Tetramorium uelense Santschi, 1923

Hita Garcia, Francisco & Fisher, Brian L., 2014, The ant genus Tetramorium Mayr in the Afrotropical region (Hymenoptera, Formicidae, Myrmicinae): synonymisation of Decamorium Forel under Tetramorium, and taxonomic revision of the T. decem species group, ZooKeys 411, pp. 67-103 : 83-86

Tetramorium uelense Santschi, 1923 comb. r. Figs 3, 4B, 5C, 5D, 10

Tetramorium (Decamorium) decem uelense Santschi, 1923: 285. [Combination in Decamorium and raised to species by Bolton 1976: 298.]

Decamorium decem nimba Bernard, 1953: 250. [Junior synonym of Tetramorium uelense by Bolton 1976: 298; here confirmed.]

Type material.

Of uelense:lectotype, pinned worker, D. R. CONGO (Congo belge), Uelé, Vankerhovenville, 3.0N, 29.5E (Degreef) (NHMB: CASENT0906826) [examined]. Paralectotype, pinned queen with same data as lectotype (MRAC) [not examined].

Of nimba:holotype, pinned worker, GUINEA, Kéoulenta, 7.714053N, 8.331786W, St. 1 Savane, (MNHN: CASENT0914084) [examined].

[Note: GPS data for neither of the type localities was included on the locality labels or the original descriptions. The data presented above is based on our own geo-referencing of Vankerhovenville located in Province Orientale and Kéoulenta located in the Nzérékoré Region. Consequently, they should be considered approximations and not the exact positions of the type localities.]

Non-type material.

GHANA: Greater Accra Region, Accra Metropolis District, Legon, 23.VIII.1972 (D. Leston); NIGERIA: 16 km N. of Mokwa, 16.X.1976 (C. Longhurst).

Diagnosis.

The following character combination separates Tetramorium uelense from the other species of the Tetramorium decem species group: relatively larger species (WL 0.98-1.06); propodeum armed with short triangular to elongate-triangular teeth (PSLI 16-18); petiolar node in profile around 1.1 times higher than long (LPeI 88-93); dorsum of mesosoma conspicuously longitudinally rugose with distinctive reticulate-punctate ground sculpture; strongly bicoloured with dark brown to black gaster contrasting with light brown to reddish brown remainder of body.

Worker measurements

(N=6). HL 0.67-0.72 (0.70); HW 0.54-0.59 (0.57); SL 0.39-0.42 (0.41); EL 0.19-0.20 (0.20); PH 0.36-0.38 (0.37); PW 0.43-0.47 (0.45); WL 0.98-1.06 (1.02); PSL 0.11-0.13 (0.10); PTL 0.27-0.29 (0.28); PTH 0.29-0.32 (0.31); PTW 0.21-0.23 (0.22); PPL 0.24-0.26 (0.25); PPH 0.28-0.34 (0.31); PPW 0.30-0.33 (0.31); CI 80-83 (81); SI 69-74 (72); OI 34-35 (35); DMI 43-44 (44); LMI 35-37 (36); PSLI 16-18 (17); PeNI 48-49 (49); LPeI 88-93 (90); DPeI 77-81 (79); PpNI 69-70 (70); LPpI 75-86 (80); DPpI 122-125 (124); PPI 141-145 (143).

Worker description.

