely and densely longitudinally striate. Anterior clypeal margin with a distinct median notch or impression; median portion of clypeus with three strong longitudinal carinae. Frontal carinae strong, reaching back almost to the occipital margin. Eyes moderate, maximum diameter c. 0.18-0.20, about 0.25-0.28 x HW. Pronotal corners in dorsal view angulate. Propodeal spines in profile elongate and narrow, either upcurved along their whole length or abruptly and strongly upcurved at their apices, or both. Metapleural lobes elongate-triangular, narrow, acute and somewhat upcurved, or with their apical portions more or less spiniform. Petiole node in profile with the anterior face shorter than the posterior so that the dorsal surface slopes slightly upwards posteriorly and the posterodorsal angle is on a higher level than the anterodorsal. Dorsum of head with a loose rugoreticulum, cross-meshes occurring as far forwards as the level of the anterior margins of the eyes or in some cases approaching the posterior border of the clypeus. Dorsal alitrunk and dorsum and sides of pedicel segments reticulate-rugose, but in some specimens sculpture of postpetiole dorsum is predominantly or entirely longitudinal. Base of the first gastral tergite usually with vestiges of costulae, absent in some specimens, otherwise gaster unsculptured. Numerous long, erect or suberect hairs present on all dorsal surfaces of head and body, the longest of those projecting from the dorsum of the frontal carinae longer than the maximum diameter of the eye. Colour uniform yellowish brown, rarely with the gaster very slightly lighter or darker than the alitrunk.

Type Material
Syntype workers, Japan: Nagasaki, Michino-o, 3.vi.25 (F. Silvestri)  [examined].