Tetramorium marginatum

This species seems to prefer montane rainforest habitats, but can be also found in lowland rainforests, making its elevation range from 30 to 1300 m. In terms of preferred microhabitat, T. marginatum appears primarily to be a leaf litter inhabitant, though it was occasionally sampled from lower vegetation. (Hita Garcia and Fisher 2012)

Identification
A member of the Tetramorium marginatum-species group / Key to Tetramorium marginatum-group species

The following character combination separates Tetramorium marginatum from the other members of the species group: head longer than wide to almost as long as wide (CI 94 - 99); petiolar node in profile triangular cuneiform and strongly anteroposteriorly compressed dorsally; mesosomal dorsum usually completely unsculptured, smooth and shining, very rarely few superficial traces of rugulae present on pronotum; long standing hairs on mesosoma comparatively few and generally restricted to dorsolateral margins of pronotum and mesonotum, sometimes one or two hairs present medially at border between mesonotum and propodeum; body colouration dark brown to black. (Hita Garcia and Fisher 2012)

Distribution
Tetramorium marginatum is distributed in eastern and northern Madagascar, although its range is somewhat disjunct. The southernmost known locality is Manombo and from there the species seems to be comparatively common through Vevembe, Ivohibe to Ranomafana. The next known region to the north, where it appears to be common, is from Andasibe, Ambatovy, and Torotorofotsy to Zahamena. Further north in eastern Madagascar it is only known from Marotandrano. Interestingly, T. marginatum also occurs in one locality at the northernmost tip of Madagascar, the Montagne d'Ambre. (Hita Garcia and Fisher 2012)

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  marginatum. Tetramorium (Xiphomyrmex) marginatum Forel, 1895h: 485 (w.) MADAGASCAR. See also: Bolton, 1979: 142; Hita Garcia & Fisher, 2012a: 96.

Worker
Hita Garcia and Fisher (2012) - HL 0.68 - 0.80 (0.73); HW 0.65 - 0.79 (0.71); SL 0.53 - 0.63 (0.58); EL 0.14 - 0.17 (0.15); PH 0.31 - 0.41 (0.36); PW 0.46 - 0.60 (0.54); WL 0.83 - 1.00 (0.90); PSL 0.26 - 0.36 (0.31); PTL 0.09 - 0.16 (0.12); PTH 0.29 - 0.36 (0.33); PTW 0.27 - 0.31 (0.28); PPL 0.20 - 0.25 (0.23); PPH 0.28 - 0.33 (0.31); PPW 0.28 - 0.35 (0.31); CI 94 - 99 (97); SI 80 - 84 (82); OI 21 - 22 (22); DMI 53 - 62 (59); LMI 37 - 41 (39); PSLI 38 - 46 (42); PeNI 50 - 59 (53); LPeI 29 - 47 (37); DPeI 189 - 300 (242); PpNI 53 - 61 (57); LPpI 71 - 77 (74); DPpI 128 - 142 (135); PPI 104 - 113 (109) (15 measured).

Head longer than wide to almost as long as wide (CI 94 - 99). Anterior clypeal margin medially impressed. Frontal carinae weakly to moderately developed, ending between posterior eye margin and posterior head margin, usually closer to posterior eye. Antennal scrobes absent. Antennal scapes of moderate length, not reaching posterior head margin (SI 80 - 84). Eyes comparatively small (OI 21 - 22). Mesosomal outline in profile strongly convex, and margination from lateral to dorsal mesosoma strongly developed; promesonotal suture and metanotal groove absent; mesosoma comparatively high, compact, and stout (LMI 37 - 41). Propodeal spines very long, spinose, and acute (PSLI 38 - 46); propodeal lobes inconspicuous, small and broadly triangular. Petiolar node in profile triangular cuneiform, strongly anteroposteriorly compressed dorsally, approximately 2.1 to 3.5 times higher than long (LPeI 29 - 47), anterior and posterior faces not parallel, anterodorsal margin situated higher than posterodorsal, dorsum tapering backwards posteriorly; node in dorsal view between 1.8 to 3 times wider than long (DPeI 189 - 300). Postpetiole in profile approximately rounded and weakly anteroposteriorly compressed, approximately 1.3 to 1.4 times higher than long (LPpI 71 - 77), in dorsal view approximately 1.2 to 1.4 times wider than long (DPpI 128 - 142). Postpetiole in profile appearing approximately the same volume as petiolar node, in dorsal view approximately as wide as petiolar node to weakly wider (PPI 104 - 113). Mandibles varying from almost unsculptured, smooth, and shining to finely striate, usually mostly unsculptured with few striate areas; clypeus with one distinct median ruga and one or two weaker rugae or rugulae laterally; cephalic dorsum between frontal carinae with four to eight longitudinal rugae or rugulae, median ruga present, usually shorter or approximately of same length as frontal carinae and diverging approximately at eye level into two rugae running to posterior clypeal margin, remaining rugae or rugulae generally of same length as frontal carinae, sometimes broken or shorter; lateral and ventral head anteriorly with reticulate-rugose to rugulose sculpture, posteriorly almost unsculptured; ground sculpture on head faint to absent. Mesosoma laterally mostly unsculptured, posteroventrally reticulate-rugose to rugulose; dorsal mesosoma usually completely unsculptured, smooth, and shiny, rarely with few superficial traces of rugulae on pronotum. Waist segments and gaster unsculptured, smooth, and shiny. All dorsal surfaces of body with comparatively scarce, long, erect pilosity, hairs on mesosomal dorsum usually restricted to lateral margins, sometimes one or two hairs present medially at border between mesonotum and propodeum. Body of uniform dark brown to black colour.

Type Material
Hita Garcia and Fisher (2012) - Syntype workers, MADAGASCAR, Central Madagascar (Sikora) (: CASENT0101287, CASENT0101288) [examined].