Proceratium lunatum Terron, 1981

Hita Garcia, Francisco, Hawkes, Peter G. & Alpert, Gary D., 2014, Taxonomy of the ant genus Proceratium Roger (Hymenoptera, Formicidae) in the Afrotropical region with a revision of the P. arnoldi clade and description of four new species, ZooKeys 447, pp. 47-86 : 59

Taxon classification Animalia Hymenoptera Formicidae

Proceratium lunatum Terron, 1981 Figs 3F, 5B, 5E, 6C, 8C, 8D, 14A, 14B, 14C, 18

Proceratium lunatum Terron, 1981: 96. [see also Baroni Urbani and de Andrade 2003: 290]

Type material.

Holotype, pinned worker, CAMEROON, Arboretum de Mbalmayo (51 km S of Yaounde), no. 1579, 17.III.1968, (G. Terron) (CIRAD). Paratypes, one pinned paratype worker from CAMEROON, Kala (18 km W Yaounde), Ve Berlese, sp. 1, tamisage terre et terreau, 16.V.1974, (G. Terron) (CIRAD); two pinned paratype workers from CAMEROON, Mbalmayo, no. 1759, 17.III.1968 (G. Terron) (BMNH: CASENT0902426; MNHN); one pinned paratype worker from CAMEROON, UO Bikok, tamisage terre et terreau, 19.III.1974, (G. Terron) (MHNG: CASENT0914221).

Non-type material.

CAMEROON: Sud-Ouest, Korup N. P., 6.9 km 317°NW Mundemba, 5.016 N, 8.864 E, 110 m, rainforest, 19.IV.2000 (B.L. Fisher) (CASC: CASENT0005926); GABON: Woleu-Ntem, 31.3 km 108°ESE Minvoul, 2.08N, 12.40667E, 600 m, rainforest, 11.II.1998 (B.L. Fisher) (CASC: CASENT0914280); UGANDA: Western Uganda, Kabarole, Kibale National Park, Kanyawara Biological Station, 0.56437N, 30.36059E, 1520 m, moist evergreen forest, 8.-11.VIII.2012 (B.L. Fisher et al.) (CASC: CASENT0355483).

Diagnosis.

The following character combination distinguishes Proceratium lunatum from the other Afrotropical members of the Proceratium arnoldi clade: eyes strongly reduced (OI 3-5), usually consisting of a single ommatidium, rarely more; head slightly longer than broad (CI 92-95); maculae on vertexal angles of head well developed and conspicuous; mesopleurae weakly to moderately inflated posteriorly; petiolar node high nodiform, anteroposteriorly compressed, with anterior face relatively straight; petiole in dorsal view between 1.2 to 1.3 times wider than long DPeI 122-129; ventral process of petiole lamelliform and approximately rectangular, lamella not significantly pointing anteriorly nor posteriorly; abdominal segment IV between 1.0 to 1.2 times longer than abdominal segment III (ASI 104-118); head, mesosoma and petiole with mat of short decumbent to subdecumbent pubescence only, without any longer, fine suberect to erect hairs.

Worker measurements

(N=8). TL 2.81-3.43; EL 0.02-0.04; SL 0.46-0.60; HL 0.73-0.84; HLM 0.86-0.96; HW 0.68-077; WL 0.84-1.00; HFeL 0.52-0.63; HTiL 0.41-0.51; HBaL 0.31-0.42; PeL 0.27-0.30; PeW 0.35-0.38; DPeI 122-129; LT3 0.40-0.57; LS4 0.14-0.23; LT4 0.43-0.60; OI 3-5; CI 92-95; SI 63-71; IGR 0.33-0.38; ASI 104-118.

Worker description.

