Polyrhachis aculeata species-group

The Polyrhachis aculeata species-group is comprised of species in the subgenus Myrma. It has been most recently been reviewed by: Kohout, R.J. 2013. A review of the Polyrhachis aculeata species-group of the subgenus Myrma Billberg (Hymenoptera: Formicidae: Formicinae), with keys and descriptions of new species. Australian Entomologist, 40, 137-171.

Worker
Relatively small ants (HL <1.90) with characteristics of the genus and subgenus. Head with closely approximated frontal carinae. Most species with peculiar, posteriorly truncate eyes, closely resembling those in species of the subgenus Hemioptica Roger; however, eye shape varying within group from posteriorly truncate (as in Polyrhachis aculeata), to relatively flat and conspicuously posteriorly protracted (as in Polyrhachis pubescens or Polyrhachis palawanensis), or only mildly truncate (as in Polyrhachis latona or Polyrhachis numeria), or virtually normal (as in Polyrhachis murina). Dorsum of mesosoma laterally marginate, evenly convex in side view, with only weakly indicated border between propodeal dorsum and declivity (as in Polyrhachis aculeata), or with a distinct transverse carina dividing propodeal dorsum from shallowly concave declivity (as in P. palawanensis). Pronotal shoulders armed with relatively strong, acute, anterolaterally directed spines that are relatively long (as in P. aculeata) or short (as in P. murina); propodeum armed with upturned, acute, minute teeth or tubercles. Petiolar node armed with two moderately long (as in P. aculeata or P. selecta Forel) or relatively short spines (as in Polyrhachis noonananti); spines situated at dorsolateral angles of petiole and separated by transversely broad, more-or-less convex, dorsal margin, which is mostly entire but may be furnished with an intercalary tooth (as in P. aculeata and Polyrhachis dimoculata), or weakly medially notched (as in Polyrhachis cybele). Lateral margin of petiole below base of spine with a relatively short tooth (as in P. cybele or P. pubescens), or a somewhat lengthened and flattened tooth (as in P. murina or Polyrhachis starri), which is entire or dorsally notched.

Queen
Apart from larger size and usual sexual characters, including three ocelli and fully developed mesosoma with wings, very similar to worker.

Male
The male is known for only three species: P. aculeata (see Forel, 1893: 28), P. selecta (Forel, 1911: 215-216) and P. pubescens (Fuminori Ito, private collection and QMBA). Their diagnosis is beyond the purpose and scope of this paper.

Within the group the species tend to polarise into two complexes, centering on either P. aculeata or P. pubescens. The Polyrhachis aculeata-complex includes jet-black species with the whole body smooth and highly polished (except in P. dimoculata). Pilosity in this group consists of medium length, erect or semierect hairs, variously distributed over most body surfaces, that range from rather sporadic (as in Polyrhachis hemiopticoides) to relatively abundant (as in Polyrhachis gibbosa). Closely appressed pubescence is virtually lacking in most species, except in P. gibbosa, where it is present mostly along the lateral margins of the mesosomal dorsum and sides. The aculeate complex is known from Sri Lanka, India and Thailand eastwards to the Philippines, Borneo and Indonesia, including Sumatra, Java and Sulawesi. The pubescens-complex includes species with dorsal body surfaces more-or-less distinctly reticulate-punctate or longitudinally striate, with the sculpture of most species partly or completely obscured by closely appressed, rather abundant, silvery-grey or golden pubescence. Species in this complex have rather short, erect hairs distributed in various densities over most body surfaces. The pubescens-complex is known from India, Thailand, Vietnam, China, Taiwan and Japan and southwards to the Philippines, Peninsular Malaysia, Borneo, Sumatra, Java and Sulawesi.