Polyrhachis retusa

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

Polyrhachis retusa P.png

Polyrhachis retusa D.png

Known only from the holotype.

Identification

Kohout (2007) - P. retusa is relatively close to Polyrhachis porcata, however, they differ in a number of characters, including their relative size (HL 1.12 in retusa versus 1.50-1.68 in porcata). The pronotal dorsum in lateral view is much less convex in retusa with the pronotal teeth short and broad-based and the petiole is narrow in profile with its dorsal margin distinctly acute. The first gastral segment of retusa is concave, but its dorsal margin is not elevated dorsally. In contrast, the pronotal dorsum in porcata is distinctly convex in lateral view with the humeri armed with laterally and anteriorly directed, acute spines. The petiole, in lateral view, is scale-like, with both faces distinctly convex and the dorsal margin less acute. The first gastral segment is concave with the dorsal margin of the concavity produced above the face of the segment.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

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

Check distribution from AntMaps.

Distribution based on specimens

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The above specimen data are provided by AntWeb. Please see Polyrhachis retusa 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.

  • retusa. Polyrhachis (Aulacomyrma) retusa Kohout, 2007a: 235, figs. 93, 96, 99 (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

holotype: TL c. 4.43; HL 1.12; HW 1.04; CI 93; SL 1.22; SI 117; PW 0.87; MTL 1.12.

Clypeus with anterior margin arcuate, weakly truncate; in profile clypeus straight anteriorly with outline raised towards basal margin due to a short carina formed by median stria; basal margin impressed medially, laterally indicated by break in cephalic sculpture. Frontal triangle indistinct. Frontal carinae with raised laminate lobes. Sides of head in front of eyes converging anteriorly towards mandibular bases; posteriorly rounding into weakly convex preoccipital margin. Eyes strongly convex, clearly breaking cephalic outline in full face view. Pronotal humeri armed with acute, broad-based teeth, lateral margins curving from bases onto sides, pronotal dorsum immarginate. Promesonotal suture distinct. Metanotal groove lacking. Lateral margin of mesonotal dorsum formed by outermost dorsal striae. Propodeum immarginate laterally and posteriorly with dorsum descending into declivity in uninterrupted curve. Dorsal margin of petiole with shallow emargination medially, weakly jagged laterally, lateral spines relatively long, curved outwards, backwards and upwards. Anterior face of first gastral segment concave, with dorsal margin of concavity acute, not elevated above dorsal face of segment.

Sculpture of head and body consisting of more-or-less regularly spaced striae; mostly longitudinal on dorsum of head, those on vertex curving medially towards frontal carinae and central area. Pronotal striation distinctly converging anteriorly, several median striae curving tranversely onto pronotal collar. Mesonotal-propodeal dorsum with striae V-shaped, converging posteriorly and terminating just before propodeal dorsum descends into declivity. Petiole with anterior face wrinkled, transversely at base of segment and vertically on sides; posterior face of petiole finely shagreened. First gastral segment distinctly striate laterally, striae less distinct dorsally and becoming reticulate-punctate centrally.

Head and mesosoma with numerous, yellow, erect hairs, notably on front of head; distinctly shorter hairs arising from vertex and mesosomal dorsum. Petiole with a few short, erect hairs on dorsal margin. First gastral segment with a few, short, posteriorly directed hairs, more erect and distinctly longer on apex and venter. Very sparse, pale yellow, appressed pubescence on dorsum of head, mesosoma and gastral dorsum.

Black, including antennal scapes, femora and proximal ends of hind tibiae. Funiculi, except apices and basal tarsal segments medium to dark reddish-brown. Tibiae, except their proximal ends, apical segments of tarsi and last funicular segments distinctly light reddish-brown.

Type Material

HOLOTYPE: INDONESIA, IRIAN JAYA (New Guinea: Neth. on data label), Vogelkop, Fak Fak, S. coast of Bomberai Pen., 02º55’S, 132º18’E, 10-100m, 3.vi.1959, T. C. Maa (worker). Type distribution: unique holotype in Museum of Comparative Zoology.

Etymology

From the Latin word retusus, meaning blunted, rounded, refering to the bluntly terminated propodeal dorsum of this species.

References