Tetramorium tosii

This large and noticeable species is relatively abundant and common in most rainforests of Eastern and Northern Madagascar. It seems to be primarily arboreal or sub-arboreal, although it was often sampled on the ground as well. (Hita Garcia and Fisher 2011)

Identification
A member of the Tetramorium tosii species group

Hita Garcia and Fisher (2011) - The extremely long propodeal spines (PSLI 42 - 49) and long antennal scapes (SI 97 - 104) make Tetramorium tosii easily recognisable within the species group.

Bolton (1979) pointed out that the combination of 12-segmented antennae and the unique eye shape isolate this species from all other Malagasy Tetramorium species. However, we treat this diagnosis with caution. Examination of several hundred specimens from all Eastern Madagascar showed that the eye shape of T. tosii is more variable than originally described by Bolton (1979). Around the type locality in the Antongil Bay most specimens showed the strongly protuberant eye shape described by Bolton, but this character becomes gradually weaker in northern localities and most other rainforests south of this bay until it is not differently developed compared to Tetramorium tantillum or other species. Another character that deserves some attention is the shape of the petiolar node. In general, it is clublike to elongate nodiform with the posterodorsal angle much higher than the anterodorsal, and a strongly convex dorsum that slopes upwards posteriorly. Nevertheless, in some smaller specimens the anterodorsal angle was better developed and the dorsum less convex, making this character close to the petiolar node shape of T. tantillum. Even though both shapes are still quite different, the similarities can be misleading, and the safest means to separate T. tosii from T. tantillum is to compare the lengths of the antennal scapes and propodeal spines.

An additional important variation observed in T. tosii is its colouration. Almost all of the examined material from most of the distribution range was coloured dark brown to black. However, in the northernmost locality of its known distribution, the Foret de Binara, all specimens were yellowish-orange to orange-brown. The locality is of particular interest since it is comparatively isolated from most other rainforests where T. tosii was collected. The examination of all available specimens from Foret de Binara, however, did not provide any diagnostic character able to separate this population from Tetramorium tosii, and differential colouration alone is not sufficient to justify this step.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  tosii. Tetramorium tosii Emery, 1899f: 284, fig. (w.) MADAGASCAR. See also: Bolton, 1979: 153; Hita Garcia & Fisher, 2011: 45.

Worker
Hita Garcia and Fisher (2011) - HL 0.900 - 1.150 (1.013); HW 0.770 - 1.030 (0.884); SL 0.770 - 1.020 (0.888); EL 0.160 - 0.215 (0.186); PW 0.610 - 0.810 (0.707); WL 1.150 - 1.571 (1.340); PSL 0.395 - 0.560 (0.465); PTL 0.345 - 0.440 (0.394); PTH 0.290 - 0.400 (0.352); PTW 0.290 - 0.380 (0.337); PPL 0.290 - 0.355 (0.332); PPH 0.305 - 0.410 (0.366); PPW 0.310 - 0.395 (0.355); CI 85 - 90 (87); SI 97 - 104 (101); OI 18 - 22 (21); PSLI 42 - 49 (46); PeNI 44 - 53 (48); LPeI 104 - 121 (112); DPeI 83 - 88 (86); PpNI 46 - 55 (50); LPpI 85 - 99 (91); DPpI 104 - 111 (106); PPI 101 - 109 (105) (20 measured).

Head distinctly longer than wide (CI 85 - 90). Anterior clypeal margin entire and convex. Frontal carinae well-developed, almost reaching posterior head margin. Antennal scrobes reduced and absent. Antennal scapes relatively long and surpassing posterior head margin (SI 97 - 104). Eyes relatively small to moderately sized (OI 18 - 22), with 12 - 16 ommatidia in longest row, often characteristically modified, projecting from each side as strongly protuberant semicircles. Mesosomal profile relatively flat and only very weakly convex, metanotal groove absent. Propodeal spines extremely long, spinose, and acute (PSLI 42 - 49). Propodeal lobes short, triangular, and blunt to acute. Node of petiole elongate nodiform or clublike with a very long and up-curved peduncle, in profile posterodorsal angle much higher than anterodorsal, dorsum strongly convex and sloping upwards posteriorly, node longer than high in lateral view (LPeI 104 - 121), in dorsal view node distinctly longer than high (DPeI 83 - 88). Postpetiole in profile rounded, higher than long (LPeI 104 - 121), in dorsal view weakly wider than long (DPpI 104 - 111), and weakly wider than petiolar node (PPI 101 - 109). Mandibles distinctly sculptured, generally striate or longitudinally rugose. Clypeus with 3 well-developed longitudinal rugae. Head ventrally, laterally, and posteriorly with reticulate-rugose sculpturation, cephalic dorsum between frontal carinae longitudinally rugose, usually with 5 to 6 longitudinal rugae, merging with reticulate-rugose sculpturation posteriorly shortly before posterior head margin; ground sculpturation on head weak and faint. Mesosoma laterally irregularly rugose to rugulose, dorsally sculpturation much weaker, partly with weak, irregular rugulae and partly unsculptured, without any ground sculpture. Waist segments weakly sculptured, petiole laterally with weak irregular rugulation and dorsally almost unsculptured, postpetiole with distinctly less sculpturation than petiole, with few weak irregular rugulae to almost unsculptured, smooth, and shiny. First gastral tergite completely unsculptured, smooth, and shiny. All dorsal surfaces of head, mesosoma, waist segments, and gaster with abundant, long, standing hairs; hairs on antennal scapes and tibiae appressed. Colouration in almost all examined material uniformly dark brown to blackish brown, except one series with conspicuous yellowish-orange to orange-brown colour from Foret de Binara.

Type Material
Hita Garcia and Fisher (2011) - Syntype workers, MADAGASCAR, Baie d' Antongil, (Mocquerys) [examined].