Tetramorium weitzeckeri

Tetramorium weitzeckeri is a common and widely distributed savannah or open area species.

Identification


The following character set divides T. weitzeckeri from other species of the complex: SI 77 - 84; propodeal spines long and spinose (PSLI 32 - 45); head and mesosoma strongly longitudinally rugose, ground sculpturation mostly effaced, generally smooth and shiny; standing hairs present on first gastral tergite; coloration uniformly light brown to nearly black. (Hita Garcia et al. 2010)

Allied to Tetramorium occidentale, Santschi, but differing by the length of the antennal joints, by the sculptured head and thorax and mandibles. The nodes of the petiole are thinner, i.e. much more compressed from front to back than in Tetramorium humbloti Forel. Durban. A small nest under a stone.

A member of the Afrotropical weitzeckeri species complex, which is part of the weitzeckeri species group.

Key to weitzeckeri-group species.

Distribution
Eastern and Southern Africa, generally up north to the Equatorial tropical rain forest belt.

Distribution based on Regional Taxon Lists
Afrotropical Region: Eritrea, Kenya, Mozambique, Namibia, South Africa, Sudan, Swaziland, Tanzania, Zambia, Zimbabwe. Palaearctic Region: Ethiopia.

Nomenclature

 *  weitzeckeri. Tetramorium (Xiphomyrmex) weitzeckeri Emery, 1895h: 39 (w.) SOUTH AFRICA. Arnold, 1917: 346 (q.). Combination in Xiphomyrmex: Wheeler, W.M. 1922a: 908; in Tetramorium: Bolton, 1980: 233. Senior synonym of ebeninum, edithae, escherichi, nigellus: Bolton, 1980: 233. See also: Hita Garcia, Fischer & Peters, 2010b: 85.
 * escherichi. Tetramorium (Xiphomyrmex) escherichi Forel, 1910c: 259 (w.q.) ETHIOPIA. Combination in Xiphomyrmex: Emery, 1915g: 4. Junior synonym of weitzeckeri: Bolton, 1980: 233.
 * ebeninum. Tetramorium (Xiphomyrmex) ebeninum Arnold, 1926: 277, fig. 80 (w.) SOUTH AFRICA. Junior synonym of weitzeckeri: Bolton, 1980: 233.
 * nigellus. Xiphomyrmex weitzeckeri var. nigellus Santschi, 1932a: 389 (w.q.) ZIMBABWE. Junior synonym of weitzeckeri: Bolton, 1980: 233.
 * edithae. Xiphomyrmex weitzeckeri subsp. edithae Weber, 1943c: 375 (w.) SUDAN. Junior synonym of weitzeckeri: Bolton, 233.

Hita Garcia et al. (2010) - Tetramorium weitzeckeri together with Tetramorium boltoni, Tetramorium renae, and Tetramorium snellingi form a compact core of morphologically related species within the weitzeckeri complex. They can be easily distinguished from Tetramorium bendai, Tetramorium humbloti, Tetramorium sepultum, and Tetramorium tanaense by the presence of standing hairs on the first gastral tergite, and from Tetramorium guineense by their absence of a conspicuous reticulate-punctate cephalic ground sculpturation characteristic for the latter. The separation of T. boltoni from T. weitzeckeri is based on morphological differences in the development of the antennal scapes and propodeal spines, biogeography, and habitat preference, and is discussed in detail in the description of T. boltoni. Furthermore, T. weitzeckeri can be simply distinguished from T. snellingi because the latter is much smaller in size, possesses much smaller spines, and is distinctly bicoloured, and from T. renae since this species is smaller in size and bicoloured, too, and distinctly less sculptured on the mesosoma.

