Polyergus samurai

Polyergus samurai is dulotic with Formica japonica as its main slave along with Formica hayashi occasionally. A colony with both Formica fukaii and F. japonica as slaves has been observed on Mt. Zao, Miyagi Prefecture (Sonobe, unpublished); this seems to be a rare occurrence. P. samurai nests in the soil and is seldom seen on the ground except when slave-raiding. Raids are carried out at around 3 to 4 pm during summer, when cocoons of slave species are to be found. Hasegawa & Yamaguchi (1995) reported the detailed ecology and raiding behavior of this species. Less common in Shikoku and Kyushu than elsewhere. Nuptial flights occur around July. Chromosome number n = 27 (Crozier, 1970) (Japanese Ant Image Database). Within its range it is the lone Polyergus species. Polyergus samurai is better known from studies of Japanese populations and is relatively poorly studied where it occurs in mainland Asia.

Identification
There was only minor variation among individuals detected among the specimens studied. Wheeler (1927) noted that the Chinese population he described as the subspecies mandarin was possibly blacker than the Japanese population. However, a small sample of workers from Beijing I obtained during this study had coloring indistinguishable from Japanese samples, and photographs sent to me of worker and male specimens from Hebei look typical, including the starkly white appendages of the male.

Polyergus samurai is probably not sympatric with any other species. It is easily distinguished from most other Polyergus species by its dark brown color, appearing nearly black in the field. It is closest to Polyergus nigerrimus, a smaller, darker, shinier species that lives in arid regions to the west of the range of samurai. Polyergus samurai males are notable for their striking white wings (even the veins are very pale yellow), and whitish appendages, including the mouthparts. Gynes also have white wings, with pale brown veins, and partially light brown appendages. This is in contrast to the dark brown appendages, brownish veins and infuscation of the wings of both sexes of nigerrimus.

Distribution
This species occurs in humid temperate Asia: Japan, Korea, China and southeastern Russia (teste Kupyanskaya 1990).

Distribution based on Regional Taxon Lists
Palaearctic Region: China, Democratic Peoples Republic of Korea, Japan , Republic of Korea, Russian Federation.

Biology
The hosts of samurai in Japan are Formica japonica and rarely, Formica hayashi and even Formica fukaii (of the F. exsecta group), while the types of “subspecies mandarin” were collected with the F. rufibarbis-group species Formica glabridorsis. Polyergus samurai is relatively well studied by several Japanese myrmecologists, but is only poorly known in its mainland Asian range. Terayama, et al. (1993) described four ergatoids found in two colonies of samurai, reporting they had “a well developed spermatheca”, and surmised that they can produce female offspring (though they did not confirm insemination). Hasegawa and Yamaguchi (1994, 1995) reported for this species (and typically for the genus) that raids mostly occurred on warm, sunny days, and mating flights only occurred on sunny days. According to these authors, time of initiation of raids and walking speed of raiders are related to simple environmental variables, especially temperature. Tsuneoka (2008) reported that colonies had a single gyne, housed colony populations of the host Formica japonica much larger than normal host colonies, and that the larger colony size in the parasite colony resulted in typical nest structure, but larger nest dimensions than those of unparasitized F. japonica.

List of Known Hosts
This species is known to enslave the following species:
 * (rare)
 * (uncommon)
 * (common host)
 * (common host)

Castes
Terayama et al. (1993) described dimorphic queens: winged and ergatoid

Nomenclature

 *  samurai. Polyergus rufescens subsp. samurai Yano, 1911: 110, fig. 1 (w.q.) JAPAN. Terayama, Yamaguchi & Hasegawa, 1993: 511 (ergatoid q.); Imai, 1966: 119 (k.). Raised to species: Emery, 1925b: 269; Wheeler, W.M. 1927e: 3. Senior synonym of mandarin: Trager, 2013: 522. See also: Kupyanskaya, 1990: 209.
 * mandarin. Polyergus samurai subsp. mandarin Wheeler, W.M. 1927e: 4 (w.) CHINA. Junior synonym of samurai: Trager, 2013: 522.

Worker
Trager (2013) - (N=24) HL 1.40–1.76 (1.56), HW 1.29–1.64 (1.47), SL 1.12–1.32 (1.22), ½ VeM 2–5 (2.92), ½ PnM 3–8 (5.67), WL 2.12–2.62 (2.41), GL 1.84–2.40 (2.15), HFL 1.68–2.04 (1.85), CI 92–97 (94), SI 76–93 (83), HFI 121–140 (126), FSI 143–159 (1.53), LI 3.52–4.38 (3.97), TL 5.40–6.72 (6.13).

Head narrowly hexagonal (truncate-ovate), length greater than breadth; with moderate vertex pilosity; scapes about reaching vertex corners, gradually thickening apically in distal half; pronotum with 5–16 erect macrosetae; mesonotum with profile flat for most of its length, with short posterior declivity; propodeal profile subquadrate, with concave posterior declivity; petiole more or less straight-sided above spiracles or convergent dorsad, petiolar dorsum flat or convex, shallowly or not at all emarginate; first tergite densely pubescent; tergite pilosity relatively scant compared to other Polyergus, concentrated in anterior-lateral portions, weakly flexuous, relatively widely separated.

Head matte; mesonotum matte; gaster matte, sometimes weakly shining on the sides.

Color uniform dusky reddish brown or with a slightly darker gaster; with dusky yellow-brown appendages; pilosity yellowish brown.

Etymology
Trager (2013) - This ant was named for the traditional Japanese warrior class, the “Samurai,” presumably by analogy to calling these ants “Amazons” in European languages.

