Polyrhachis geometrica

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Polyrhachis geometrica
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Camponotini
Genus: Polyrhachis
Subgenus: Aulacomyrma
Species: P. geometrica
Binomial name
Polyrhachis geometrica
Smith, F., 1859

Polyrhachis geometrica casent0901807 p 1 high.jpg

Polyrhachis geometrica casent0901807 d 1 high.jpg

Specimen Labels

Nothing is known about the biology of Polyrhachis geometrica.

Identification

Kohout (2007) - P. geometrica is similar to the other species of the complex, notably to Polyrhachis annulata, Polyrhachis breviata and Polyrhachis monticola, and in addition to the characteristic “geometrical” sculpture they share the medially emarginate dorsal margin of the petiole and rather shallowly concave base of the first gastral segment. However, geometrica is easily recognizable by the color of the front femora which are very light, yellowish brown in contrast to the entirely black femora of the middle and hind legs. In the other allied species the femora of all legs are more-or-less uniform in color.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

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

Check distribution from AntMaps.

Distribution based on specimens

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

Nomenclature

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

  • geometrica. Polyrhachis geometricus Smith, F. 1859a: 141 (w.) INDONESIA (Aru I.). Combination in P. (Aulacomyrma): Donisthorpe, 1932c: 453. See also: Kohout, 2007a: 222.

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) - TL c. 4.89-5.14 (4.89); HL 1.25-1.34 (1.25); HW 1.09-1.18 (1.09); CI 87-88 (87); SL 1.31-1.37 (1.31); SI 116-122 (120); PW 0.90-0.94 (0.94); MTL 1.25- 1.28 (1.25) (3 measured).

Anterior clypeal margin arcuate, only very shallowly truncate medially; clypeus virtually straight in profile. Frontal carinae strongly sinuate, with raised margins; central area relatively wide with distinct, longitudinal carina running towards anterior clypeal margin. Frontal triangle front of eyes only weakly converging anteriorly. Pronotum immarginate, widest just below humeri that are armed with small, acute, dorso-ventrally flattened, triangular teeth. Promesonotal suture distinct; metanotal grove lacking, position indicated by slight change in direction of dorsal sculpture and slight depression in lateral outline. Propodeum unarmed. Petiole with dorsal margin emarginate between distinct intercalary teeth; lateral spines relatively long, curved backwards. Anterior face of first gastral segment very shallowly concave medially at base.

Head in front of eyes and on sides more-or-less regularly, longitudinally striate; preoccipital margin with median striae transversely bowed and lateral striae converging anteriorly towards central area between frontal carinae. Sculpture of pronotal dorsum consisting of inverse, wide U- and V-shaped striae, that are laterally uninterrupted and continuous along sides. Mesonotal dorsum with more regular, semicircular striae, outermost forming an ill-defined lateral margin; propodeal dorsum with striae continued obliquely along sides. First gastral segment distinctly, and more densely, longitudinally striate; striae converging anteriorly towards base.

Holotype with pilosity almost completely absent from dorsum of mesosoma and gaster, a few erect to semierect, short hairs on dorsum and sides of head, vertex, along antennal scapes and on tibia of middle and hind legs. Rather sparse, Appressed, silvery pubescence scattered over dorsum of head and mesosoma; more abundant along dorso-posterior borders of gastral segments.

Black, including antennal scapes, coxae, trochanters (except narrow light band at distal ends) and femora of middle and hind legs. Femora of front legs, tibiae and tarsi distinctly light yellowish or reddish brown, except proximal and distal ends of segments very dark brown or black. Basal funicular segments very dark brown with paler, reddish brown bands at their apices; lighter bands becoming progressively wider in distal funicular segments, that are mostly pale, reddish-brown.

Type Material

Kohout (2007) - Holotype worker. Type locality: INDONESIA, Aru I. (A. R. Wallace), Oxford University Museum of Natural History (examined).

The following notes on F. Smith type specimens have been provided by Barry Bolton (details):

Polyrhachis geometricus

Holotype worker in Oxford University Museum of Natural History. Labelled “Aroo” (= Aru I., New Guinea) and with a Donisthorpe type-label.

References