Tetramorium tabarum

Most specimens of T. tabarum have been collected from vegetation.

Identification
A member of the Tetramorium capillosum species complex, which is part of the Tetramorium tortuosum species group.

Key to the Tetramorium capillosum species complex

Hita Garcia and Fisher (2013) - Tetramorium tabarum is easily recognisable within the Afrotropical T. tortuosum group by the following character combination: antennal scape moderately long (SI 84 - 86); eyes large (OI 27 - 31); petiolar node nodiform with anterodorsal and posterodorsal margins relatively rounded, posterodorsal margin situated higher than anterodorsal margin, dorsum convex; mandibles unsculptured, smooth, and shining; petiole with very weak sculpture and postpetiole completely unsculptured; head, mesosoma, waist segments yellowish to bright orange, gaster very dark brown to black.

T. tabarum differs significantly from Tetramorium capillosum in eye size (OI 27 - 31 vs. OI 24 - 25), propodeal spine length (PSLI 22 - 25 vs. PSLI 31 - 43), and sculpture on mandibles and postpetiole, which is present and conspicuous in T. capillosum while absent in T. tabarum. The latter is also much smaller (WL 0.75 - 0.82) and bicoloured with a dark brown to black gaster contrasting with the remaining yellowish to orange body, which contrasts with the larger size (WL 1.02 - 1.19) and the uniformly very dark brown to black colouration of T. capillosum. Despite being often also bicoloured and within the same morphometric range, Tetramorium hecate is unlikely to be confused with T. tabarum. The antennal scapes are significantly longer in T. tabarum (SI 84 - 86) than in T. hecate (SI 73 - 77). More importantly, the petiolar node of T. tabarum has relatively rounded anterodorsal and posterodorsal margins with the posterodorsal margin situated higher than the anterodorsal, and the dorsum is convex, whereas in T. hecate the anterodorsal and posterodorsal margins are sharply defined and at about the same height. The varying development of the antennal scrobes is another difference. Tetramorium hecate possesses very well-developed scrobes with margins all around while the scrobes of T. tabarum are shallow without clear posterior and ventral margins.

The limited number of specimens of this species suggest intraspecific variation is very low.

Distribution
Tetramorium tabarum is known to occur in northern Gabon, western Cameroon close to the Gulf of Guinea, the southwest of the Central African Republic, and from the type locality in the northeast of the Democratic Republic of Congo. Its distribution seems even more disjunctive than that of T. capillosum, but is very likely due to a sampling artifact as already noted above for the latter species. We are very confident that more material of T. tabarum will be sampled in the area between the known localities.

Distribution based on Regional Taxon Lists
Afrotropical Region: Central African Republic, Democratic Republic of Congo.

Nomenclature

 *  tabarum. Tetramorium tabarum Bolton, 1980: 236, fig. 14 (w.) DEMOCRATIC REPUBLIC OF CONGO.

Worker
Hita Garcia and Fisher (2013) - measurements (N=10) HL 0.61 - 0.66 (0.63); HW 0.55 - 0.60 (0.57); SL 0.47 - 0.52 (0.49); EL 0.16 - 0.18 (0.17); PH 0.30 - 0.34 (0.32); PW 0.43 - 0.46 (0.44); WL 0.75 - 0.82 (0.79); PSL 0.14 - 0.16 (0.15); PTL 0.20 - 0.22 (0.20); PTH 0.24 - 0.27 (0.25); PTW 0.16 - 0.18 (0.17); PPL 0.19 - 0.21 (0.20); PPH 0.23 - 0.27 (0.25); PPW 0.24 - 0.27 (0.26); CI 90 - 92 (91); SI 84 - 86 (85); OI 27 - 31 (29); DMI 55 - 58 (56); LMI 38 - 43 (41); PSLI 22 - 25 (23); PeNI 37 - 39 (38); LPeI 78 - 82 (81); DPeI 80 - 85 (82); PpNI 56 - 59 (58); LPpI 79 - 85 (82); DPpI 124 - 130 (127); PPI 147 - 156 (152).

Head significantly longer than wide (CI 90 - 92); posterior head margin moderately concave. Anterior clypeal margin entire and convex. Frontal carinae strongly developed, approaching or ending at posterior head margin. Antennal scrobes developed, but shallow and without clearly defined posterior and ventral margins. Antennal scapes moderately long, not reaching posterior head margin (SI 84 - 86). Eyes large (OI 27 - 31). 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 relatively short to medium-sized, elongate-triangular to spinose, and acute (PSLI 22 - 25); propodeal lobes short, triangular to elongate-triangular, and acute. Petiolar node in profile rectangular nodiform, approximately 1.2 to 1.3 times higher than long (LPeI 78 - 82), anterior and posterior faces approximately parallel, posterodorsal margin situated higher than anterodorsal, anterodorsal and posterodorsal angles relatively rounded, petiolar dorsum convex; node in dorsal view approximately 1.2 times longer than wide (DPeI 80 - 85). Postpetiole in profile subglobular and moderately anteroposteriorly compressed, approximately 1.2 to 1.3 times higher than long (LPpI 79 - 85); in dorsal view around 1.2 to 1.3 times wider than long (DPpI 124 - 130). Postpetiole in profile appearing less voluminous than petiolar node, in dorsal view approximately 1.5 to 1.6 times wider than petiolar node (PPI 147 - 156). Mandibles unsculptured, smooth, and shining; clypeus longitudinally rugulose, usually with three rugulae, median rugula better developed; cephalic dorsum between frontal carinae with five to eight longitudinal rugae, most rugae running unbroken from posterior clypeal margin to posterior head margin, few rugae interrupted, but none with cross-meshes; scrobal area mostly unsculptured; lateral and ventral head longitudinally rugose to reticulate-rugose. Mesosoma laterally irregularly rugose, dorsally distinctly longitudinally rugose. Forecoxae unsculptured, smooth, and shining. Petiolar node laterally weakly to moderately longitudinally rugose. Postpetiole and gaster unsculptured, smooth, and shining. Ground sculpture generally faint to absent everywhere on body. Whole body with abundant, long, and fine standing hairs; first gastral tergite without appressed pubescence. Anterior edges of antennal scapes with suberect to erect hairs. Head, mesosoma, legs, and waist segments yellowish to bright orange, contrasting with very dark brown to black gaster.

Type Material
Hita Garcia and Fisher (2013) - Holotype, pinned worker, DEMOCRATIC REPUBLIC OF CONGO, Epulu, 4.I.1949 (J.C. Bradley) MCZ examined.

References based on Global Ant Biodiversity Informatics

 * Hita Garcia F. and Fisher B.L. 2013. The Tetramorium tortuosum species group (Hymenoptera, Formicidae, Myrmicinae) revisited - taxonomic revision of the Afrotropical T. capillosum species complex. ZooKeys 299: 7799