Rhytidoponera mimica

Rhytidoponera mimica is a striking orange and black ant that is an apparent Mullerian mimic of Camponotus irritans croceomaculatus. Both forage on low vegetation.

Identification
Workers of Rhytidoponera mimica have a unique and divergent coloration pattern among the New Caledonian Rhytidoponera. The conspicuous orange and black pattern is shared with workers of a sympatric foliage-foraging Camponotus irritans croceomaculatus Emery. This may be a case of Mullerian, rather than Batesian, mimicry since: 1) Rhytidoponera workers can inflict a painful sting; 2) elsewhere in New Caledonia, Rhytidoponera species with a conspicuous shiny gaster, such as Rhytidoponera versicolor, appear to be mimicked by various foliage-frequenting arthropods.

Coloration aside, Rhytidoponera mimica may be distinguished from other congeners by the combination of small size (HW < 0.95 mm), absence of erect pilosity from the propodeum and upper surfaces of the femora, and absence of dense pubescence on the shiny gastric tergites.

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

Biology
Rhytidoponera mimica was collected in a small patch of gully rainforest, 300 meters elevation, surrounded by niaouli (Melaleuca scrub). Workers were foraging on low vegetation. Two nests were located, both in vertical banks of soil beside a stream.

Castes
Known only from workers.

Nomenclature

 *  mimica. Rhytidoponera mimica Ward, 1984: 163, figs. 67, 68, 73, 74 (w.) NEW CALEDONIA.

Description
Type Material

Holotype worker. New Caledonia: Col d'Amoss, 300 m.  3.v.1980, foraging on low vegetation, gully rainfores (P.S. Ward acc. No. 4215-1) (ANIC Type No. 7586).

Paratype workers. A series of 3 accessions from the type locality, same date (P.S. Ward acc. Nos 4215-1, 4216, 4217) (ANIC,BPBM, BMNH, MCZC, MNHN, PSW).

Measurements

Holotype worker. HW 0.9, WL 1.34, CI 0.88, MI 0.40, SI 1.06, SL12 0.18, SSC 0, FSC 0. Paratype workers (n = 9) HW 0.86 - 0.92, WL 1.22 - 1.34, CI 0.87 - 0.90, MI 0.36 - 0.44, SI 0.99 - 1.07, SL12 0.15 - 0.18, SSC 0-1, FSC 0.

Diagnosis of Worker

Similar to Rhytidoponera insularis in relative body dimensions and sculpture. Anterior clypeal margin more sharply angulate. Petiole with a relatively high, narrow node (LPI 0.45 - 0.49; DNI 0.86 - 0.90; PN12 0.39 - 0.43), and with a conspicuous anterior peduncle and a slender, spine-like subpetiolar process (SPI 0.13 - 0.18). Head rugose to longitudinally rugostriate, the inter-rugal spaces shining. Mesosoma rugose to transversely rugostriate, the rugae weak and interspaces smooth and shining. Anepisternum largely smooth and shining, and devoid of sculpture centrally except for 2 or 3 punctures. Abdominal tergites III and IV shining, with weak striolate sculpture which is posteromedially obsolete. Gastric tergites with appressed hairs moderately dense, separated by about their lengths. Eerect setae relatively sparse on most parts of the body, generally lacking on the propodeum and upper surfaces of the scapes and femora. Mesosoma and petiole dark brown to black; head a contrasting light ferrugineous brown; gaster, legs (including coxae) and mandibles a paler luteous brown, contrasting strongly with the mesosoma.