Tetramorium mahafaly

Tetramorium mahafaly is only known from a few localities around the Mahafaly Plateau, and seems to be restricted to this area in South-Western Madagascar. At present, it is the only member of the T. sericeiventre group endemic to Madagascar, and seems to prefer relatively arid spiny forest or thicket habitats. (Hita Garcia and Fisher 2011)

Identification
Tetramorium mahafaly can be clearly differentiated from the other species of the group by the following combination of characters: petiolar node rectangular nodiform, relatively square (LPeI 95 - 103; DPeI 89 - 98), in profile roughly as long as high and in dorsal view mostly only weakly longer than wide; antennal scapes and tibiae with moderately sized, appressed pilosity; generally hairy species, propodeum always with standing hairs. (Hita Garcia and Fisher 2011)

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  mahafaly. Tetramorium mahafaly Hita Garcia & Fisher, 2011: 31, fig. 19 (w.) MADAGASCAR.

The new species can be separated from the only other species in the T. sericeiventre group present in the Malagasy region without any difficulty. The two differ significantly in terms of pilosity, size, and morphometry. The most obvious difference is pilosity, since T. mahafaly is much hairier than Tetramorium sericeiventre. The latter possesses only very short, appressed pubescence on the antennal scapes and tibiae whereas the first shows distinct, longer pilosity which is also appressed. In T. sericeiventre pilosity on all dorsal surfaces is sparse and absent on the propodeal dorsum while the pilosity of T. mahafaly is relatively more abundant and standing hairs are present on the propodeal dorsum. Furthermore, T. mahafaly (HL 0.610 - 0.680; PW 0.400 - 0.475; WL 0.760 - 0.875) is distinctly much smaller in size than T. sericeiventre (HL 0.770 - 0.990; PW 0.460 - 0.630; WL 0.950 - 1.30). Generally, body size must be treated with caution as there is a substantial intraspecific size variation observable within the genus Tetramorium (Bolton, 1977, 1979, 1980; Hita Garcia et al., 2010b). Even though T. sericeiventre shows impressive size variation, it is always much larger than T. mahafaly. In addition, the shape of the petiolar node is more square in T. mahafaly than in T. sericeiventre since the node of the latter is always much longer than high and also longer than wide (LPeI 104 - 120; DPeI 68 - 81), whereas the node of T. mahafaly (LPeI 95 - 103; DPeI 89 - 98) is generally roughly as long as high and sometimes only weakly longer than wide. The proportions of the widths of both waist segments also are fairly different. The postpetiole of T. sericeiventre (PPI 128 - 143) is usually between 1.3 to 1.4 times wider than the petiole whereas the postpetiole of T. mahafaly is generally around 1.2 times wider than the petiole (PPI 115 - 124).

Worker
HL 0.610 - 0.680 (0.641); HW 0.545 - 0.610 (0.578); SL 0.580 - 0.655 (0.614); EL 0.110 - 0.135 (0.126); PW 0.400 - 0.475 (0.438); WL 0.760 - 0.875 (0.808); PSL 0.090 - 0.120 (0.110); PTL 0.190 - 0.220 (0.202); PTH 0.190 - 0.220 (0.206); PTW 0.170 - 0.205 (0.191); PPL 0.155 - 0.175 (0.165); PPH 0.200 - 0.225 (0.213); PPW 0.210 - 0.245 (0.229); CI 89 - 92 (90); SI 103 - 109 (106); OI 20 - 23 (22); PSLI 14 - 19 (17); PeNI 41 - 47 (44); LPeI 95 - 103 (98); DPeI 89 - 98 (94); PpNI 50 - 55 (52); LPpI 75 - 80 (78); DPpI 133 - 144 (139); PPI 115 - 124 (120) (20 measured).

Head distinctly longer than wide (CI 89 - 92). Anterior clypeal margin entire and convex, lateral clypeus characteristically modified, in full-face view distinctly raised in front of antennal condyle and projecting forward as a tooth or denticle. Frontal carinae absent. Antennal scrobes absent. Antennal scapes relatively long, distinctly surpassing posterior head margin (SI 103 - 109). Eyes relatively small (OI 20 - 23), with 11 to 13 ommatidia in longest row. Mesosomal profile weakly convex, metanotal groove absent. Propodeal spines elongate-triangular, relatively narrow and short (PSLI 14 - 19). Propodeal lobes elongate-triangular to triangular, usually blunt, and about equal in length to propodeal spines but generally more voluminous. Petiolar node rectangular nodiform, in profile anterior and posterior faces roughly parallel, dorsum weakly convex, antero- and posterodorsal angle at about same height, node roughly as long as high, more often weakly longer than high, rarely higher than long (LPeI 95 - 103), in dorsal view always weakly to distinctly longer than high (DPeI 89 - 98). Postpetiole in profile rounded, noticeably higher than long (LPpI 75 - 80), in dorsal view much wider than long (DPpI 133 - 144), and distinctly wider than petiolar node (PPI 115 - 124). Mandibles always sculptured, striate to longitudinally rugose. Clypeus with one well-developed longitudinal ruga and some weaker and more irregular rugae or rugulae laterally. Head laterally, ventrally, and posteriorly reticulate-rugose to rugose, cephalic dorsum more rugose; ground sculpture moderately reticulate-punctulate. Mesosoma and waist segments reticulate-rugose with reticulate-punctulate ground sculpturation. Head, mesosoma, and waist segments with granular appearance. First gastral tergite densely reticulate-punctulate at base, rarely extending more than half the length of tergite, rest of gaster completely unsculptured, smooth, and shiny. All dorsal surfaces of head, mesosoma, waist segments, and gaster with numerous long, standing hairs; antennal scapes and tibiae with appressed pilosity. Head, mesosoma, waist segments, and legs of reddish brown to brown colour contrasting with gaster of dark brown to black colour, postpetiole often darker as well, and almost of same dark colour as gaster.

Type Material
Holotype worker, MADAGASCAR, Prov. Toliara, Mahafaly Plateau, 6.2 km 74° ENE Tampolo, 24° 39' S, 43° 69' E, 80 m, BLF05780, 21.-25.II.2002 (B.L. Fisher et al.) (: CASENT0448984). Paratypes, 59 workers with same data as holotype (: CASENT0448977; CASC: CASENT0448972, CASENT0448973, CASENT0448974, CASENT0448976, CASENT0448978, CASENT0448979, CASENT0448980, CASENT0448981, CASENT0448982, CASENT0448985, CASENT0448986, CASENT0448989, CASENT0448990, CASENT0448991, CASENT0448992, CASENT0448993, CASENT0448994, CASENT0448995, CASENT0448996, CASENT0448997, CASENT0448998, CASENT0449000; MNHG: CASENT0448983).

References based on Global Ant Biodiversity Informatics

 * Hita Garcia F., and B. L. Fisher. 2011. The ant genus Tetramorium Mayr (Hymenoptera: Formicidae) in the Malagasy regionintroduction, definition of species groups, and revision of the T. bicarinatum, T. obesum, T. sericeiventre and T. tosii species groups. Zootaxa 3039: 1-72.
 * Hita García, F., and B. L. Fisher. "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 (2012): 1-123.