Tetramorium aculeatum (Mayr)

Type location Ghana (Macromischa aculeata, Mayr, 1866a: 507, worker; André, 1889: 224, queen; Mayr, 1902: 292, male); junior synonyms andricum (Emery, 1908b: 187, all forms) collected at Kisangani [Stanleyville] by H. Kohl, major (Forel, 1915c: 344, worker) collected at St. Gabriel, by Kohl, militaris (Santschi, 1924b: 209, illustrated, worker) collected at Basongo by H. Schouteden, pulchellus (Santschi, 1924b: 208, illustrated, worker), rubroflava (Forel, 1916: 420, worker) collected at St. Gabriel, by Kohl; and wasmanni (Macromischa wasmanni n. sp, Forel, 1901d: 300, worker; Mayr, 1902: 292, queen & male) from Kinshasa [Leopoldville], collected by Wasmann - all from Zaïre, inermis (Bernard, 1952: 249, worker) from Guinea, Mt. Nimba, at G'ba, by Lamotte; melanogyne (Santschi, 1923e: 285, worker & queen) from Congo, Brazzaville, by A. Weiss; viridis (Weber, 1943c: 367, illustrated, all forms) from Sudan, zumpti (Macromiscoides sp. zumpti n. sp., Santschi, 1937b: 101, illustrated, worker) from Cameroun, Kumba, by F. Zumpt, 12-16.x.1935; and material of unavailable names abdominalis (Santschi, 1924b: 209, illustrated) collected at Kasai, Kondu, by E. Luja, and gladiator (Santschi, 1919c: 248) from Zaïre, Congo da Lemba by R. Mayné; all forms known i(see Bolton, 1995) .

Mayr's (1866a) description is at . André's (1889) description of the queen is at . Forel's (1901d) description of wasmanni is at . Mayr's (1902) notes are at . Emery's (1908b) description of andricum, together with his thinking on the species being a Tetramorium is at . Santschi (1910c: 385) had notes, these are at . Forel's (1915c) description of major is at . Forel (1916) has further notes and a description of rubroflava at . Santschi's (1919c) description of gladiator is at . Santschi's (1923e) description of melanogyne is at . Santschi's (1924b) descriptions of pulchellus, abdominalis and militaris, plus an illustrated comparison of the propodeum and pedicel forms, and a key to the varieties, is at . Santschi's (1937b) description of zumpti is at . Weber's (1943c) description of viridis is at . Bolton's modern description (1980) is at .

WORKER (Nigeria specimens from CRIN) - Size variable but TL around 4.00-4.40 mm. Larger specimens HL 0.93, HW 0.84, SL 1.17, PW 0.58 (in my guide as Macromischoides aculeatus)

Bolton (1980: 353, illustration only of alitrunk variability and pedicel) described it as a very variable species, that being the source of the large number of subspecies, strains and varieties which previously had been described. Thus, the variant described and illustrated below has to be regarded as aculeatum.

Colour dark brown but somewhat variable. Sculpturation primarily of rather sinuous longitudinal rugae on the head, alitrunk and, more faintly, the pedicel. Abundant erect hairs all over. Mandible denticles moderately developed. Clypeus near flat, smooth and the margin entire. Head with a nearly perfect oval shape in full face view; short frontal carinae, no antennal scrobes. Petiole with a long, narrow, anterior peduncle.

Tetramorium aculeatum (Mayr), colour variant

WORKER (Nigeria specimen) TL 5.29 mm, HL 0.96, HW 1.12, SL 1.28, PW 0.78 (in my guide as Macromischoides species T¹)

Colour very dark red-brown. Sculpturation rugoreticulate, rugae dominant, on head and alitrunk, longitudinal except on dorsal pronotum, where transversely arcuate, and oblique on the lateral mesonotum. Abundant rather coarse long hairs all over. Mandibles with denticles much reduced except the apical pair. Clypeus with spiculate central area and anteriorly marginate. Frontal carinae of head short and no antennal scrobes. Metanotal groove impressed; propodeum with a pronounced anterior dorsal carina; propodeal spines noticeably curved upwards but relatively short when compared to the common T. aculeatum.

In Nigeria, I collected a single specimen from a vine on a shade tree in a cocoa plot (Onipe 1/1, Plot C) at CRIN. It is very distinctive in appearance and is larger than the queen of the common T. aculeatum, which was found on neighbouring cocoa trees. Thus, despite Bolton's determination of it as aculeatum (personal communication, 1976), it seems to merit the separate treatment and the drawing. In general the features all fit those described for the larger specimens by Bolton (1980). An alternative is that it was a specimen of Tetramorium rimytyum or that rimytyum merits no better status than that of a variety of aculeatum.

