Is Polyergus nigerrimus a synonym of P. samurai?
by James Trager

     In 1963, Marikovsky described the slender, blackish Amazon ant Polyergus nigerrimus from a colony encountered along the banks of the Jenisei River at Kyzyl in Siberian Russia. He provided notes on its morphology and biology and raids on its host, Formica gagates Latreille. The description (English version) and illustrations of worker and sexuals of this taxon, led me to wonder if that it might be conspecific with the better known eastern Asian black species P. samurai Yano. Marikovsky, perhaps unaware of the existence of P. samurai, distinguished P. nigerrimus from the common Eurasian P. rufescens, but did not provide any information on possible differences between the two black forms.
      I thus initiated an effort to acquire for study specimens of this Siberian-Mongolian Amazon ant, a quest that has thus far remained fruitless. I have, at least, been able to acquire numerous specimens of P. samurai from Japan, as well as digital images of a type worker of this species housed at the Harvard Museum of Comparative Zoology.
Dr. Martin Pfeiffer also graciously provided digital images of a specimen of P. nigerrimus from his survey of ants of. Copies of the P. nigerrimus images from Mongolia by Dr. Pfeiffer are pasted in below.
(See http://antbase.de/mongolia/home.html for the originals now posted there).
      These materials deepen my suspicions about the synonymy of these two taxa, as I am unable to detect any significant differences in pilosity, sculture, head shape, propodeal or petiolar profile among the specimens and images studied. The type of P. samurai does appear somewhat more pubescent, but differences in type of lighting, lighting angle and focus could account for this. On the other hand, differences in host (F. gagates vs. F. japonica) and biogeography and habitat (Siberian semi-arid steppe versus humid temperate Japan, Korea and China) might indicate population-level difference of real taxonomic significance between these two taxa.
      So, the question posed in my title remains unanswered, but points to the difficulties posed by describing new species in isolation rather than in the proper context of a careful revison. It further points to the real need for such a revision of the genus Polyergus. There is good host-associate and morphological evidence, for example, that the real number of species in North America is not adequately represented by the available taxonomy. Whether this is also true in Eurasia is something I would like to figure out. Once again, then, I put forth a request for specimens, with particular interest in samples including host workers and sexuals from across Russia, Mongolia and China, areas that have become ever more accessible to modern collectors.

Marikovsky, P. I. 1963. [A new species of ant Polyergus nigerrimus Marik., sp. n. (Hymenoptera, Formicidae), and some traits of its biology.] Entomol. Obozr. 42: 110-114.

Full face view Polyergus nigerrimus

Even with my 30 years of looking at thousands of Polyergus specimens, full face, dorsal and lateral views of a worker of Polyergus nigerrimus from Mongolia are indistinguishable to me in any important way from similar views of Polyergus samurai.