Tetramorium orientale

This species is only known from the type locality, which is given as "Imerina". This place name today applies to a large area on the Central Plateau of Madagascar so it is difficult to determine with any accuracy where the types were found.

Identification
A member of the Tetramorium bessonii-species group

Tetramorium orientale is easily recognisable within its species group due to the character combination of: well-developed, conspicuous promesonotal suture; high nodiform petiolar node in profile with approximately parallel anterior and posterior faces, anterodorsal and posterodorsal angles at about same height, dorsum not tapering backwards posteriorly; absence of standing hairs on waist segments and first gastral tergite, and very short, appressed pubescence on first gastral tergite. (Hita Garcia and Fisher 2012)

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  orientale. Tetramorium (Xiphomyrmex) bessonii var. orientale Forel, 1895c: 247 (w.) MADAGASCAR. Junior synonym of bessonii: Bolton, 1979: 141. Revived from synonymy and raised to species: Hita Garcia & Fisher, 2012: 22.

Worker
Hita Garcia and Fisher (2012) - HL 0.82; HW 0.84; SL 0.62; EL 0.18; PH 0.48; PW 0.63; WL 1.06; PSL 0.28; PTL 0.19; PTH 0.34; PTW 0.30; PPL 0.25; PPH 0.35; PPW 0.39; CI 102; SI 74; OI 21; DMI 59; LMI 45; PSLI 34; PeNI 47; LPeI 57; DPeI 155; PpNI 62; LPpI 71; DPpI 156; PPI 132 (one measured).

Head wider than long (CI 102). Anterior clypeal margin with distinct median impression. Frontal carinae well developed, ending shortly between posterior eye margin and posterior head margin. Antennal scrobes faint to absent, posterior and ventral margins not differentiated. Antennal scapes short, not reaching posterior head margin (SI 74). Eyes small to moderate (OI 21). Mesosomal outline in profile convex, dorsally transversely rounded, weakly marginate from lateral to dorsal mesosoma, promesonotal suture present, metanotal groove weakly developed; mesosoma comparatively stout and high (LMI 45). Propodeal spines long, spinose, and acute (PSLI 34). Propodeal lobes very small and broadly triangular. Petiolar node high nodiform, anterior and posterior faces approximately parallel, anterodorsal and posterodorsal angles at about same height, dorsum not tapering backwards posteriorly; node in dorsal view not strongly transverse, approximately 1.5 to 1.6 times wider than long (DPeI 155), in lateral view 1.8 times higher than long (LPeI 57). Postpetiole in profile rounded and weakly anteroposteriorly compressed, 1.4 times higher than long (LPpI 71), in dorsal view approximately approximately 1.5 to 1.6 times wider than long (DPpI 156). Postpetiole in profile approximately as voluminous as petiolar node, in dorsal view 1.3 times wider than petiolar node (PPI 132). Mandibles striate; clypeus with strong median longitudinal rugae and one weaker ruga at each side; cephalic dorsum between frontal carinae with one well-developed longitudinal median ruga and traces of short rugulae laterally, median ruga of same length as frontal carinae and diverging approximately at eye level into two rugae running to posterior clypeal margin; scrobal area unsculptured, lateral and ventral head anteriorly with irregular longitudinal rugulae, posteriorly with almost unsculptured; ground sculpture on head faint to absent. Mesosoma, waist segments, and gaster unsculptured, smooth, and shining. Head with several pairs of standing hairs, mesosoma with only one pair on pronotal dorsum, waist segments and first gastral tergite without any pilosity; all dorsal surfaces of body with widely-spaced, very short, and appressed pubescence. Body uniformly brown.

Type Material
Holotype worker, MADAGASCAR, Fianarantsoa, Imerina (Sikora) (MHNG: CASENT0101744) [examined]. (Hita Garcia and Fisher 2012)

References based on Global Ant Biodiversity Informatics

 * Forel A. 1895. Nouvelles fourmis de l'Imerina oriental (Moramanga etc.). Annales de la Société Entomologique de Belgique 39: 243-251.
 * Garcia H. F. and B. L. Fisher. 2012. The ant genus Tetramorium Mayr (Hymenoptera: Formicidae) in the Malagasy regiontaxonomy of the T. bessonii, T. bonibony, T. dysalum, T. marginatum, T. tsingy, and T. weitzeckeri species groups. Zootaxa 3365: 1-123
 * Wheeler W. M. 1922. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. IX. A synonymic list of the ants of the Malagasy region. Bulletin of the American Museum of Natural History 45: 1005-1055