Polyrhachis anderseni

Polyrhachis anderseni is one of only a few lithocolous Polyrhachis species (the others are Polyrhachis thusnelda and Polyrhachis turneri) that build their nests inside rock crevices or on the sides of rock walls (Robson & Kohout 2005).

Identification
A member of the penelope species-group in the Polyrhachis subgenus Hagiomyrma. Polyrhachis andersoni is an easily recognisable species, featuring very closely approximated, upturned, petiolar spines. It somewhat resembles Polyrhachis archeri, however, in that species the anterior clypeal margin is produced into a median denticulate flange, while it is simply medially truncate in P. anderseni. The bases of the petiolar spines in P. archeri are more distant and the propodeal spines in lateral view are directed downwards, forming a continuous line with the arching profile of the mesosomal dorsum (Fig. 6C-D). In contrast, the bases of petiolar spines in P. anderseni are closer and the propodeal spines are more horizontal.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Castes
Known only from the worker caste.

Nomenclature

 *  anderseni. Polyrhachis (Hagiomyrma) anderseni Kohout, 2013: 528, figs. 6A-B (w.) AUSTRALIA.

Worker
(holotype cited first): TL c. 6.80, 5.90-6.80; HL 1.62, 1.43- 1.62; HW 1.43, 1.23-1.43; CI 88, 86-92; SL 2.09, 1.87-2.12; SI 146, 138-153; PW 1.28, 1.09-1.31; MW 0.76, 0.70-0.81; PMI 168, 149-168; MTL 2.25, 2.00-2.28 (14 measured).

Anterior clypeal margin truncate medially without distinct median flange; truncate portion denticulate, laterally delimited by acute teeth. Clypeus with distinct median carina; weakly convex in profile, posteriorly rounding into moderately impressed basal margin. Frontal triangle indistinct. Frontal carinae with weakly raised margins; central area relatively wide, flat. Sides of head in front of eyes converging towards mandibular bases in straight line; behind eyes, sides widely rounding into convex occipital margin. Eyes moderately convex, in full face view not or only marginally exceeding lateral cephalic outline. Ocelli lacking. Pronotal dorsum distinctly wider than long, widest at about midlength; humeri widely rounded, with shallow depression dorsally along narrowly raised, posteriorly converging lateral margins. Mesonotal dorsum with lateral margins shallowly emarginate towards poorly indicated metanotal groove. Propodeal margins terminating posteriorly in relatively short, horizontal and subparallel, acute spines; spines about half as long as distance between tips. Anterior face of petiole rounding dorsally into upturned, subparallel, or weakly divergent, acute spines; bases of spines closely approximated, petiolar dorsum between them deeply concave, forming open ‘U’ when viewed from behind. Posterior face of petiole distinctly swollen towards base. Anterior face of first gastral segment widely rounding onto dorsum.

Mandibles finely, longitudinally striate with numerous piliferous pits. Head, mesosoma and petiole finely and uniformly reticulate-punctate. Gaster shagreened.

Mandibular masticatory and outer borders with curved golden hairs and closely appressed shorter hairs towards bases. Anterior clypeal margin medially with several, medium length setae and a few short setae fringing margin laterally. Rather sporadic, relatively short, erect hairs on dorsum of head and body, hairs on gaster distinctly longer and more abundant. Silvery, appressed pubescence in various densities over most dorsal body surfaces; pubescence silvery or pale golden and more abundant on gastral dorsum, partly hiding underlying sculpturation.

Black, with mandibular teeth, condylae and apical funicular segments medium to dark reddish-brown. Legs, including coxae, dark to very dark reddish-brown.

Type Material


Type deposition: Holotype and 2 paratypes in ; most paratypes in, 2 paratypes each in , , , , and.

Etymology
Named in honor of Dr Alan N. Andersen of the CSIRO, TERC in Darwin, who has discovered many new species of Polyrhachis and other ants throughout the monsoonal and arid zones of the northern Australia.

References based on Global Ant Biodiversity Informatics

 * Andersen A. N., J. Lanoue, and I. Radford. 2010. The ant fauna of the remote Mitchell Falls area of tropical north-western Australia: Biogeography, environmental relationships and conservation significance. Journal of Insect Conservation 14: 647-661.
 * Kohout R.J. 2013. Revision of Polyrhachis (Hagiomyrma) Wheeler, 1911 (Insecta: Hymenoptera: Formicidae: Formicinae). Memoirs of the Queensland Museum  Nature 56: 487577