Polyrhachis dahlii

As noted by Mann (1919), P. dahlii appears to be a relatively rare species, with its distribution centred on the Bismarck Archipelago. However, there are a few records of the species from New Britain (Gazelle Peninsula, Vunakanau, 11-20.v.1955; Kerevat, 2.ix.1955; Baining Mts, St Pauls, 4.ix.1955 – all J.L. Gressitt), and from the Solomons (San Christoval, Wainoni Bay; Three Sisters, Malapaina; Malaita, Auki; Florida, Tulagi – all W.M. Mann; Guadalcanal, Honiara, 13-16.xi.1953, J.D. Bradley). (Modified from Kohout, 2012.)

Identification
Kohout (1998) suggested Polyrhachis dahli unisculpta to be a junior synonym of Polyrhachis queenslandica and, consequently, a separate taxon from P. dahlii. To verify the identity of the three names, Kohout (2012) directly compared the syntypes of all taxa and confirmed that P. queenslandica and P. dahli unisculpta are undoubtedly conspecific and P. dahlii is a distinct species. The most obvious character separating P. dahlii from P. queenslandica is colour which, in the former, is yellow or very light yellowish brown with only the mandibular teeth, anterior clypeal margin, frontal carina and the lateral margins of pronotum and mesonotum narrowly bordered with brown. In contrast, P. queenslandica is virtually black or dark reddish-brown with the head a shade darker. The sculpturation of the head and mesosoma in P. dahlii is rather coarsely reticulate-punctate, while it is distinctly finer in P. queenslandica. The gaster in both species is very finely shagreened and highly polished. (Modified from Kohout, 2012.)

Distribution based on Regional Taxon Lists
Indo-Australian Region: Papua New Guinea, Solomon Islands.

Nomenclature

 *  dahlii. Polyrhachis dahlii Forel, 1901b: 30 (w.) NEW GUINEA (Bismarck Archipelago). Combination in P. (Myrmothrinax): Mann, 1919: 378. See also: Kohout, 2012: 35.

Syntype workers from Ralum, Bismarch Archipelago, 17.iii.97 (F. Dahl) (examined by Kohout, 2012).

Additional References

 * Kohout, R.J. 1998. New synonyms and nomenclatural changes in the ant genus Polyrhachis Fr. Smith (Hymenoptera:Formicidae: Formicinae). Memoirs of the Queensland Museum 42(2): 505-531.
 * Kohout, R.J. 2012. A review of the Australian Polyrhachis ants of the subgenera Myrma Billberg, Myrmatopa Forel, Myrmothrinax Forel and Polyrhachis Fr. Smith (Hymenoptera: Formicidae: Formicinae). Memoirs of the Queensland Museum – Nature 56(1): 25-59.