In full-face view head slightly longer than broad (CI 92-95), sides weakly convex, vertex flat to weakly convex. Clypeus medially reduced, its anterior margin subconvex to slightly triangular, only slightly protruding anteriorly, not surrounding the antennal sockets and not medially impressed, antennal socket with broad torulus. Frontal carinae relatively short and widely separated, not converging medially and strongly diverging posteriorly, partially covering antennal insertions; frontal carinae conspicuously raised on their anterior half, much less posteriorly. Eyes very small, consisting one to three or four weak ommatidia (OI 3-5) and located on mid line of head. Mandibles elongate-triangular; masticatory margin of mandibles with four relatively small teeth/denticles, decreasing in size from larger apical tooth to basal denticle. Mesosoma in profile convex and approximately as long as the maximum head length including mandibles. Lower mesopleurae with well impressed sutures, no other sutures developed on lateral or dorsal mesosoma; mesopleurae weakly to moderately inflated posteriorly; propodeum in profile armed with small, blunt teeth, propodeal lobes well developed, lamellate, rounded to subtriangular and blunt; declivitous face of propodeum between teeth and lobes noticeably concave; in posterodorsal view sides of propodeum separated from declivitous face by margin connecting propodeal lobes and propodeal teeth. Legs slender and elongate; pro- and mesotibiae with pectinate spurs; calcar of strigil without basal spine. Petiolar node in profile high, blocky nodiform, anterior face of petiole relatively straight, anterior and posterior faces approximately parallel, dorsum of node flat to weakly convex; petiole in dorsal view between 1.2 and 1.3 times wider than long (DPeI 122-129), petiolar node in dorsal view clearly much broader than long; ventral process of petiole lamelliform and approximately rectangular, lamella not significantly pointing anteriorly nor posteriorly. In dorsal view abdominal segment III anteriorly broader than petiole; its sides diverging posteriorly; dorsum of abdominal tergum III with posteromedial, very conspicuous, semitransparent, raised bulla below the integument; abdominal sternite III anteromedially with a marked subtriangular projection. Constriction between abdominal segment III and IV conspicuously impressed. Abdominal segment IV strongly recurved (IGR 0.33-0.38), conspicuously rounded on its curvature, especially posteriorly, abdominal tergum IV between 1.0 and 1.2 times longer than abdominal segment III (ASI 104-118); large, semitransparent and circular bulla situated posteromedially on abdominal tergum IV; remaining abdominal tergites and sternites relatively inconspicuous and curved ventrally. Whole body covered with dense mat of relatively short, decumbent to subdecumbent pubescence without abundant, much longer, suberect to erect, long, fine, standing hairs. Mandibles longitudinally rugose; most of body irregularly foveolate and/or granulate, sometimes more weakly developed on cephalic dorsum and anterior part of abdominal tergum IV, posteroventral part of abdominal tergum IV with conspicuous irregular rugosity; inflated, posterior part of mesopleura and declivitous face of propodeum unsculptured, smooth and shining. Head, mesosoma (excluding posteriorly inflated part of mesopleurae), postpetiole and remaining abdominal segments of light brown to brown colour, mandibles, inflated part of mesopleurae and legs always of lighter brown colour.

Distribution and ecology.

Proceratium lunatum is known to occur in Cameroon, Gabon and Uganda (Fig. 18) where it was collected in rainforests at elevations ranging from 110 to 1520 m. The known specimens were either collected from within the soil or sifted litter suggesting that Proceratium lunatum is a predominantly hypogaeic species.

Taxonomic notes.

The recognition of Proceratium lunatum within the Proceratium arnoldi clade is fairly easy and straightforward. The relatively broad head in full-face view (CI 92-95) groups it together with Proceratium burundense , Proceratium nilo , Proceratium sali and Proceratium sokoke (CI 91-95) while it separates it from Proceratium arnoldi and Proceratium carri that have thinner heads (CI 85-87). The lack of long, standing pilosity on top of a dense mat of much shorter pubescence distinguishes Proceratium lunatum from Proceratium carri , Proceratium nilo , Proceratium sali and Proceratium sokoke . The species closest to Proceratium lunatum seems to be Proceratium burundense . However, both differ in eye size, ventral process of the petiole, and propodeal armament. Proceratium lunatum has smaller eyes (OI 3-5) and shorter propodeal teeth than Proceratium burundense (OI 8). In addition, the ventral process of the petiole has a very distinct posteroventral corner that strongly projects ventrally, whereas the process of Proceratium lunatum is more or less rectangular without a projecting posteroventral corner.

Variation.

The Proceratium lunatum material from Cameroon and Gabon shows no observable intraspecific variation. The specimen from Uganda, however, displays some noticeable differences. It possesses longer antennal scapes (SI 71 vs. SI 63-66) and is generally larger than the western specimens (TL 3.43 vs. TL 2.81-2.94). Nevertheless, we consider these differences as intraspecific variation. The difference in body size is well within the range of other species, thus not significant, and the longer antennal scape alone is not sufficient to warrant species status. This assessment might change with further material from the eastern parts of the equatorial forest belt, such as Uganda, Rwanda and Kenya, but for the moment we keep all the material listed here as Proceratium lunatum as one species.