Polyrhachis abdita

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Polyrhachis abdita
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Camponotini
Genus: Polyrhachis
Subgenus: Aulacomyrma
Species: P. abdita
Binomial name
Polyrhachis abdita
Kohout, 2007

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Specimen labels

Presently known from the Lelet Plateau on the island of New Ireland.

Identification

Kohout (2007) - P. abdita is very similar to Polyrhachis dohrni, but can be distinquished by the characters listed under the latter. Of these, the most important are the more flattened eyes and complete absence of an anterodorsal process on the first gastral segment in abdita. Because of their similarity and adjoining distributions, abdita could be considered a higher altitude population of dohrni. However, with most of the distinguishing characters constant and no intermediate forms detected, I believe they represent distinct species.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Indo-Australian Region: New Guinea (type locality).

Distribution based on specimens

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The above specimen data are provided by AntWeb. Please see Polyrhachis abdita for further details

Biology

The subgenus this species is a member of, Aulacomyrma, is poorly colected. Kohout (2007) summarized what is known about their biology in a revision of the species in the subgenus. This offers an explanation as to why most Aulacomyrma are known from few collections and specimens. There are only two records of nests being found. A small colony of Polyrhachis dohrni was collected by Kohout from a dry hollow twig on a living tree at the edge of lowland rainforest. The internal walls of the twig cavity were lined with a little silk. Ward collected a nest of Polyrhachis wardi from a dry twig of a rainforest tree. The colonies of both species were rather small, with only a few workers (5 and 11 respectively, including 2 and 3 alate queens and a single male). If such a nesting pattern is the norm for other species of the subgenus, that might explain the general scarcity of Aulacomyrma material even in the best collections. Many Aulacomyrma species are described and only known from a holotype.

Castes

Known only from the worker caste.

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • abdita. Polyrhachis (Aulacomyrma) abdita Kohout, 2007a: 195, figs. 1, 4, 7 (w.) NEW GUINEA.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

Worker

TL c. 4.64-5.44 (5.19); HL 1.15-1.37 (1.31); HW 1.03-1.22 (1.18); CI 88-90 (90); SL 1.22-1.40 (1.40); SI 114-119 (119); PW 1.00-1.18 (1.18); MTL 1.28, 1.09-1.34 (1.28) (13 measured).

Anterior clypeal margin arcuate with shallow emargination medially; in profile clypeus virtually straight with very weakly impressed basal margin, indicated laterally by a faint line that barely breaks cephalic sculpture. Frontal carinae sinuate, with laminate lobes. Sides of head very weakly convex, almost straight in front of eyes before converging towards bases of mandibles. Eyes rather flat, with anterior margins somewhat sunk into shallow depressions in cephalic sculpture; in full face view almost level with, but failing to break lateral cephalic outline. Mesosoma marginate along entire length. Pronotal humeri armed with broad-based, angulate, acute teeth, that are laterally continuous with pronotal margin. Dorsum of pronotum widest at midlength. Promesonotal suture distinct; metanotal groove lacking dorsally, position marked by shallow emarginations in lateral margin. Propodeum with lateral margins only narrowly rounded posteriorly; dorsum descending into virtually vertical declivity in an unobstructed curve. Petiole with sharp dorsal margin, its apex higher than anterodorsal margin of first gastral segment; lateral petiolar spines directed outwards and slightly curved backwards from bases. First gastral segment concave medially, accomodating posterior face of petiole; anterodorsal margin of concavity rather blunt, not elevated above dorsal face of segment.

Mandibles finely, mostly longitudinally, striate-rugose, with shallow pits towards masticatory border. Sculpture of body consisting of more-or-less regularly spaced striae, that are mostly longitudinal on head, distinctly anteriorly converging on pronotal dorsum and posteriorly converging on mesonotal-propodeal dorsum; striae oblique on sides of mesosoma and longitudinal on sides of gaster. Petiole and dorsum of gaster finely, microscopically, shagreened.

Entire body with numerous semierect to erect, off-white to silvery hairs, that do not exceed greatest diameter of eye in length. Silvery to silvery-grey appressed pubescence fairly abundant, partly concealing underlying sculpture, notably on propodeal dorsum, where it curves towards midline. Gastral pubescence rather abundant, silvery at sides and along posterior margins of segments; becoming distinctly silvery-grey on dorsal surface of first gastral segment.

Black; mandibular masticatory border, apices of antennal scapes, funiculi, femora and tarsi medium to dark reddish brown, with funiculi and tarsi becoming lighter apically. Tibiae distinctly lighter, except their proximal and distal ends, which are very narrowly dark, reddish brown.

Type Material

HOLOTYPE: PAPUA NEW GUINEA, New Ireland Prov., Lelet Plateau, c. 03º20’S, 151º56’E, 800-1000m, 19-24.vii.1984, R. J. Kohout acc. 84.95 (worker). PARATYPES: data as for holotype (12 workers). Type distribution: holotype and 2 paratypes in Australian National Insect Collection; 2 paratypes each in The Natural History Museum, California Academy of Sciences, Los Angeles County Museum of Natural History, Museum of Comparative Zoology and Queensland Museum.

Etymology

Name derived from the Latin word abditus, meaning hidden, concealed.

References