See - Comparison of described varieties

The photomontage is of a specimen from the Central African Republic, Dzanga-Sangha NP; site EE; 31.i.2005; 02°49’07.9" N 16°09’28.3" E 377m; Camp 2; prélèvements à 35-40m du sol dans un Azobé (Lophira alata, Ochnaceae), 11h-17h; collector Philippe Annoyer. . Other images can be seen in the folders at - . Further specimens from Dzanga-Sangha NP, Camp 3; 17.ii.2005, 02°53’25.9" N 16°10’26.4" E 409m, seen 1300 to 1800, collector Philippe Annoyer, are at .

Forel (1909d), reporting specimens from Sankuru, Zaïre, collected by Luja, noted that his variety wasmanni was a small form with very short propodeal spines, including on the female. Later (1915c) he described the variety major - TL 4.2-4.8; black; appendages and mandibles brown; gaster and pedicel of petiole red-brown; otherwise as type but simply much larger; from St. Gabriel, Zaïre, by Kohl, constructing larger more solid nests than wasmanni.

Common throughout West Africa. Wheeler (1922) listed findings from Guinea (Los Islands, H. Brauns), Sierra Leone (Mocquerys), Cameroun (Sjöstedt; Abo by R. Buchholz; Victoria, F. Silvestri; Ekona, by Hintz) and many Congo locations.

A very widely distributed, major dominant of closed canopy cocoa, on up to 15% of trees in Nigeria (Booker, 1968; Taylor, 1977; Taylor & Adedoyin, 1978), and other tree crops with suitable, large softish leaves on the underside of which, or between which, the ants build their well-known 'felt' nests (right, clickable image). Tends Homoptera, including the report by Adenuga & Adeboyeku (1987) of it attending Pseudococcus hargreavesi. Also found on native shrubs and trees, and on cashew, coffee and kola.

Its biology in Ghana was described by Strickland (1951a, as M. aculeatus), who noted a negative association with mealybugs and their attendant ant species. Leston (1973) also regarded it as a dominant, writing that it needs areas of good dense canopy cocoa or cocoa under fairly heavy top shade. Later it was collected from cocoa canopy and herbs under cocoa by Room (1971) at the Mampong Cemetery farm, plus 19 collections from the 168 samples of insolated cocoa canopy. He described it as a potentially common dominant which rarely holds a large territory, and established a negative association with Oecophylla longinoda. Majer (1972) (also as M. aculeatus) found it to be a clear dominant on cocoa at Kade; he later described finding it in 70% of his 144 pkd samples at Kade, with around 1500 workers per sample (Majer 1975, 1976a, b, c). Also from cocoa mistletoe (Room, 1975). Bigger (1981a) recorded as one of the three most common species on a block of Amelonado cocoa at CRIG, occupying areas inhabited also by Crematogaster clariventris and avoiding Oecophylla longinoda. At that stage Bigger referred to it as a sub-dominant, arguing that it was inadequately aggressive to counter the true dominants. Later, he seems to accept it as a true dominant (Bigger, 1993b) and Campbell (1994) argues that it dominates cocoa lacking in Homoptera. On a wider scale, it was found on leaf litter, as a 'tourist', at Kade, under cocoa, and the Atewa Forest Reserve, under primary and secondary forest, by Belshaw & Bolton (1994b). Strickland (1951a) also described it being found nesting on kola, plantain and several forest trees, adding that it did not appear to have any marked host preferences.

Bernard (1952) reporting the Mt. Nimba survey work in Guinea, noted that curiously few specimens were collected by Lamotte. The new subspecies "inermis" was based on 6 workers found on a path at G'ba; the specimens being close to the race andricum, a small form known from Congo and Uganda, but the Nimba specimens had the propodeal spines (normally long) reduced to short teeth. In a footnote, Bernard added that workers had been sent to him by A. Balachowsky, from a "station lower in Guinea"; "very aggressive, the workers had a remarkable clavigerid Coleopteran in their nest".
[E.B. Britton, in Insects of Australia, Melbourne University Press, 1972, Chapter 30, Coleoptera, has an illustration (p. 546) of such a beetle, noting "the CLAVIGERINAE (Coleoptera: Pselaphidae) are specialised for life in ants' nests, having highly modified antennae, reduced maxillary palps, and trichomes in the form of a hollow or hollows at the base of the abdomen surrounded by tufts of yellow hair".]
Bernard also reported the collection of two dealated queens of ssp "andricum" from station B 8-40, N'Zo and Mount Tô at 1600 m; and, a single yellowish male of "Macromischoides sp." from Zouépo (B6-100), this had a slimmer thorax, with brown spots and two obtuse epinotal teeth, he could not be certain if it was a male of inermis, as the male of andricum was very different.

Jackson (1984) found it as the dominant on 28-30% of cocoa trees in two study plots at Nko'emvon in Cameroun. She described how it was negatively associated with Crematogaster africana, Crematogaster gabonenis and Oecophylla longinoda but thought its habitat preference was for thinner canopy - thus differing from the situation in Ghana and Nigeria. The latter difference she ascribed to perhaps being a result of opportunity for colonisation and its relations with the other dominants.

In Liberia it was common on trees at lowland and upland areas (Carroll, 1979).