Tetramorium pleganon

Tetramorium pleganon possesses a comparatively wide distribution in Madagascar since it is found in many localities from Zombitse and Kalambatrita in the south up to Ambato and Antsahabe in the north. It appears to be comparatively flexible in its habitat preferences. Most of the localities where it was encountered consisted of rainforest, montane rainforest, or tropical dry forest, but the number of specimens collected in these habitats was comparatively low. In contrast, the largest number of examined specimens were sampled in Uapaca woodland, savannah grassland, and degraded forests, indicating that T. pleganon might be more successful in disturbed and open habitats than in dense forests. (Hita Garcia and Fisher 2012)

Identification
A member of the Tetramorium jedi species complex of the Tetramorium tortuosum-species group.

Tetramorium pleganon is easily recognisable within the T. tortuosum group in the Malagasy region due to the character combination of: propodeal spines long to very long (PSLI 37 - 44); petiolar node wider than long (DPeI 111 - 118); dorsum of petiolar node strongly rugose; first gastral tergite with superficial, fine, reticulate-punctate sculpture, ranging from basal third to more than half of tergite. Despite its wide distribution range and relative flexibility in habitat preference, T. pleganon is morphologically very stable throughout its range with very little variation in morphometry, shape, or colour. Despite its wide distribution range and relative flexibility in habitat preference, T. pleganon is morphologically very stable throughout its range with very little variation in morphometry, shape, or colour. (Hita Garcia and Fisher 2012)

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  pleganon. Tetramorium pleganon Bolton, 1979: 146 (w.) MADAGASCAR. See also: Hita Garcia & Fisher, 2012b: 53.

Worker
HL 0.87 - 1.05 (0.93); HW 0.85 - 1.02 (0.XX); SL 0.61 - 0.73 (0.66); EL 0.18 - 0.23 (0.19); PH 0.43 - 0.56 (0.48); PW 0.59 - 0.79 (0.69); WL 1.07 - 1.31 (1.17); PSL 0.32 - 0.43 (0.37); PTL 0.22 - 0.31 (0.25); PTH 0.34 - 0.44 (0.37); PTW 0.26 - 0.34 (0.29); PPL 0.27 - 0.34 (0.29); PPH 0.31 - 0.43 (0.35); PPW 0.34 - 0.43 (0.38); CI 96 - 99 (97); SI 71 - 74 (73); OI 20 - 23 (21); DMI 52 - 61 (59); LMI 38 - 43 (41); PSLI 37 - 44 (39); PeNI 40 - 44 (42); LPeI 63 - 73 (67); DPeI 111 - 118 (115); PpNI 52 - 61 (55); LPpI 80 - 89 (83); DPpI 122 - 137 (129); PPI 126 - 138 (130) (14 measured).

Head longer than wide (CI 96 - 99); posterior head margin moderately concave. Anterior clypeal margin medially impressed, often weakly so. Frontal carinae strongly developed, diverging posteriorly, and ending at corners of posterior head margin. Antennal scrobes developed, shallow to moderately deep, and broad, without defined posterior and ventral margins. Antennal scapes short, not reaching posterior head margin (SI 71 - 74). Eyes small to moderate in size (OI 20 - 23). 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 38 - 43). Propodeal spines very long, spinose and acute (PSLI 37 - 44); propodeal lobes short, triangular, and acute. Petiolar node in profile rectangular nodiform, approximately 1.1 to 1.2 times higher than long (LPeI 63 - 73), anterior and posterior faces approximately parallel, anterodorsal margin situated higher than posterodorsal, dorsum weakly tapering backwards posteriorly; node in dorsal view approximately 1.1 to 1.2 times wider than long (DPeI 111 - 118). Postpetiole in profile rounded, approximately 1.1 to 1.3 times higher than long (LPpI 80 - 89); in dorsal view around 1.2 to 1.4 times wider than long (DPpI 122 - 137). Postpetiole in profile approximately as voluminous as petiolar node, in dorsal view 1.2 to 1.4 times wider than petiolar node (PPI 126 - 138). Mandibles generally finely to strongly striate; clypeus longitudinally rugose, with four to nine rugae, median ruga always present and distinct, remaining rugae variably developed, usually weaker; cephalic dorsum between frontal carinae with 11 to 14 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, very rarely with cross-meshes. Ground sculpture on head generally feeble. Mesosoma laterally and dorsally distinctly longitudinally rugose, lateral mesosoma sometimes weaker sculptured than dorsum. Forecoxae generally unsculptured, smooth, and shining, sometimes with superficial sculpture. Ground sculpture on mesosoma generally faint to absent. Waist segments strongly rugose dorsally, laterally rugose sculpture much weaker; both waist segments with very conspicuous reticulate-punctate ground sculpture. First gastral tergite with fine, dense, reticulate-punctate ground sculpture, ranging from basal third to more than half of tergite. All dorsal surfaces of body with abundant, long, and fine standing hairs; first gastral tergite with mix of moderately long appressed to decumbent hairs and more abundant and longer suberect to erect hairs. Anterior edges of antennal scapes with decumbent to suberect hairs. Body a uniform very dark brown to black colour, appendages often lighter in colour.

Type Material
Hita Garcia and Fisher (2012) - Holotype worker, MADAGASCAR, Antsiranana, 84 km SW Sambava on road to Andapa, 70 - 160 m, degraded forest, strays on path, AB 43, 17.II.1977 (W.L. & D.E. Brown) (: CASENT0280587) [examined]. Paratypes, three workers with same data as holotype (: CASENT0102399; MCZ: CASENT0280588) [examined].

References based on Global Ant Biodiversity Informatics

 * Fisher B. L. 1997. Biogeography and ecology of the ant fauna of Madagascar (Hymenoptera: Formicidae). Journal of Natural History 31: 269-302.
 * Fisher B. L. 2003. Formicidae, ants. Pp. 811-819 in: Goodman, S. M.; Benstead, J. P. (eds.) 2003. The natural history of Madagascar. Chicago: University of Chicago Press, xxi + 1709 pp.
 * Hita Garcia F., and B. L. Fisher. 2012. The ant genus Tetramorium Mayr (Hymenoptera: Formicidae) in the Malagasy regiontaxonomic revision of the T. kelleri and T. tortuosum species groups. Zootaxa 3592: 1-85.