Polyrhachis crawleyi

Polyrhachis crawleyi is uncommon with a rather patchy distribution across northern Australia. It is apparently restricted to open eucalypt forests and savannah woodlands, preferring patches of bare ground without a covering of grass to excavate their ground-based nests.

Identification
A member of the penelope species-group in the Polyrhachis subgenus Hagiomyrma. Kohout (1988): Similar to Polyrhachis ammonoeides. P. crawleyi is smaller (HL < 1.80), has longer antennal scapes (SI > 155) and the body is covered by very fine, somewhat dilute silvery pubescence. P. ammonoeides is always larger (HL > 1.90), with much shorter antennal scapes (SI < 148), a generally more glossy appearance, and with pubescence virtually absent from all body surfaces except the gaster. The widely divergent propodeal spines are almost straight in P. crawleyi, while in P. ammonoeides their tips are distinctly turned outwards.

Kohout (2013): Polyrhachis crawleyi is rather similar to Polyrhachis cracenta, but is separable by its consistently smaller size and closely reticulate-punctate sculpturation of the body, with distinguishing characters provided in the remarks of the latter species.

Distribution
Found in North Queensland and the Northern Territory. It is known from Lakefield on Cape York Peninsula south to Rockhampton, areas to the south of the Gulf of Carpentaria, and the Darwin district (Kohout 1988).

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Castes
Male and immature stages were reported in F.P. Dodd’s collection, however, their location is unknown and the material is probably lost.

Nomenclature

 *  crawleyi. Polyrhachis (Hagiomyrma) ammonoeides var. crawleyi Forel, 1916: 447 (w.) AUSTRALIA. Raised to species: Kohout, 1988c: 433.

Worker
(syntypes cited first): TL c. 6.20-6.60, 6.65-8.01; HL 1.53 1.69, 1.53-1.90; HW 1.25-1.31, 1.25-1.47; CI 77 82, 76-82; SL 1.93 2.12, 1.93-2.34; SI 154 162, 154-170; PW 0.87-0.91, 0.87-1.06; MW 0.59, 0.59- 0.69; PMI 147, 147-164; MTL 2.25 2.47, 2.25-2.75; (3+25 measured).

Anterior clypeal margin medially with shallow, truncate, denticulate flange, flanked by blunt teeth. Clypeus with distinctly raised median carina; sinuate in profile with moderately impressed basal margin. Frontal triangle poorly indicated. Frontal carinae sinuate with moderately raised margins; central area relatively wide with rather flat frontal furrow. Sides of head in front of eyes converging towards mandibular bases in almost straight line; behind eyes, sides rounding into convex occipital margin. Eyes convex, in full face view clearly breaking lateral cephalic outline. Ocelli lacking. Pronotal humeri dilated, distinctly rounded with weakly raised margins; dorsum with lateral margins distinctly emarginate or notched at about midlength, subparallel or weakly diverging towards promesonotal suture. Lateral margins of mesonotum converging posteriorly and weakly raised towards laterally impressed, medially flat metanotal groove. Propodeal dorsum with margins terminating in broad-based, long, slender, widely divergent, acute spines. Anterior face of petiole in side view rounding dorsally into long, slender, widely divergent spines, dorsum between spines deeply concave. Base of first gastral segment widely rounding onto dorsum.

Mandibles longitudinally striate with numerous piliferous pits. Head and mesosoma closely reticulate-punctate; spines sculptured for most of length, tips smooth. Gaster finely shagreened.

Mandibles with numerous medium length, golden hairs at masticatory borders; distinctly shorter and closely appressed hairs towards mandibular bases. Only a few anteriorly directed setae fringing anterior clypeal margin. Several paired, medium length hairs on clypeus, along frontal carinae and vertex. Somewhat longer, variously inclined hairs on dorsum of mesosoma and fore coxae; distinctly shorter hairs on venter of mid and hind coxae and femora. Gaster with numerous, posteriorly directed golden hairs, rather short on dorsum, distinctly longer and more abundant on venter and around apex. Closely appressed, somewhat medially radiating golden pubescence with somewhat brassy hue, over most dorsal body surfaces, including dorsum of gaster, where it is rather abundant, completely hiding underlying sculpturation; pubescence more sporadic and mostly silvery on sides of head, mesosoma and venter of gaster.

Black; mandibular teeth and appendages usually very dark reddish-brown.

Queen
TL c. 9.83; HL 2.03; HW 1.57; CI 77; SL 2.15; SI 137; PW 1.81; MTL 2.82 (1 measured).

Apart from sexual characters very similar to worker, except: pronotal dorsum with humeri subacute, margins widely rounded behind. Mesoscutum marginally wider than long; median line distinct, bifurcate anteriorly; parapsides flat anteriorly, weakly raised posteriorly; anterior margin of mesoscutum evenly rounded; dorsum relatively low and very weakly convex in lateral view; mesoscutellum only weakly elevated above dorsal plane of mesoscutum. Propodeal and petiolar spines similar to those in worker, but distinctly shorter. Sculpturation, pilosity, pubescence and colour virtually identical to worker.

References based on Global Ant Biodiversity Informatics

 * Andersen A. N., B. D. Hoffmann, and S. Oberprieler. 2016. Diversity and biogeography of a species-rich ant fauna of the Australian seasonal tropics. Insect Science DOI 10.1111/1744-7917.12402
 * Heterick B. E., B. Durrant, and N. R. Gunawardene. 2010. The ant fauna of the Pilbara Bioregion, Western Australia. Records of the Western Australian Museum, Supplement 78: 157-167.
 * Kohout R. J. 1988. Nomenclatural changes and new Australian records in the ant genus Polyrhachis Fr. Smith (Hymenoptera: Formicidae: Formicinae). Memoirs of the Queensland Museum 25: 429-438
 * Kohout R.J. 2013. Revision of Polyrhachis (Hagiomyrma) Wheeler, 1911 (Insecta: Hymenoptera: Formicidae: Formicinae). Memoirs of the Queensland Museum  Nature 56: 487577