Head much longer than wide (CI 80-83); posterior head margin weakly concave. Anterior clypeal margin with distinct, but often shallow median impression. Frontal carinae strongly developed and noticeably raised forming dorsal margin of very well-developed antennal scrobes, curving down ventrally and anteriorly halfway between posterior eye margin and posterior head margin and forming posterior and ventral scrobe margins; antennal scrobes very well developed, deep and with clearly defined margins, but ventral margin less strongly developed, median scrobal carina absent. Antennal scapes short, far from reaching posterior head margin (SI 69-74). Eyes relatively large (OI 34-35). Mesosomal outline in profile relatively flat, elongate and low (LMI 35-37), moderately to strongly marginate from lateral to dorsal mesosoma; promesonotal suture absent; metanotal groove present, distinct, but relatively shallow. Propodeum armed with short, triangular to elongate-triangular, and acute teeth (PSLI 16-18), propodeal lobes reduced, short, and well rounded, usually shorter than propodeal teeth. Tibiae and femorae strongly swollen. Petiolar node nodiform with moderately rounded antero- and posterodorsal margins, in profile around 1.1 times higher than long (LPeI 88-93), anterior and posterior faces approximately parallel, anterodorsal and posterodorsal margins situated at about same height and equally angled, petiolar dorsum clearly convex; node in dorsal view around 1.2 to 1.3 times longer than wide (DPeI 77-81), in dorsal view pronotum between 2.0 and 2.1 times wider than petiolar node (PeNI 48-49). Postpetiole in profile globular, approximately 1.2 to 1.3 times higher than long (LPpI 75-86); in dorsal view between 1.2 and 1.3 times wider than long (DPpI 122-125), pronotum around 1.4 times wider than postpetiole (PpNI 69-70). Postpetiole in profile more or less of same volume as petiolar node, postpetiole in dorsal view around 1.4 times wider than petiolar node (PPI 141-145). Mandibles and clypeus unsculptured, smooth, and shining; cephalic dorsum between frontal carinae with fine irregularly longitudinally rugulose/rugose sculpture, rugulae/rugae often interrupted, meandering, or with cross-meshes, cephalic dorsum also puncticulate to punctate throughout its length; scrobal area strongly reticulate-punctate; lateral head mainly reticulate-rugose with weak to moderately well developed punctate ground sculpture. Ground sculpture on head usually weak, except scrobal area (see above). Dorsum of mesosoma densely longitudinally rugose on top of strong punctate ground sculpture; lateral mesosoma longitudinally rugose and very conspicuously reticulate-punctate. Forecoxae unsculptured, smooth, and shining. Petiolar node and postpetiole superficially longitudinally rugulose or irregularly rugulose superimposed on conspicuous but relatively weak reticulate-punctate ground sculpture. Mesosoma and waist segments appearing matt. First gastral tergite unsculptured, smooth, and shiny. Pilosity and pubescence greatly reduced: head with few pairs of moderately long, standing hairs, anterior pronotum with one long pair, waist segments sometimes with one long pair each, and sometimes first gastral tergite with one long pair; appressed pu bescence present everywhere on body, but noticeable only on antennae, cephalic dorsum, legs, and first gastral tergite. Anterior edges of antennal scapes and dorsal (outer) surfaces of hind tibiae with appressed hairs. Body strongly bicoloured with dark brown to black gaster contrasting with light brown to reddish brown remainder.

Distribution and biology.

So far, Tetramorium uelense is known from a few collections in savannah habitats throughout a relatively wide geographical range from West to Central Africa (Fig. 3). The known distribution spans Guinea through Ghana and Nigeria to the northeast of the D. R. Congo close to South Sudan and Uganda. Compared to most other Afrotropical Tetramorium species, there is a wealth of information about the natural history of Tetramorium uelense (Longhurst, 1979). Longhurst et al. (1979) provided important observation data about nests, foraging, recruitment, and predation on termites. Tetramorium uelense live in subterranean nests difficult to locate without observing foraging workers. At least in the area observed by Longurst et al. (1979), the main prey of Tetramorium uelense consisted of various species of Microtermes Wasmann, and Tetramorium uelense exerted great predation pressure on these small termites. Scouting is performed by solitary workers that search the leaf litter, fallen grass stems or pieces of wood for prey. After locating termites the scouts return to the colony for recruitment of groups between 10 to 30 workers. These groups locate, immobilise, and retrieve the prey. For more details refer to Longhurst et al. (1979).

Discussion.

Tetramorium uelense can be easily distinguished from the remainder of the Tetramorium decem species group. The presence of longitudinally rugose sculpture on the dorsum of the mesosoma separates Tetramorium uelense immediately from Tetramorium decem , Tetramorium ultor , and Tetramorium venator . In the latter three the mesosomal dorsum is completely unsculptured, smooth, and very shiny. The only other species with sculpture on the dorsum of the mesosoma, which could be confused with Tetramorium uelense , is Tetramorium raptor . Nevertheless, both are well separable in morphology and ecology. Most obviously, Tetramorium uelense is a larger species (WL 0.98-1.06) with distinct bicolouration while Tetramorium raptor (WL 0.88-0.93) is smaller and a uniform dark brown colour. In addition, Tetramorium uelense has longer and better developed propodeal teeth (PSLI 16-18) compared to Tetramorium raptor (PSLI 10-11), even though this might be difficult to see and may require measurements to confirm. Another, more visible character is the sculpture on the mesosomal dorsum, which is strongly longitudinally rugose with distinct punctate ground sculpture in Tetramorium uelense versus longitudinally rugulose with very little ground sculpture in Tetramorium raptor . Also, the lateral pronotum of the latter is mostly unsculptured, smooth, and shiny while in Tetramorium uelense the lateral pronotum is strongly rugose with conspicuous ground sculpture.

Variation.

Despite the broad distribution range, we did not observe any significant intraspecific variation in Tetramorium uelense .