Taking into account that the previous species description of T. weitzeckeri was unable to discriminate between the latter and T. boltoni, T. renae, and T. snellingi, it was necessary to redefine the description of T. weitzeckeri. Yet, it has to be mentioned that T. weitzeckeri is still a relatively variable species but to a much lower degree as previously thought, and always within a species-specific range. For example some populations in South Africa tend to have distinctly shorter hairs than observed in most East African or other Southern African populations. Nevertheless, this is treated as intraspecific variation since it is the only observable difference within these populations and it does not occur consistently enough throughout the entire distribution range. The same applies to small variations in cephalic ground sculpturation, size, and coloration observed in some other populations. However, a series of specimens sampled in Arabuko Sokoke Forest, Coastal Kenya, varied a bit more than usual in being smaller, much darker coloured (nearly black), and in having the anterior clypeal margin only weakly impressed. Also the mesosomal sculpturation was weaker developed than in all the other examined T. weitzeckeri material. Thus, there is a strong possibility that there is still more than one "good" species included within the actual definition of T. weitzeckeri but this problem cannot be resolved with this study.

Description
Jet-black; legs, antennae and mandibles dark piceous brown, the apical half of the last antennal joint and the last four joints of the tarsi, testaceous. Head and thorax moderately shining, the former longitudinally and coarsely striato-rugose, the sides of the head and thorax more closely sculptured and with transverse striae in addition, the demiscrobe almost smooth over its posterior two-thirds. Petiole, legs and abdomen smooth and very shining. Mandibles closely striate, with a row of large punctures behind the masticatory margin. Clypeus with a strong median carina. Legs and antennae with a sparse, long and yellowish pubescence; head and thorax with a scanty, outstanding and pale pilosity. Head subrectangular, about one-fifth longer than wide, (excluding the mandibles), the sides in front of the eyes parallel, behind them somewhat convex, the posterior angles rounded, the posterior margin moderately concave. The eyes are very prominent and convex, placed in the middle of the sides. Second and 3rd joints of the flagellum a little wider than long, the 4th and 5th as wide as long, the rest longer than wide. The frontal carinae, which extend back to the posterior margin of the head, are moderately divergent backwards, and form the upper boundary of the distinct demi-scrobes; the scapes do not quite reach the posterior margin. Anterior margin of clypeus feebly impressed in the middle. Anterior margin of the pronotum arcuate, the shoulders subangular. Thoracic sutures obsolete above, the dorsu of the epinotum separated from the mesonotum by a raised and sharp line. The dorsum of the epinotum is about as long as wide, slightly hollowed out; the epinotal spines long and acute, strongly divergent, almost twice as long as they are wide at the base, uite twice as long as the space between their bases; episternal teeth triangular, acute, one-third as long as the epinotal; the declivity smooth and shining. Node of the 1st joint of the petiole squamiform, higher than its peduncle is long, and higher than the 2nd node. Its anterior face is convex from side to side, the posterior face flat, its dorsal edge convex transversely and moderately rounded from front to back. The 2nd node two and a third times wider than long, one-third wider than the 1st, its upper half compressed from front to back, (more so at the sides than in the middle), the anterior face vertical, a little wider in front than behind. Abdomen oval.

Worker
Hita Garcia et al. (2010) - HL 0.789 - 0.944 (0.867); HW 0.772 - 0.933 (0.839); SL 0.600 - 0.744 (0.671); EL 0.167 - 0.222 (0.196); PW 0.578 - 0.711 (0.639); WL 0.911 - 1.206 (1.047); PSL 0.278 - 0.411 (0.330); PTL 0.122 - 0.156 (0.135); PTH 0.344 - 0.461 (0.390); PTW 0.300 - 0.400 (0.339); PPL 0.189 - 0.244 (0.215); PPH 0.344 - 0.467 (0.394); PPW 0.356 - 0.444 (0.404); CI 93 - 100 (97); SI 77 - 84 (80); OI 21 - 26 (23); PSLI 32 - 45 (38); PeNI 47 - 58 (53); LPeI 28 - 38 (34); DPeI 219 - 295 (251); PpNI 59 - 69 (63); LPpI 49 - 60 (55); DPpI 172 - 203(189); PPI 110 - 129 (119) (52 measured).

