Stenamma africanum

Identification
Rigato (2011) - Stenamma africanum is a relatively large species with elongate scapes and with a posterior clypeal lobe often as narrow as in some Stenamma westwoodii specimens. The petiolar sternite is shallowly, but distinctly, concave below the node.

S. africanum worker shares most features with Stenamma sardoum and S. westwoodii; but it has longer scapes, almost reaching the occipital border when laid back.

Distribution based on Regional Taxon Lists
Palaearctic Region: Algeria, Tunisia.

Nomenclature

 *  africanum. Stenamma africanum Santschi, 1939d: 66, fig. 2 (w.q.) TUNISIA. Cagniant, 1971: 98 (m.). Junior synonym of msilanum: DuBois, 1998b: 254. Revived from synonymy: Rigato, 2011: 16. Senior synonym of submuticum: Rigato, 2011: 16.
 * submuticum. Stenamma africanum var. submuticum Santschi, 1939d: 67, fig. 3 (w.) ALGERIA. Junior synonym of msilanum: DuBois, 1998b: 254. Junior synonym of africanum: Rigato, 2011: 16.

Rigato (2011) - While examining Stenamma siculum a comparison was made with its apparently closest relative, Stenamma msilanum  (sensu DuBois, 1998, who considered africanum to be a junior synonym of msilanum) and  S. africanum type series, which consists of a few workers and one gyne, was borrowed  from NHMB. Workers come from several Tunisian localities and one specimen is from Bone (currently Annaba), a coastal locality of Northeast Algeria, not far from Tunisia. All workers appear consistent and I consider them as conspecific and also conspecific with the type of S. africanum var. submuticum Santschi, which was also examined. The measurements given by DuBois for the lectotype he designated are misleading. He gave a SI of 115, which is considerably higher than any other species dealt with in this paper. Such an index would mean a scape strongly surpassing the posterior margin of the head when laid back, even exceeding that of Stenamma petiolatum. However, on examination the lectotype turned out as quite ordinary with SI = 95 and scape’s apex closely approaching the posterior margin of the head when laid back. Paralectotypes have a slightly higher SI as also does a separate series from Tunisia that I examined. Other features of S. africanum worker are the relatively low postpetiole, looking longer than high (PPL>PPH), and the shallow, but easily visible, concavity of petiolar sternite in profile at the level of the node. The gyne of S. africanum in the type series comes from “Col de Talmetz”. Although both Santschi (1939) and DuBois (1998, as “Col de Talmet”) reported this as a Tunisian locality, I found it to be in North Algeria (ca. 36°41’ N and 4°43’ E), and quite distant from where S. africanum workers were collected. However, I consider that the gyne is conspecific with the workers, even though it has SI = 91, and a less concave petiolar sternite.

Finally, I examined the holotype of S. msilanum. It was described from a single gyne collected in the forest of Msila (Oran prov., Algeria), which is relatively close to Morocco. In my opinion it is not conspecific with S. africanum. The most striking differences lie in colour and petiolar shape. The S. msilanum type is as dark as S. debile gynes (S. africanum is ferrugineous), and its waist’s sternites are fully straight in profile.

Consequently, I propose to formally resurrect S. africanum as a valid species, with submuticum as its junior synonym, different from S. msilanum.

Cagniant (1971) described the male of S. africanum. His diagnosis, drawings and description look comparable to those of S. siculum, which has more sculptured propodeal dorsum and standing hairs on scapes. The propodeum is smoother in North African specimens from Algeria and Morocco (Cagniant l.c. and pers. comm.): ≪propodeum: sur les côtés quelques rides longitudinales et sinueuses se détachant mal de la forte réticulation de base; sur le dessus: réticulé sans rides, la réticulation devenant superfi cielles et même disparaissant presque dans la zone médiane; face postérieure: luisante, avec 2 ébauches de rides transverses≫. Unfortunately, I could not see Cagniant’s males and associated females. Because knowledge of North African Stenamma is still incomplete, I remain unsure about the identity of his specimens.

Worker
Rigato (2011) - Lectotype. TL 4.1; HL 0.92; HW 0.77; CI 84; SL 0.73; SI 95; PCI 28; PnW 0.53; AL 1.12; PSI 1.65; PeL 0.40; PPL 0.25; PeH 0.21; PPH 0.20; PeW 0.15; PPW 0.21; PI1 62; PI2 52; MTL 0.63; TI 82.

Including paralectotypes: TL 3.5–4.1; HL 0.86–0.95; HW 0.69–0.78; CI 80–84; SL 0.68–0.76; SI 95–100; PCI 23–31; PnW 0.47–0.54; AL 1.00–1.13; PSI 1.2–1.7; PeL 0.37–0.43; PPL 0.23–0.26; PeH 0.20–0.24; PPH 0.20–0.23; PeW 0.14–0.17; PPW 0.20–0.23; PI1 56–65; PI2 51–60; MTL 0.59–0.67; TI 83–92 (11 measured).

Queen
Rigato (2011) - TL 4.9; HL 1.02; HW 0.87; CI 85; SL 0.79; SI 91; PCI 32; AL 1.48; PSI 1.57; ScW 0.75; MnL 1.11; PeL 0.54; PPL 0.27; PeH 0.27; PPH 0.29; PeW 0.21; PPW 0.28; PI1 50; PI2 62; MTL 0.74; TI 85 (1 measured).

Type Material
Rigato (2011) - Lectotype worker, paralectotype workers and gyne, TUNISIA: Ain-Draham (Normand)  [Lectotype]; Camp  de  la  Sante (Normand); Camp  de  Bugeaud  (Normand); ALGERIA: Col de Talmetz, 11.x.1928 (Normand)  [examined].

References based on Global Ant Biodiversity Informatics

 * Borowiec L. 2014. Catalogue of ants of Europe, the Mediterranean Basin and adjacent regions (Hymenoptera: Formicidae). Genus (Wroclaw) 25(1-2): 1-340.
 * Cagniant, H. Les peuplements de fourmis des forêts algériennes: écologie, biocénotique, essai biologique. Universite de Toulouse, 1973.
 * Rigato F. 2011. Contributions to the taxonomy of West European and North African Stenamma of the westwoodii species-group. (Hymenoptera Formicidae). Memorie della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano 37: 1-56.