References based on Global Ant Biodiversity Informatics

 * Abe T. 1971. On the food sharing among four species of ants in a sandy grassland. I. Food and foraging behaviour. Japanese Journal of Ecology 20(6): 219-230.
 * Chen Z. L., S. Y. Zhou, D. D. Ye, Y. Chen, and C. W. Lu. 2013. Moleular phylogeny of the ant subfamily Formicinae (Hymenoptera, Formicidae) from China based on Mitochondrial genes. Sociobiology 60(2): 135-144.
 * Choi B.M. 1986. Studies on the distribution of ants (Formicidae) in Korea. Journal of Chongju National Teacher College 23: 317-386.
 * Choi B.M., K. Ogata, and M. Terayama. 1993. Comparative studies of ant faunas of Korea and Japan. 1. Faunal comparison  among islands of Southern Korean and northern Kyushu, Japan. Bull. Biogeogr. Soc. Japan 48(1): 37-49.
 * Guénard B., and R. R. Dunn. 2012. A checklist of the ants of China. Zootaxa 3558: 1-77.
 * Hosoichi S., M. Yoshimura, Y. Kuboki, and K. Ogata. 2007. Ants from Yakushima Island, Kagoshima Prefecture. Ari 30: 47-54.
 * Hosoishi S., M. Yoshimura, Y. Kuboki, and K. Ogata. 2007. Ants from Yakushima Island, Kagoshima Prefecture. Ari 30: 47-54.
 * Hua Li-zhong. 2006. List of Chinese insects Vol. IV. Pages 262-273. Sun Yat-sen university Press, Guangzhou. 539 pages.
 * Kim B.J. 1996. Synonymic list and distribution of Formicidae (Hymenoptera) in Korea. Entomological Research Bulletin Supplement 169-196.
 * Kim B.J., S.J. Park, and J.H. Kim. 1996. Ants from Naejangsan national park (Hymenoptera: Formicidae). Korean J. Soil. Zoology &(2): 120-133.
 * Morisita M. 1945. Ants of the southern part of Hokkaido, Japan. [In Japanese.] Mushi 16:21-28.
 * Muñoz-López M., T. Palomeque, J. A. Carrillo, J. Pons, A. Tinaut, and P. Lorite. 2012. A new taxonomic status for Iberoformica (Hymenoptera, Formicidae) based on the use of molecular markers. Journal of Zoological Systematics and Evolutionary Research 50: 30-37.
 * Nanbu, T. 2004. Observations on Polyergus samurai's hunting method. (translated from Japanese) Reports of the Saitama Prefecture Animal Research Association. 48:61
 * Paik W.H. 1984. A checklist of Formicidae (Hymenoptera) of Korea. Korean J. Plant Prot. 23(3): 193-195.
 * Radchenko, A. 2005. Monographic revision of the ants (Hymenoptera, Formicidae) of North Korea. Annales Zoologici 55(2): 127-221.
 * Sakai H. 2002. Reproductive flight season of Japanese ants. Ari 26: 33-39.
 * Sanllorente O., P. Lorite, F. Ruano, T. Palomeque, and A. Tinaut. 2017. Phylogenetic relationships between the slave-making ants Rossomyrmex and their Proformica hosts in relation to other genera of the ant tribe Formicini (Hymenoptera: Formicidae). J Zool Syst Evol Res. 1–13.
 * Sato T., N. Tsurusaki, K. Hamaguchi, and K. Kinomura. 2010. Ant fauna of Tottori prefecture, Honshu, Japan. Bulletin of the Tottori Prefectural Museum 47: 27-44.
 * Terayama M. 1977. Checklist of the known ants of Saitama Prefecture. Insects and nature 12(4): 26-27
 * Terayama M. 1992. Structure of ant communities in East Asia. A. Regional differences and species richness. Bulletin of the Bio-geographical Society of Japan 47: 1-31.
 * Terayama M., K. Ogata, and B.M. Choi. 1994. Distribution records of ants in 47 prefectures of Japan. Ari (report of the Myrmecologists Society of Japan) 18: 5-17.
 * Terayama M., S. Kubota, and K. Eguchi. 2014. Encyclopedia of Japanese ants. Asakura Shoten: Tokyo, 278 pp.
 * Terayama M., T. Yamaguchi, and E. Hasegawa. 1993. Ergatoid queens of slave-making ant Polyergus samurai Yano (Hymenoptera, Formicidae). Jpn. J. Entomol. 61: 511-514.
 * Terayama M., and S. Kubota. 2002. Ants of Tokyo, Japan. ARI 26: 1-32.
 * Trager J. C. 2013. Global revision of the dulotic ant genus Polyergus (Hymenoptera: Formicidae, Formicinae, Formicini). Zootaxa 3722(4): 501-548.
 * Tsuneoka Y. 2009. Colony collection of Polyergus samurai and Formica japonica in winter. Ari 32: 67-74.
 * Yamaguchi. T. and E. Hasegawa. 1994. Slave making raids of the ant Polyergus samurai. Abstracts of papers presented at 35th Annual Meeting of the Myrmecological Society of Japan held on August 27th to 29th, 1992, a the Bandai Lodge of Toho University, Fukushima Prefecture. ARI Reports of the Myrmecologists Society (Japan) 18: 37
 * Yamane S., Y. Harada, and K. Eguchi. 2013. Classification and ecology of ants. Natural history of ants in Southern Kyushu. 200 pages
 * Yano M. 1911. A new slave-making ant from Japan. Psyche (Camb.) 18: 110-112.