Tetramorium aculeatum

An arboreal nester, and one of the most common Tetramorium in woodlands and forests of tropical Africa.

Identification
Bolton (1980) - As can be deduced from the description, and from the number of infraspecific and infrasubspecific names which aculeatum has acquired, this is a very variable species. The majority of the infraspecific names were based on trivial characters such as minor variations in spine length or colour, but all are connected by numerous intermediates, and I am convinced that all these forms represent a single plastic species. This is by far the commonest member of the aculeatum-group. Factors separating it from Tetramorium africanum and Tetramorium rimytyum are given under those species, and characters separating aculeatum females (queens) from others in the group are tabulated under Tetramorium rotundatum.

Distribution based on Regional Taxon Lists
Afrotropical Region: Cameroun, Democratic Republic of Congo, Ghana, Guinea, Ivory Coast, Kenya, Liberia, Senegal, Sierra Leone, Sudan, Uganda, United Republic of Tanzania.

Biology
Bolton (1980) - One of the commonest species of Tetramorium in wooded or forested zones throughout Africa, aculeatum may be locally very common. It nests and forages arboreally and is only very rarely found on the ground. The nest, a mixture of silk, vegetable fragments, fungal hyphae and other debris, is constructed under or between leaves or in the branches of trees, commonly at the junction of two or more stems or twigs. The ants are predaceous and very aggressive, and tend to exclude many other ant species from the trees which they occupy. In their role as predator and dominant species these ants are of importance in cocoa-growing areas in keeping down other insect species or, by their presence, excluding these other species from the trees which they occupy. Because of this economic importance some aspects of the ecology and biology of aculeatum have been studied. Most of the presently available information is included in Aryeetey (1971), Room (1971), Leston (1973) and Majer (1976), and in the references included in these publications.

Nomenclature

 *  aculeatum. Macromischa aculeata Mayr, 1866a: 507 (w.) GHANA. André, 1889: 224 (q.); Mayr, 1902: 292 (m.); Wheeler, G.C. & Wheeler, J. 1955b: 18 (l.). Combination in Tetramorium: Emery, 1896a: 103; in Macromischoides: Wheeler, W.M. 1920: 53; in Tetramorium: Bolton, 1976: 363 (in text); Bolton, 1980: 353. Senior synonym of andricum, inermis, major, melanogyne, militaris, pulchellus, rubroflava, viridis, wasmanni, zumpti and material of the unavailable names abdominalis, gladiator referred here: Bolton, 1980: 353.
 * wasmanni. Macromischa wasmanni Forel, 1901d: 300 (w.) DEMOCRATIC REPUBLIC OF CONGO. Mayr, 1902: 292 (q.m.). Combination in Tetramorium: Emery, 1908b: 187 (footnote); in Macromischoides: Wheeler, W.M. 1922a: 190. Subspecies of aculeatum: Emery, 1908b: 187 (footnote); Forel, 1909b: 71; Santschi, 1910c: 385; Santschi, 1924b: 208. Junior synonym of aculeatum: Bolton, 1980: 353.
 * andricum. Tetramorium aculeatum subsp. andricum Emery, 1908b: 187 (w.q.m.) DEMOCRATIC REPUBLIC OF CONGO. Combination in Macromischoides: Wheeler, W.M. 1922a: 890. Junior synonym of aculeatum: Bolton, 1980: 353.
 * major. Tetramorium aculeatum var. major Forel, 1915c: 344 (w.) DEMOCRATIC REPUBLIC OF CONGO. Combination in Macromischoides: Wheeler, W.M. 1922a: 889. Junior synonym of aculeatum: Bolton, 1980: 353.
 * rubroflava. Tetramorium aculeatum var. rubroflava Forel, 1916: 420 (w.) DEMOCRATIC REPUBLIC OF CONGO. Junior synonym of aculeatum: Bolton, 1980: 353.
 * melanogyne. Macromischoides aculeatus var. melanogyne Santschi, 1923e: 285 (w.q.) CONGO. [Unresolved junior secondary homonym of melanogyna Mann, above.] Junior synonym of aculeatum: Bolton, 1980: 353.
 * militaris. Macromischoides aculeatus st. militaris Santschi, 1924b: 209, fig. 8 (w.) DEMOCRATIC REPUBLIC OF CONGO. Junior synonym of aculeatum: Bolton, 1980: 353.
 * pulchellus. Macromischoides aculeatus var. pulchellus Santschi, 1924b: 208, fig. 8 (w.q.m.) DEMOCRATIC REPUBLIC OF CONGO. [Unresolved junior secondary homonym of pulchellum Emery, above.] Junior synonym of aculeatum: Bolton, 1980: 353.
 * zumpti. Macromischoides zumpti Santschi, 1937b: 101, fig. 4 (w.) CAMEROUN. Junior synonym of aculeatum: Bolton, 1980: 353.
 * viridis. Macromischoides viridis Weber, 1943c: 367, pl. 15, fig. 9 (w.q.m.) SUDAN. Junior synonym of aculeatum: Bolton, 1980: 353.
 * inermis. Macromischoides aculeatus r. inermis Bernard, 1953b: 249 (w.) GUINEA. [Unresolved junior secondary homonym of inerme Mayr, above.] Junior synonym of aculeatum: Bolton, 1980: 353.

