Prionopelta robynmae

This species is exceptionally widespread for a member of this genus, occurring from PNG in the north to Victoria and Western Australia in the south. It also shows considerable ecological variability with specimens being found in a range of forested habitats including rainforests, open forests, paperbark swamps and Picabean palm forests. Foraging workers occur in leaf litter while nests have been found in soil under objects, between rock slices and in rotten wood.

Identification
Anterolateral corners of head, near mandibular insertions, rounded. Pronotal sculpturing consisting of small, closely spaced foveae which contrast markedly with the widely spaced foveae on mesonotum and propodeum, the foveae on the propodeum varying strongly in density across its width (weakest medially, stronger laterally). Body small, head width less than 0.48mm but petiole relatively broad, PetW greater than 0.22mm.

P. robynmae is most similar to P. kraepelini but differs in having small foveae on the pronotum rather than small punctures, stronger variation in the density of sculpturing across the width of the propodeum, in having a broader petiolar node (width greater than 0.22mm versus less than 0.21mm in P. kraepelini) and in having a relatively longer and narrower head (although the smallest P. robynmae workers are essentially identical to similarly sized P. kraepelini workers).

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

Nomenclature

 *  robynmae. Prionopelta robynmae Shattuck, 2008b: 30, figs. 6, 7, 17-19, 23 (w.) AUSTRALIA.

Holotype worker from 1.5km EbyN Mt. Sorrow, 16°05’S 145°27’E, Queensland, A. Calder & T. Weir, 25 March 1984, litter sample, rainforest on stony slope (, ANIC 32-039009). Eight paratype workers, same data as holotype (,, , ANIC 32-031327).

The following notes are from Shattuck (2008):

Specimens here placed in P. robynmae were previously considered to belong to P. kraepelini and/or P. opaca. However, the above diagnosis will separate these specimens from others in the genus and suggest that they belong to a distinct species. This species shows only slight and minimal variation in overall colour (from light to dark yellow-brown) and sculpturing (in the density of punctations on the head and dorsal mesosoma). Additionally, no geographic pattern is apparent in this variation and it seems to be randomly distributed geographically. However, the species does show considerable variation in body size. For example, numerous workers from Mt. Bartle Frere, Queensland, are consistently larger than any other known specimens while specimens from Mt. Webb Nat. Pk, Queensland, are distinctly smaller. But while these specimens differ in size they are essentially identical in all other characters to more typical specimens placed in this taxon with no indication that they represent a separate species.

Description
Anterolateral corners of head, near mandibular insertions, rounded and lacking a tooth. Dorsal pronotal sculpturing consisting of small closely spaced foveae which contrast markedly with the widely spaced foveae on the mesonotum and propodeum. Foveae on dorsum of propodeum varying across its width (weakest medially, stronger laterally). Lateral mesosomal sculpturing consisting of small, widely spaced foveae on pronotum and anterior region of mesopleuron, ventral regions of mesopleuron and propodeum weakly striate, posterodorsal region of mesopleuron and majority of propodeum smooth. Fenestra present within subpetiolar process. Colour pale yellow to yellow-red, queens generally slightly darker.

Measurements. (n=19) CI 72–78; HL 0.46–0.63; HW 0.35–0.47; ML 0.56–0.73; PetL 0.15–0.19; PetW 0.22–0.28; PI 131–165; SI 64–73; SL 0.24–0.34; T1W 0.32–0.41.