Trachymyrmex atlanticus, Mayhé-Nunes, Antonio J. & Brandão, Roberto F., 2007

Mayhé-Nunes, Antonio J. & Brandão, Roberto F., 2007, Revisionary studies on the attine ant genus Trachymyrmex Forel. Part 3: The Jamaicensis group (Hymenoptera: Formicidae), Zootaxa 1444, pp. 1-21 : 5-6

Trachymyrmex atlanticus new species

( Figs. 1–4 , 30)

Worker measurements (n = 9). TL 5.2 (4.3–5.6); DHL 1.51 (1.31–1.58); HW 1.39 (1.11–1.47); IFW 0.89 (0.78–0.93); ScL 1.14 (1.00–1.24); HWL 0.95 (0.71–1.09); MeL 2.02 (1.78–2.13); PL 0.37 (0.27–0.42); PPL 0.49 (0.40–0.56); GL 1.37 (1.18–1.44); HfL 2.14 (1.78–2.22).

Worker description: Light yellow to yellowish-brown, with darker spots on the head dorsum, mesosoma and gaster, giving to overall body a smudge appearance in lighter specimens; darker funiculus, tarsi and shiny mandibles. Integument opaque and finely granulose. Pilosity: short, bristly spatulate dark hairs confined to body projections, strongly curved or hook-like hairs on other parts of the body.

Head in full face view ( Fig. 1 ) a little longer than broad to as long as broad (DCI average 93; 90–99). Outer border of mandible feebly sinuous; masticatory margin with two apical and five teeth, with a diastema between the subapical and third teeth. Clypeus median apron without projections. Frontal area impressed. Frontal lobe semicircular, moderately expanded (FLI average 63; 62–67), with smooth free border, lacking prominent denticles on the slightly crenulate antero-lateral border. Frontal carina moderately diverging caudad, reaching the antennal scrobe posterior end in a small tooth at the posterior margin of head; preocular carina posteriorly ending in the posterior margin as a tubercle larger than the frontal carina projection. Occipital spine almost as long as preocular carina projection. Supraocular projection indistinct. Inferior corner of occiput, in side view, with a small blunt spine. Eye faintly convex, not surpassing the head lateral border, with 14 facets in a row across the greatest diameter. Antennal scape, when lodged in the scrobe, projecting beyond the tip of the preocular carina projection; gradually thickened toward apex, covered with small piligerous tubercles.

Mesosoma ( Figs. 1, 2 ). Pronotal dorsum faintly marginate in front and on sides; antero-inferior corner with a strong and blunt flattened spine; inferior margin smooth; median pronotal tooth tip truncate, projected above the tip of the longer lateral pronotal spines, which points outwards from the pronotum, in frontal view. Anterior pair of mesonotal spines a little longer and stouter than lateral pronotal ones, directed upwards; the second and third pairs gradually smaller, almost tooth-like. Anterior margin of katepisternum smooth, with a minute tooth on the superior third. Metanotal constriction shallowly impressed. Basal face of propodeum laterally marginate by a row of 3–4 denticles on each side; propodeal spines shorter than the distance between their inner bases. Hind femora longer than mesosoma length.

Waist and gaster ( Figs. 2–4 ). Dorsum of petiolar node with two pairs of minute spines, the sides parallel in dorsal view, with a series of lateral denticles; sternum without sagital keel. Postpetiole broader than long in dorsal view, broader behind than in front, and shallowly impressed dorsally, with concave postero-dorsal bor- der. Gaster, when seen from above, suboval. Tergum I (=abdominal tergum IV) with straight lateral faces separated from the dorsal face by a longitudinal row of piligerous tubercles on each side; anterior two thirds of dorsum with three glabrous shallow longitudinal furrows separated by a pair of piligerous tubercles rows. Sternum I with a small anterior sagital keel.

Gyne and male: Unknown.

Holotype worker: BRAZIL, Rio de Janeiro: Restinga da Marambaia [23o 02’ S, 43o 36’ W], 15.iii.2005, A.B. Vargas col., pitfall trap # P2G3S16 (deposited in CECL).

Paratype workers: same data as holotype, pitfalls # P2G3S16 (2 workers deposited in CECL, 3 deposited in MZSP), 2 workers # P3G2S6 (deposited in CECL), 2 workers # P2G2S14 (deposited in MZSP).

Etymology: This species shows a distribution restricted to the Atlantic forest domain (Fig. 30), and hence its name.

Material examined: BRAZIL, Bahia: Ilhéus, Fazenda Comodoty, 03.xii.1991, A.M.V. Encarnação leg., 5 workers ( CPDC), 3 workers ( MZSP); Teixeira de Freitas, 10.xii.1992, [col. unknown], in Eucalyptus plantation, 2 workers ( CECL; MZSP). Espírito Santo: Itaúnas, 23.vii.1989, J. Diniz col. 2 workers ( CECL; MZSP). Rio de Janeiro: Ilha da Marambaia, Praia Grande, 20.ix.1985, R. Xerez col. 1 worker ( CECL); Restinga da Marambaia, [no date], P. S. Meneguete col. 1 worker ( CECL).

Comments. Workers of this species may be confounded with those of T. zeteki , but can be separated because T. atlanticus workers lack conspicuous teeth on the anterior lateral margin of the frontal lobes, and also by the longer antennal scapes, shorter propodeal spines, sagital keel on sternum I of gaster and lighter color. They differ from T. jamaicensis and T. ixyodus by the projecting midpronotal tooth, which bears much shorter anterior mesonotal projections. From T. haytianus workers of T. atlanticus can be distinguished by coarse spatulate hairs all over the body and the lighter coloration. Trachymyrmex isthmicus lacks the inferior pronotal projection and has the lateral pronotal projections shorter than mesonotal anterior ones.

This is the most common Trachymyrmex in the Restinga da Marambaia. We base our description on a series captured in pitfall traps, but we were not able to find their nests. Samples from other localities were also exclusively collected near the beach at the Brazilian coast, but unfortunately the labels do not contain further biological data. Workers of T. atlanticus may build their nests in sandy soils in the coastal dunes.

Figures

FIGURES 1 – 4. Scanning electron micrograph of Trachymyrmex atlanticus, paratype worker from Brazil, RJ: Restinga da Marambaia. 1. Head in frontal view; scale bar = 500 μm. 2. Mesosoma and waist in lateral view; scale bar = 500 μm. 3. Waist in lateral view (detail); scale bar = 125 μm. 4. Postpetiole and gaster in dorsal view; scale bar = 250 μm.