Worker
Bolton (1980) - TL 3.2-5.4, HL 0.74-1.20, HW 0.66-1.08, CI 85-90, SL 0.88-1.34, SI 124-150, PW 0.48-0.80, AL 0.90-1.60 (50 measured).

Mandibles usually superficially shagreened or punctulate but very commonly virtually smooth, only rarely with delicate striate sculpture. Masticatory margin armed with 3 teeth apically, followed by a row of 5-7 denticles, the second denticle in the series usually larger than the first. Anterior clypeal margin most commonly with a median notch or impression, but the shape and size of this varies considerably between different series. In some the clypeal margin is more or less evenly arcuate medially, without an impression, but this grades into forms in which the margin is flattened medially, then slightly excavated, then shallowly impressed, and the sequence continues until forms with a distinct notch are encountered. Median clypeal carina usually absent, the central strip of the clypeus often finely punctate. Fine carinae are common on the lateral portions of the clypeal shield but development of a median carina is rare and is generally encountered only in larger individuals, though this is by no means a rule as many large specimens show no trace of a carina. Frontal carinae weakly or not developed, ending at or in front of the level of the posterior margins of the eyes, sometimes indistinguishable from the other cephalic sculpture and often vestigial. Scapes long (SI > 100 and SL > HL); when laid back on the head always easily exceeding the occipital corners. Antennal scrobes absent. Eyes strongly prominent on sides of head in full-face view, maximum diameter of eye 0.17-0.28, about 0.26-0.30 x HW. With the head in full-face view the sides behind the eyes rounding broadly and evenly into the occipital margin, without obvious occipital corners. Anterior pronotal corners (shoulders) rounded in dorsal view but the sides of the pronotum each with a dorsolateral tumulus or prominence, which in some populations is very conspicuous. With the alitrunk in profile the metanotal groove is usually impressed and the propodeal dorsum just behind the groove is raised into a low welt, though depth of impression and development of the welt are both variable and one or both may be inconspicuous. Propodeal spines enormously variable in length, thickness and degree of elevation. In general they are long, strong and acute but they may be reduced to vestiges; the extremes are shown in Fig. 130. Metapleural lobes at most a pair of very low inconspicuous triangular plates, usually slightly prominent but sometimes so low as to be invisible in profile. Petiole in profile with a long, narrow anterior peduncle and a narrow node, the length of the peduncle distinctly much greater than the thickness of the node at its mid-height. In dorsal view the node transverse, much broader than long, sometimes transversely narrowly ovate in shape but generally with the anterior face more convex than the posterior. Dorsum of head longitudinally rugose and usually with a reticulum occipitally, but the density and intensity of the rugosity variable. In general larger individuals are more strongly sculptured, the rugae more closely packed and with a tendency to radiate outwards posteriorly. In small workers the rugae tend to be weaker and sparser, often with broad unsculptured spaces between them. In such small forms the occipital reticulum usually vanishes, but some quite strongly sculptured small workers are known as well as a few relatively lightly marked large individuals, but the latter are rare. Dorsal alitrunk rugose, predominantly longitudinally so but sometimes with scattered cross-meshes. Dorsal surface of petiole often with fine longitudinal rugulae, but the sculpture may be partially or entirely effaced, leaving the surface superficially punctulate or even smooth. Postpetiole smooth dorsally or with fine punctulation, quite frequently also with fine longitudinal rugulae which vary considerably in number and strength. First gastral tergite smooth or at most with very fine faint superficial patterning. All dorsal surfaces of head and body densely clothed with fine acute hairs of verying length. Scapes and tibiae with numerous outstanding fine hairs. Colour varying from uniform light brown to uniform black or blackish brown. Quite commonly the gaster is somewhat lighter in shade than the head and alitrunk.

Type Material
Bolton (1980) - Syntype workers, GHANA [examined].

References based on Global Ant Biodiversity Informatics

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