Head slightly longer than wide, sometimes as long as wide (CI 93 - 100). Anterior clypeal margin with distinct median impression. Frontal carinae strongly developed, becoming weaker behind level of eye and ending shortly before posterior margin of head. Antennal scrobe narrow, shallow, and without defined ventral margin. Antennal scape of moderate length, not reaching posterior margin of head (SI 77 - 84). Eyes small to moderate (OI 21 - 26), with 9 to 12 ommatidia in longest row. Metanotal groove in profile weakly impressed. Propodeal spines very long (PSLI 32 - 45), spinose with acute apex. Propodeal lobes small, triangular and acute. Petiolar node strongly squamiform, in dorsal view between 2 and 3 times wider than long (DPeI 219 - 272) and in lateral view between 2.6 to 3.5 times higher than long (LPeI 28 - 38). Postpetiole in dorsal view between 1.5 to 2 times wider than long (DPpI 172 - 202) and much more voluminous than petiole; in profile squamiform but thicker compared to petiole, between 1.6 to 2.1 times higher than long (LPpI 48 - 60). Mandibles distinctly longitudinally striate. Clypeus usually with 3 to 5 longitudinal rugae, median ruga always more strongly developed and unbroken, while lateral rugae variable in strength and length. Dorsum of head, as well as lateral part ventral to scrobe, longitudinally rugose with widely spaced rugae, usually with 7 to 9 longitudinal rugae between frontal carinae, almost all running unbroken to posterior margin of head. Spaces between rugae with very weak, nearly effaced ground sculpture or completely unsculptured, generally quite shiny. Scrobal area with reduced punctate ground sculpture or completely unsculptured. Mesosoma dorsally and laterally with distinct, mostly longitudinal, widely spaced rugae. Spaces between them and propodeal declivity unsculptured, smooth and shiny. Petiole, postpetiole and gaster completely unsculptured, smooth and shiny. All dorsal surfaces of head, mesosoma, both waist segments and gaster with abundant, long, fine, and simple suberect to erect hairs. Fine pubescence on tibiae and antennal scapes appressed to decumbent. Body uniformly brown, colour varies from light brown to very dark brown, nearly black.

Type Material
Hita Garcia et al. (2010) :

Holotype worker, SOUTH AFRICA, Natal, Verulam, leg. Weitzecker (: ZFMK_HYM_2009_6086) [examined].

Tetramorium (Xiphomyrmex) escherichi Syntype workers, female, ERITREA, Ghinda, Nefasit, leg. Escherich [examined].

Tetramorium (Xiphomyrmex) ebeninum  Syntype workers, SOUTH AFRICA, Natal, Durban, 27.IX.1918, leg. G. Arnold [examined].

Xiphomyrmex weitzeckeri var. nigellus Syntype worker, female, ZIMBABWE, Vumba Mts, 5700ft (1740m), 2.-15.II.1921, leg. G. Arnold [examined].

Xiphomyrmex weitzeckeri subsp. edithae Holotype worker, SUDAN, Imatong Mts, 6000 ft (1830m), 2.VIII.1939, leg. N.A. Weber [examined].

Determination Clarifications
Hita Garcia et al. (2010) - All distribution records of T. weitzeckeri from previous studies have to be treated with caution. It seems that all earlier records from Nigeria, Cameroon, D.R. Congo, Central African Republic, and Uganda have to be assigned now to Tetramorium boltoni while only the East and Southern African specimens are genuine T. weitzeckeri. Both species can be found in localities in Angola, Kenya, and Sudan where savannah and rain forest habitats are in close proximity but always separated in their respective habitats.

Additional References

 * Hita Garcia, F.; Fischer, G.; Peters, M. K. 2010. Taxonomy of the Tetramorium weitzeckeri species group (Hymenoptera: Formicidae) in the Afrotropical zoogeographical region. Zootaxa 2704:1-90.