Rhytidoponera arborea

This rainforest species is probably arboreal and forages on low vegetation and on the ground.

Identification
In comparison with other pulchella-group species having a dense mat of appressed pubescence on the gastric tergies, arborea is either larger (HW >1.10 in arborea, HW < 1.0 in pulchella and insularis) or differs in pilosity (depilis has little erect pilosity; terrestris is a little more setose than arborea). Rhytidoponera arborea and Rhytidoponera terrestris are rather similar, but the differences between them appear to be consistent. The occipital lobes are a little better developed in arborea (OLI 0.43-0.46 in arborea, 0.40-0.44 in terrestris) and not as far apart (OLD 0.62-0.66 in arborea, 0.66-0.71 in terrestris) (samples of 10 and 13 workers for arborea and terrestris, respectively). The scapes and femora of arborea have fewer standing hairs, as shown by the following ranges of setal counts (data on pulchella are included for comparison):

Finally, arborea and terrestris occur sympatrically (Col d' Amieu; vicinity of Col de Ho), and they are substituted for alternate alleles at three allozyme loci (amylase, esterase, and gluatamate oxaloacetate transaminase).

Distribution based on Regional Taxon Lists
Australasian Region: New Caledonia.

Biology
Rhytidoponera arborea has been collected in rainforest, from 40 to 450 m elevation, where workers were observed foraging on low foliage and on the ground. The present records suggest that this species may favor arboreal nesting sites; one colony was located in a cavity of a living rainforest tree, 10 m above the ground; another was nesting in an epiphytic fern (Asplenium) growing on a large boulder.

Nomenclature

 *  arborea. Rhytidoponera arborea Ward, 1984: 153, figs. 41, 42, 47, 48 (w.) NEW CALEDONIA.

Description
Type Material

Holotype worker. New Caledonia: Col d'Amieu Stn, 360 m,  20. ii. 1977, nest in cleft of rainforest tree, 10 m above ground (P.S. Ward acc. No. 2268) (ANIC Type No. 7580).

Paratype workers. A series of nidoparatype workers, same locality, date, and accession number (ANIC, BPBM, MBNH, MCZ, PSW).

Non-paratypic material. Additional material from 6 other localities which is considered to be conspecific is listed below (under Material Examined).

Measurements

Holotype worker. HW 1.31, WL 1.96, CI 0.93, MI 0.34, SI 0.97, SL12 0.20, SSC 9, FSC 0.

Paratype workes and other material. HW 1.14-1.32, WL 1.78-2.00, CI 0.86-).92, MI 0.30-0.40, SI 0.98-1.12, (n=20); SL12 0.18-0.21, SSC 7-10, FSC 0-2 (n = 9).

Diagnosis of Worker

Anterior clypeal margin obtusely angulate Frontal lobes expanded laterally and covering most of the antennal insertions; frontal carinae subparallel, converging to 85-90% of their maximum distance, the later (FCD) <1/2 the head width (FCI 0.41-0.46). Head quadrate, longer than wide, the sides weakly convex; occipital margin flat or very slightly concave, in full-face view. Eyes protruding slightly in dorsal view, OI 0.22-0.27. In lateral view, the frons rounds evenly into the vertex, the occipital lobes protruding slightly (OLI 0.43-0.46, OLD 0.62-0.66). Pronotum relatively slender, PI 0.76-0.82. Promesonotal suture distinct, obtusely V-shaped in dorsal view. Mesopropodeal impression indistinct; basal face of propodeum weakly differentiated from the declivitous face, the latter a little longer than the former, in lateral view. Inferior pronotal tooth well developed. Petiole as illustrated: node robust, somewhat rounded, with a short anterior peduncle (LPI 053-0.58; DNI 0.90-1.01; PN12 0.44-0.50); subpetiolar process consisting of a long, spiniform tooth (SL12 0.18-0.21; SPI 0.13-0.23).

Mandibles striate. Head predominantly rugose, the inter-rugal punctures smooth and shining.. Mesosoma and petiolar node rugose with interspaces shining, and with some rugulose sculpture on the sides; rugae tending to show a transverse orinetation on the propodeum. Abdominal tergite III with irregular, transverse striae, becoming rugostriate to rugulose anterolaterally. Abdominal tergite IV with weak, transverse, striolate-imbricate parts of the body. Standing hairs sparse on the upper surface of the femora (FSC 0-2; HSC 0-6, nearly always on the apical half). Abdominal tergites III and IV with a distinct mat of appressed pubescence. Black, with dark brown mandibles, antennae, and legs; the apical funicular and tarsal segments a lighter, ferrugineous brown.