Monomorium anceps

Identification
Bolton (1987):

As the three names australe, anceps and termitarium constitute a very close triad which may represent only one real species, the usual format of the revision is abandoned here so that the three may be considered together.

These three southern African forms are retained for the present as separate species until more material is collected for study, at which time it may be possible to show whether they are indeed separate or whether two or all of them are synonymous. All three are represented only by short syntypic series at the time of writing. The three together are characterized by the following snared characters within the salomonis group.

Relatively small forms, their combined dimensions being TL 2.4-2.6, HL 0.60-0.66, HW 0.46-0.52, CI 75-79, SL 0.47-0.54, SI 100-104, PW 0.30-0.35, AL 0.68.0-76. Maximum diameter of eye 0.24-0.26 x HW and with 7-9 ommatidia in the longest row. [Note that this combined range of dimensions is no greater than those frequently encountered in what are indubitably single species elsewhere in this species-group.]

Head with feebly developed shagreenate-granular sculpture so that the cephalic dorsum appears weakly shining and semi-smooth. Dorsal alitrunk lacking standing hairs of any description. Petiole with a single pair of backward directed hairs, postpetiole with 1-2 pairs of hairs. First gastral tergite with 2-3 pairs of hairs in front of the apical transverse row, the hairs confined to the basal half of the sclerite.

Within the limits of this diagnosis the dimensions of the three are as follows.

M. termitarium syntypes, TL 2.5-2.6, HL 0.60-0.64, HW 0.46-0.51, CI 75-79, SL 0.48-0.53, SI 100-104, PW 0.30-0.35, AL 0.70-0.76; maximum diameter of eye 0.24-0.25 x HW, with 7-8 ommatidia in the longest row (6 measured).

M. australe syntypes, TL 2.5-2.6, HL 0.64-0.66, HW 0.50-0.52, CI 78-79, SL 0.50-0.54, SI 100-104, PW 0.32-0.34, AL 0.74-0.76; maximum diameter of eye 0.25-0.26 x HW, with 9 ommatidia in the longest row (4 measured).

M. anceps syntypes, TL 2.4, HL 0.60, HW 0.47, CI 78, SL 0.47, SI 100, PW 0.30, AL 0.68; maximum diameter of eye 0.26 x HW, with 7-8 ommatidia in the longest row (2 measured).

Characters which presently serve to isolate the three syntypic series include colour, sculpture and gastral pilosity, but all are weak and may prove to be gradient. For the present the differentiation is as follows.

M. termitarium is a uniformly yellow species from Botswana in which the mesonotal dorsum is superficially reticulate-punctate. The pronotal dorsum is similarly sculptured but the sculpture is more reduced and somewhat effaced so that the punctures are vestigial. In other words the pronotal dorsal sculpture is obviously a reduced and effaced version of that seen on the mesonotum. Two pairs of hairs are present on the basal half of the first gastral tergite.

M. australe, from Cape Province, South Africa, is a medium brown species with a darker brown gaster. Dorsal alitrunk sculpture corresponds with the above, being reticulate-punctate on the mesonotum and feebly reticulate on the pronotum, again the pronotal sculpture obviously a reduced and effaced version ofthe mesonotal. The syntypes show varying degrees of abrasion but it appears that two pairs of hairs occur on the basal half of the first gastral tergite.

M. anceps, from Transvaal, South Africa, is medium brown with a darker brown gaster. The mesonotal dorsum is sharply reticulate-punctate whilst the pronotal dorsum is finely shagreenate. In other words the two areas show distinctly contrasting sculpture and the pronotal component does not appear to be merely a reduced and effaced version of that seen on the mesonotum. Three pairs of hairs occur on the basal half of the first gastral tergite.

Distribution based on Regional Taxon Lists
Afrotropical Region: South Africa.

Nomenclature

 *  anceps. Monomorium subopacum var. anceps Emery, 1895h: 24 (w.) SOUTH AFRICA. Combination in M. (Xeromyrmex): Wheeler, W.M. 1922a: 872. Raised to species: Bolton, 1987: 336.