Polyrhachis exarata

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Polyrhachis exarata
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Camponotini
Genus: Polyrhachis
Subgenus: Aulacomyrma
Species: P. exarata
Binomial name
Polyrhachis exarata
Emery, 1887

Polyrhachis exarata casent0009233 profile 1.jpg

Polyrhachis exarata casent0009233 dorsal 1.jpg

Specimen labels

Nothing is known about the biology of Polyrhachis exarata.

Identification

Kohout (2007) - In general appearance, P. exarata resembles Polyrhachis parva. They share rather strong, broad-based pronotal teeth that are somewhat weakly emarginate at their bases; a distinct, weakly inward bowed, transverse ridge separating the propodeal dorsum from the declivity and an almost identical color scheme. However, they differ in several characters, including the longitudinal striation of the pronotal dorsum. In P. exarata the striation is parallel with the pronotal margins, while in parva the striae distinctly converge anteriorly. The propodeal margins in exarata terminate in narrowly rounded processes that are weakly widened before rounding into the posterior margin. In contrast, the propodeal margins in parva terminate in minute blunt angles. The anterior face of first gastral segment is medially concave in exarata with the anterodorsal margin of the concavity bluntly rounding onto the dorsum of the segment. In parva the concavity is strongly and acutely marginate, with its anterodorsal margin produced dorso-medially and raised above the dorsal face of the gaster.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

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

Distribution based on specimens

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

  • exarata. Polyrhachis exarata Emery, 1887a: 226 (w.) INDONESIA (Misool I.). Combination in P. (Aulacomyrma): Emery, 1921e: 17. See also: Kohout, 2007a: 198.

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

Description

Worker

Kohout (2007) - Holotype: TL c. 4.84; HL 1.18; HW 1.06; CI 90; SL 1.31; SI 123; PW 1.00 ; MTL 1.21.

Clypeus with anterior margin shallowly truncate in middle; median longitudinal carina distinct. Sides of head in front of eyes only weakly convex. Eyes convex, in full face view clearly breaking lateral cephalic outline. Mesosoma marginate along entire length. Pronotal humeri with rather strong, forward directed, broad-based teeth; propodeal margins terminating posteriorly in short, rounded processes, that appear in profile as minute, weakly upturned teeth. Propodeal dorsum separated from declivity by a distinct, slightly inward bowed, transverse ridge. Petiole with dorsal margin sharp, somewhat sinuate in dorsal view; lateral spines acute, bent outwards and backwards. First gastral segment only shallowly concave; dorso-medial margin of concavity blunt, not raised above dorsal face of segment.

Dorsum of head and pronotum with shiny, regularly spaced, striae, longitudinal on pronotum and posteriorly converging towards midline on mesonotal-propodeal dorsum. Petiole with both faces finely shagreened. Sides of first gastral segment distinctly, longitudinally striate with sculpture becoming more reticulate-puncate on dorsum.

Mandibles and sides of head with a few short semi-erect to erect hairs that are virtually absent from dorsum of head, vertex, mesosoma and petiole, except for a few scattered hairs at base of pronotal teeth. Sides and apex of gaster with numerous semi-erect to erect, medium length hairs and with somewhat dilute, silvery, appressed pubescence lining posterior margin of first gastral segment. Antennae and legs with yellow, appressed pubescence and numerous relatively short erect hairs.

Black, with mandibular masticatory border and antennal scapes reddish brown. Funiculus a shade lighter with extreme tip of last segment narrowly black. Legs mostly yellow, except distal portion of femora, proximal ends of tibiae and first tarsal segment, that are medium to dark reddish brown.

Type Material

Kohout (2007) - Holotype worker. Type locality: INDONESIA, Misool I., Waigamma (O. Beccari), Museo Civico di Storia Naturale, Genoa (examined).

References