Nesomyrmex angulatus ( Mayr 1862 )

Garcia, Francisco Hita, Mbanyana, Nokuthula, Audisio, Tracy Lynn & Alpert, Gary D., 2017, Taxonomy of the ant genus Nesomyrmex Wheeler (Formicidae, Myrmicinae) in the Afrotropical region, with a review of current species groups and description of a new species of the N. angulatus group from Mozambique, European Journal of Taxonomy 258, pp. 1-31 : 15-17

Nesomyrmex angulatus ( Mayr 1862)

Figs 3 C–D, 4B, 8A, 9A, 14

Leptothorax angulatus Mayr, 1862: 739 (w.), Egypt.

Leptothorax angulatus var. concolor Santschi, 1914: 107 , fig. 15 (w.), Kenya.

Leptothorax angulatus r. ilgii Forel, 1894: 82 (w.), Ethiopia.

Leptothorax latinodis Mayr, 1895: 130 (w.), Mozambique.

Leptothorax angulatus – Santschi 1914: 107 (q.).

Leptothorax (Goniothorax) angulatus – Emery 1896: 58 (footnote).

Nesomyrmex angulatus – Bolton 2003: 272. See also: Mbanyana & Robertson 2008: 38 . (Current subspecies: nominal plus lybica.)

Leptothorax (Goniothorax) angulatus r. ilgii – Santschi 1912: 148 (q.). — W.M. Wheeler 1922: 891. (Junior synonym of angulatus : Bolton 1982: 324.)

Leptothorax (Goniothorax) latinodis – Emery 1896: 58 (footnote). (Junior synonym of angulatus : Bolton 1982: 324.)

Leptothorax angulatus var. concolor – Emery 1915: 16 (q.m.). (Junior synonym of angulatus : Bolton 1982: 324.)

Diagnosis

The following character combination distinguishes N. angulatus from the other members of the group: in profile mesosomal dorsum forming a single, uninterrupted flat surface without any trace of metanotal groove; petiolar peduncle short; body colour yellow to very light brown.

Diagnostic comments

Nesomyrmex angulatus together with N. grisoni are easily separable from the other members of the group on the basis of the dorsal mesosomal outline, which is an uninterrupted, flat surface without any trace of a metanotal groove. The separation of N. angulatus from N. grisoni is less clear though. As Bolton (1982) stated in his revision, the only differentiating character is body colour, which is yellowish in N. angulatus and dark brown to black in N. grisoni . In general, body coloration is a rather weak diagnostic character and extremely variable in many ant species, and it is likely that both species are actually conspecific and the differently coloured forms represent geographic or ecological variants. The latter seems probable if one considers that N. angulatus is predominantly an arid-adapted species, while N. grisoni appears to prefer humid rain forests. Nevertheless, at the moment we hesitate to synonymise the two species and prefer to keep them separate for the following reasons. First, while there is a lot of material of N. angulatus in many museums, there is not much of N. grisoni , making comparative analyses challenging. Secondly, and more importantly, we are not fully convinced that all the material currently listed and identified as N. angulatus represents the same species. On the basis of some recent collections from Kenya and Mozambique we were able to observe a lot of morphological variation within and between localities. As already noted by Bolton (1982), the shape of the petiolar node seems to be especially variable. Consequently, we cannot rule out the possibility of dealing with a complex of more or less cryptic species. At the same time it is possible that N. angulatus is not only a very successful and widespread, but also an extremely variable species. The solution to this problem is not the aim of this study, since it requires the accumulation of an extensive amount of material from all over Africa, the Arabian Peninsula, and the Malagasy region.

Biology

Nesomyrmex angulatus was collected from a variety of habitat types, such as tropical dry forest, coastal scrub, mangrove forest, savannah, and Acacia woodland. In general it seems as if the species prefers comparatively arid environments. In addition, it is predominantly found on the trunk of trees or the lower vegetation, rarely on the ground, and it nests in pre-existing cavities of dead wood ( Bolton 1982; Mbanyana & Robertson 2008).

Distribution

This species has by far the widest distribution range within the N. angulatus group, and likely represents the most widespread Nesomyrmex species on a global scale. It is found in the majority of African countries, as well as on the Arabian Peninsula and in most of the Malagasy region.

Figures

Fig. 3. Anterior cephalic dorsum (white ellipse around anterior clypeus) and body in profile. A–B. N. humerosus (Emery, 1896) (CASENT0906196). C. N. angulatus (Mayr, 1862) (CASENT 0235552). D. N. angulatus (Mayr, 1862) (CASENT0922010).