Tetramorium orc

This species is only known from the type locality, the Parc National de Marojejy, where it was collected at comparatively high elevations ranging from 1575 to 2000 m. Tetramorium orc is the only species of the group that was predominantly found in montane shrubland habitats, and only rarely from montane rainforest, whereas all other group members were almost always collected from forests in different elevations. In addition, T. orc seems to live in leaf litter. (Hita Garcia and Fisher 2012)

Identification
A member of the Tetramorium dysalum-species group

Tetramorium orc can be recognised within the T. dysalum group using to the following character set: very short antennal scapes (SI 68 - 69); propodeal spines/teeth comparatively short (PSLI 19 - 23); weakly cuneiform petiolar node shape with the anterodorsal angle situated higher than the posterodorsal, so that the dorsum tapers backwards posteriorly; mesosomal dorsum with distinct longitudinal rugae/rugulae; completely unsculptured waist segments; dark brown colouration. (Hita Garcia and Fisher 2012)

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  orc. Tetramorium orc Hita Garcia & Fisher, 2012: 73, figs. 74, 75, 107-109 (w.) MADAGASCAR.

Worker
HL 0.67 - 0.74 (0.70); HW 0.63 - 0.71 (0.66); SL 0.43 - 0.49 (0.45); EL 0.14 - 0.17 (0.16); PH 0.34 - 0.37 (0.35); PW 0.43 - 0.51 (0.47); WL 0.79 - 0.91 (0.84); PSL 0.13 - 0.17 (0.15); PTL 0.13 - 0.16 (0.14); PTH 0.25 - 0.29 (0.27); PTW 0.18 - 0.22 (0.20); PPL 0.18 - 0.21 (0.19); PPH 0.24 - 0.27 (0.25); PPW 0.26 - 0.29 (0.27); CI 93 - 96 (94); SI 68 - 69 (69); OI 22 - 24 (24); DMI 53 - 58 (56); LMI 40 - 42 (41); PSLI 19 - 23 (22); PeNI 39 - 45 (41); LPeI 46 - 58 (53); DPeI 130 - 146 (137); PpNI 55 - 61 (57); LPpI 72 - 82 (77); DPpI 137 - 144 (140); PPI 130 - 144 (139) (11 measured).

Head distinctly longer than wide (CI 93 - 96). Anterior clypeal margin with distinct median impression. Frontal carinae well-developed, after posterior eye margin distinctly weaker, ending between posterior eye margin and posterior head margin. Antennal scrobes faint, shallow, and narrow. Antennal scapes short, not reaching posterior head margin (SI 68 - 69). Eyes of moderate size (OI 22 - 24). Mesosomal outline in profile weakly convex, moderately marginate from lateral to dorsal mesosoma; promesonotal suture and metanotal groove absent; mesosoma comparatively stout and compact (LMI 40 - 42). Propodeum armed with short, elongate-triangular to spinose spines or teeth (PSLI 19 - 23). Propodeal lobes short, triangular, and acute, distinctly much shorter than propodeal spines. Petiolar node weakly cuneiform, approximately 1.7 to 2.2 times higher than long (LPeI 46 - 58), anterodorsal margin moderately developed and situated higher than posterodorsal, dorsum strongly tapering backwards posteriorly; node in dorsal view between 1.3 to 1.5 times longer than wide (DPeI 130 - 146). Postpetiole in profile rounded, approximately 1.2 to 1.4 times higher than long (LPpI 72 - 82), in dorsal view between 1.3 to 1.5 times wider than long (DPpI 137 - 144). Postpetiole in profile less voluminous than petiolar node, in dorsal view approximately 1.3 to 1.5 times wider than petiolar node (PPI 130 - 144). Mandibles always unsculptured, smooth and shiny; clypeus with five to eight fine, longitudinal rugulae, no distinct median ruga, median anterior area often without sculpture; cephalic dorsum between frontal carinae with eight to 12 longitudinal rugulae, most rugae running from anterior clypeal margin to posterior head margin, rarely broken or with cross-meshes; scrobal area mostly unsculptured, remainder of lateral and ventral head with more irregular longitudinal rugulae. Ground sculpture reticulate-punctate, usually moderately developed, sometimes faint. Mesosoma laterally generally with irregular longitudinal rugulae, sometimes lateral pronotum almost unsculptured; mesosomal dorsum with longitudinal rugulae. Waist segments and gaster always unsculptured, smooth, and shining. All dorsal surfaces of body with long, erect pilosity. Whole body dark to very dark brown, often mesosoma of lighter, reddish brown colour.

Type Material
Holotype worker, MADAGASCAR, Antsiranana, Parc National de Marojejy, 25.4 km 30° NNE Andapa, 10.9 km 311° NW Manantenina, 14.445 S, 49.735 E, 2000 m, montane shrubland, ex soil, collection code BLF09377, 24.XI.2003 (B.L. Fisher et al.) (: CASENT0487093). Paratypes, nine workers with same data as holotype (CASC: CASENT0487090; CASENT0487091; CASENT0487092); 24 workers with same data as holotype except collection code BLF09376 and BLF09379 (: CASENT0487022; CASC: CASENT0487094; CASENT0487096; CASENT0487166; CASENT0487167; CASENT0487168; : CASENT0487023; : CASENT0487095); 26 workers with same data as holotype except collected from under stone or moss, or as ground foragers, and collection codes BLF09385, BLF09390, and BLF09392 (CASC: CASENT0487080; CASENT0487081; CASENT0487082; CASENT0487189; CASENT0487190; CASENT0487191; CASENT0487203; CASENT0487204; CASENT0487205).

Etymology
The name "orc" is derived from Old English and means "demon". The species epithet is a noun in apposition and thus invariant.

References based on Global Ant Biodiversity Informatics

 * 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