Polyrhachis mucronata

Colonies of P. mucronata build nests the leaves of rainforest trees and shrubs, using mostly larval silk combined with leaf fragments and other vegetation debris (see image below).

Identification
Kohout (2010) - Among the Australian species of Myrmhopla, Polyrhachis mucronata is very distinct, however, it superficially resembles some species of the subgenus Cyrtomyrma. Despite their general similarity and identical nesting habits, P. mucronata can be easily distinguished from Cyrtomyrma species by the form of its petiole. The petiolar node in P. mucronata is columnar and armed with two, more-or-less horizontal, posteriorly directed spines that conform to the shape of the anterior gaster. The petiole also bears a pair of short, intercalary teeth. In contrast, in Cyrtomyrma species, the petiole is scale-like and armed with four teeth or spines of various configurations. Additionally, all Australian Cyrtomyrma species have a distinct posterolateral carina separating the gena from the ventral parts of the head. This carina is lacking in P. mucronata-group species. The two groups also differ in their immature stages with the pupae of Myrmhopla species being enclosed in cocoons, while in Cyrtomyrma species the pupae are naked (Kohout, 2006b).

Distribution
Polyrhachis mucronata ranges from the islands of eastern Indonesia and New Guinea south to northern Queensland where it reaches the southern limit of its distribution. It is a relatively common species in the monsoon rainforests of Cape York Peninsula and the lowland rainforests of the Wet Tropics.

Distribution based on Regional Taxon Lists
Australasian Region: Australia. Indo-Australian Region: Indonesia, New Guinea, Philippines.

Castes
Males and immature stages (eggs, larvae and pupae) deposited in QM spirit collection.

Nomenclature

 *  mucronata. Polyrhachis mucronatus Smith, F. 1859a: 140 (w.) INDONESIA (Aru I.). Combination in P. (Myrmhopla): Emery, 1925b: 196. Senior synonym of cyrtomyrmoides: Kohout, 2010: 182. Current subspecies: nominal plus janthinogaster, japensis.
 * cyrtomyrmoides. Polyrhachis (Myrmhopla) cyrtomyrmoides Donisthorpe, 1947d: 195 (w.q.) NEW GUINEA. Junior synonym of mucronata: Kohout, 2010: 1832.

Kohout (2010) - When describing Polyrhachis cyrtomyrmoides, Donisthorpe (1947: 195) emphasised its close resemblance to ants of the subgenus Cyrtomyrma but failed to note its remarkable similarity to P. mucronata. I had the opportunity to examine the syntypes of P. cyrtomyrmoides, supplemented by additional specimens in the CASC collection (Maffin Bay, 17.vi.1944, E.S. Ross). Their comparison with the holotype of P. mucronata (OXUM) and abundant material of that species from New Guinea and Australia (ANIC, BMNH, BPBM, MCZC and QM) revealed that the two species were very similar. As noted earlier by Kohout (2000: 206), the Australian and New Guinean populations of P. mucronata differ somewhat from the holotype, with some specimens from Australia being remarkably close to those of P. cyrtomyrmoides, sharing the rather highly polished appearance which is typical of the latter species. However, the density of the generally fine reticulate-punctate sculpturation varies not only between different populations, but also to some extent between specimens of a single colony. The colour of the legs also varies, generally being a lighter red in Australian specimens and a darker, reddish-brown in most of New Guinean specimens. In addition, the eyes vary in the degree of their convexity with specimens from the Wet Tropics having the eyes simply convex, similar to those in P. cyrtomyrmoides, while the eyes in specimens from the mid and northern Cape York Peninsula are virtually protuberant. When considered individually, specimens of some populations appear quite distinct, however, when all the available material from the whole distribution range is compared, no consistent differences between P. cyrtomyrmoides and P. mucronata are evident. I therefore believe that the separate specific status of the former is not justified and consider them conspecific.

Worker
Kohout (2010) - (holotype cited first) TL c. 5.55, 5.34-6.50; HL 1.43, 1.40-1.65; HW 1.17, 1.12-1.31; CI 82, 76-82; SL 1.84, 1.65-2.12; SI 157, 146-164; PW 1.00, 0.94-1.15; MTL 1.93, 1.81-2.31 (31 measured).

Anterior clypeal margin medially with shallow flange, flanked laterally by acute angles. Clypeus with poorly defined median carina; clypeus in profile straight anteriorly, posteriorly rounding into moderately impressed basal margin. Frontal carinae sinuate with moderately raised margins. Sides of head in front of eyes weakly convex converging towards mandibular bases; behind eyes sides rounding into convex occipital margin. Eyes relatively large and convex, in full face view clearly exceeding lateral cephalic outline. Ocelli lacking. Mesosoma immarginate. Pronotal humeri armed with short, acute teeth. Promesonotal suture distinct; mesonotum virtually flat in profile. Mesopleural process a blunt lobe; metanotal groove indicated as a thin, bowed line. Propodeal dorsum very short, armed with rather strong, obliquely directed, diverging, acute spines; inner borders of spines continued medially for a short distance, but failing to meet, propodeal dorsum descending into relatively high, oblique declivity in uninterrupted line. Petiole columnar, dorsum armed with two strong lateral spines that conform to shape of anterior gaster and two short, acute intercalary teeth medially. Anterior face of first gastral tergite straight, widely rounding onto dorsum of segment.

Mandibles very finely, longitudinally striate with numerous piliferous pits. Head and dorsum of mesosoma and petiole finely reticulate-punctate with sculpturation distinctly coarser on sides of mesosoma; meso- and metapleurae weakly rugose and somewhat wrinkled. Gaster finely shagreened.

Mandibles at masticatory and outer borders with a few, curved, golden hairs. Anterior clypeal margin with several anteriorly directed setae medially and a pair of longer, suberect hairs arising from just behind margin. Tuft of medium length, erect hairs in front of subpetiolar process. Apical segments on dorsum and venter of gaster with a number of semierect, posteriorly directed, golden hairs. Very short, closely appressed pubescence arising from minute punctures and pits, distributed over most body surfaces, more distinct on gastral dorsum.

Body black, polished; mandibular bases, antennal scapes, fore coxae and tarsi black or very dark reddish-brown; mandibular masticatory borders, condylae, apical antennal segments and most of legs, except tarsi, light to medium reddish-brown.

Queen
Kohout (2010) - TL c. 6.95-7.81; HL 1.65-1.75; HW 1.25-1.34; CI 75-77; SL 1.96-2.12; SI 153-160; PW 1.56-1.68; MTL 2.18-2.37 (10 measured).

Very similar to worker with usual differences indicating caste, including three ocelli, complete thoracic structure and wings. Median clypeal carina somewhat more distinct. Pronotal teeth dorsoventrally flattened; mesoscutum in lateral view with anterior margin widely rounding onto flat dorsum; median line bifurcate anteriorly; parapsides rather flat, weakly raised posteriorly; mesoscutellum convex, elevated above dorsal plane of mesosoma; metanotal groove strongly impressed. Propodeal spines shorter than in worker, almost straight; petiolar spines similar to those in worker but shorter. Sculpturation, pilosity, pubescence and colour virtually identical to worker.

Type Material
Kohout (2010) - Holotype worker: INDONESIA: Aru Is. (A. R. Wallace), (examined).



Polyrhachis mucronatus

Holotype worker in. Labelled “Aroo” (= Aru I., New Guinea) and with a Donisthorpe type-label.