Tetramorium aherni

Tetramorium aherni is known from Befingotra, Marojejy, and Makirovana in the north-eastern part of Madagascar, but also from Ambalagoavy, which is situated much further south in eastern Madagascar. The species is only found in lowland or montane rainforests ranging from 450 to 900 m elevation, and seems to prefer the leaf litter stratum. (Hita Garcia and Fisher 2012)

Identification
Tetramorium aherni is easily distinguishable within the species group due to the following character combination: eyes moderate to large (OI 22- 24); propodeal spines very long (PSLI 41 - 45); petiolar node with anterodorsal and posterodorsal margins at about the same height, dorsum flat to weakly convex. (Hita Garcia and Fisher 2012)

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  aherni. Tetramorium aherni Hita Garcia & Fisher, 2012: 56, figs. 34, 36, 37, 111-113, 142 (w.) MADAGASCAR.

Worker
HL 0.91 - 0.98 (0.93); HW 0.82 - 0.89 (0.84); SL 0.67 - 0.74 (0.71); EL 0.19 - 0.21 (0.20); PH 0.44 - 0.52 (0.46); PW 0.62 - 0.69 (0.64); WL 1.11 - 1.21 (1.15); PSL 0.37 - 0.42 (0.40); PTL 0.30 - 0.35 (0.32); PTH 0.34 - 0.38 (0.36); PTW 0.27 - 0.31 (0.28); PPL 0.31 - 0.34 (0.32); PPH 0.37 - 0.40 (0.38); PPW 0.34 - 0.39 (0.36); CI 90 - 92 (90); SI 81 - 86 (84); OI 22 - 24 (23); DMI 54 - 57 (56); LMI 39 - 43 (40); PSLI 41 - 45 (43); PeNI 42 - 46 (44); LPeI 84 - 93 (89); DPeI 86 - 94 (89); PpNI 53 - 60 (56); LPpI 82 - 87 (84); DPpI 106 - 117 (113); PPI 121 - 133 (128) (twelve measured).

Head distinctly longer than wide (CI 90 - 92); posterior head margin concave. Anterior clypeal margin medially impressed. Frontal carinae strongly developed, diverging posteriorly, and ending at corners of posterior head margin. Antennal scrobes developed, moderately deep and broad but without defined ventral margins. Antennal scapes of moderate length, not reaching posterior head margin (SI 81 - 86). Eyes small to moderate (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 high (LMI 39 - 43). Propodeal spines very long, spinose, and acute (PSLI 41 - 45); propodeal lobes well-developed, triangular to elongate-triangular, and acute. Petiolar node in profile rectangular nodiform, approximately 1.1 to 1.2 times higher than long (LPeI 84 - 93), anterior and posterior faces approximately parallel, anterodorsal and posterodorsal margins situated at about same height, dorsum flat to weakly convex; node in dorsal view approximately 1.1 times longer than wide (DPeI 86 - 94). Postpetiole in profile subglobular, approximately 1.1 to 1.2 times higher than long (LPpI 82 - 87); in dorsal view around 1.1 to 1.2 times wider than long (DPpI 106 - 117). Postpetiole in profile higher than petiolar node and generally appearing slightly more voluminous, in dorsal view approximately 1.2 to 1.3 times wider than petiolar node (PPI 121 - 133). Mandibles longitudinally rugose/rugulose, sometimes weakly so, sometimes partly sculptured and partly unsculptured; clypeus longitudinally rugose, with three to eight rugae, median ruga always present, remaining rugae variably developed; cephalic dorsum between frontal carinae with 8 to 11 longitudinal rugae, most rugae running unbroken from posterior head margin to anterior clypeus, few rugae interrupted and none with cross-meshes; scrobal area mostly unsculptured; lateral and ventral head longitudinally rugose with very few cross-meshes. Mesosoma laterally and dorsally distinctly longitudinally rugose. Forecoxae unsculptured, smooth, and shining with very weak, superficial ground sculpture (punctate or rugulose). Waist segments strongly longitudinally rugose, more irregular dorsally than laterally. Base of first gastral tergite distinctly costulate, remainder of gaster unsculptured, smooth and shining. Ground sculpture generally faint to absent everywhere on body. All dorsal surfaces of head, mesosoma, waist segments, and gaster with abundant, long, and fine standing hairs. Anterior edges of antennal scapes with suberect to erect hairs. Body of uniform dark brown to black colour.

Type Material
Holotype worker, MADAGASCAR, Antsiranana, Parc National de Marojejy, Manantenina River, 27.6 km 35° NE Andapa, 9.6 km 327° NNW Manantenina, 14.435 S, 49.76 E, 775 m, rainforest, sifted litter (leaf mold, rotten wood), collection code BLF08872, 15.-18.XI.2003 (B.L. Fisher et al.) (: CASENT0045755). Paratypes, 15 workers with same data as holotype (: CASENT0045607; CASC: CASENT0045595; CASENT0045603; CASENT0045675; CASENT0045679; CASENT0045687; CASENT0045696; CASENT0045750; CASENT0045766; CASENT0045771; CASENT0045774; CASENT0045779; : CASENT0045599; : CASENT0045761; : CASENT0045746).

Etymology
The new species is dedicated to Dan Ahern for his contribution to the Madagascar Project.