Polyrhachis lamellidens

Polyrhachis lamellidens is perhaps the best known and most studied of all members of the subgenus, probably due to its occurrence in a densely populated country with easy access to colonies (see Hung, 1970: 28–29) (Kohout, 2014). Its nesting habits are different from those of other species of the subgenus with their nests usually found in rotten logs (Yano, 1911) and tree stumps (J. Fellowes, pers. comm.), but also in the ground. Their parasitic lifestyle, in relation to Camponotus japonicus Mayr (as C. herculeanus japonicus) was observed under laboratory conditions by Kohriba (1963). (Kohout, 2014)

Identification
A member of the lamellidens group of the subgenus Polyrhachis. Like Polyrhachis craddocki, this is a very morphologically stable species with no significant variation between populations.

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

Polyrhachis lamellidens is known from Japan, Korea, Taiwan and China, including Hong Kong (Kohout, 2014).

Biology
Hung (1970) - Nests of lamellidens are usually found in rotten logs (Yano, 1911), but occasionally underground (Brown, pers. commun.). Yano (1911) also observed one colony to temporarily occupy a nest of Camponotus herculeanus japonicus in the ground while moving into a new nest in a bamboo fence. Kohriba (1963) put one female into the observation cage with 12 workers of Camponotus herculeanus japonicus after her nuptial flight. She was later accepted and her broods were tended by the host workers. The flight season is from late October to early November although male and female alates were also found in late July (Yano, 191 I). The chromosome numbers are n=21, 2n=42 (Imai, pers. commun.).

Ito et al. (2016) investigated the defensive function of petiole spines in queens and workers of this ant using the ant predating tree frog Hyla japonica. Ant workers have hook-like large spines on their petiole while the queen petiole has only small slightly curved spines. They found that intact workers of P. lamellidens are unpalatable while workers without spines and intact queens are palatable, indicating that the spines of workers provide an effective defense against the tree frogs.

Colony Founding
The following is a summery of observations made by Taku Shimada and reported on his blog site AntRoom between 2010 and 2015 (in Japanese, translated and summarised here). Observations were made both in the field as well as in laboratory colonies and involved numerous colonies collected over a number of years. Full details can be found at Colony Founding in Polyrhachis lamellidens.

The following steps seem essential for the successful establishment of a new nest by P. lamellidens queens:

1) The mated Polyrhachis lamellidens queen locates a nest of Camponotus japonicus.

2) A foraging C. japonicus worker is captured and subdued. The queen’s fore legs are used to transfer scent from the worker to her body.

3) The host nest is invaded and the C. japonicus queen is located.

4) The P. lamellidens queen attaches herself to the host queen's neck. They stay in close contact and transfer scent for up to 2 weeks. Host workers do not distinguish between the two queens and feed both.

5) The host queen is killed.

6) Workers feed the P. lamellidens queen over the winter period; her ovaries develop.

7) In spring, egg-laying begins with host workers tending the brood.

8) Over time, host workers die and are replaced with P. lamellidens workers. Eventually the colony becomes pure Polyrhachis lamellidens.

Feeding Biology
Polyrhachis lamellidens are omnivorous and will forage on a wide range of foods, including sap, aphid honeydew and dead insects and other arthropods. They are attracted to protein baits and when placed near the nest entrance large numbers of workers will recruit to the food source.

These ants have been observed feeding on a centipede. As they are not particularly strong hunters (for example, they lack a sting) it seems likely they were scavenging on a dead centipede rather than having captured a living one.

Other Ants
This species is a temporary parasite of (Kohriba, 1963),  (Sakai, 1990) and possibly  (Sakai, 1990).

Spider Mites
Polyrhachis lamellidens workers are attacked by spider mites that appear to specialise on ants. These mites show a strong preference to attach to the petiole as the majority of individuals have been observed in this position. The advantage of this placement is unclear, but it is likely the mites are either protected from removal by the ant or are attacking the soft tissue near the joint between the ant’s petiole and gaster.

Nomenclature

 *  lamellidens. Polyrhachis lamellidens Smith, F. 1874: 403 (w.) JAPAN. Donisthorpe, 1937a: 627 (q.); Koriba, 1963: 200 (l.); Wheeler, G.C. & Wheeler, J. 1970: 649 (l.); Hung, 1970: 29 (m.).

Worker
Hung (1970) - HW 1.70-2.08 mm, HL 1.88-2.25 mm, C1 84-94, SL 2.15-2.63 mm SI 122-134, PW 1. 10-1.50, mm, MPL 1.80-2.15 mm, MTL 2.65-3.08 mm, PSE1 140-233, PH 1.65-2.13 mm. Clypeus convex, with a sharp central longitudinal carina. No ocellus. Alitrunk margined with prominent ridges which are sharply interrupted at the pronounced promesonotal suture and the metanotal groove. Pronotum about as broad as long, its lateral ridge continued anteriorly on each side into a long spine, which is directed outward and forward and slightly curved downward at its tip. The spine is about as long as the pronotum. Mesonotum broader than long, bearing at the middle of each side a short rapidly tapering spine curved upward, outward and inclined backward. Propodeum about one-seventh longer than broad with ridge along the side extending posteriorly into a short, blunt spine which is about half the length of the propodeum. The ridge also continues down along the side of the declivity. Petiole columnar, anterior face convex, bearing a pair of 'long, somewhat flattened, hook-shaped spines, which diverge laterally and are inclined over the basal segment of the gaster. Gaster spherical with the tergite of the first segment covering almost half of the gaster. Mandibles, clypeus, occiput and legs with sparse, suberect hairs. Pubescence very sparse on the head and gaster, more abuudant on the pleurae and base of the gaster. Head very dusky red and finely shagreened. Alitrunk and petiole dark reddish-brown and punctate-rugulose. Gaster very dusky red and very shiny.

Kohout (2014) - (syntype cited first): TL c. 8.82, 7.31 – 9.07; HL 2.18 (head detached from the body), 1.78 – 2.18; HW 1.96, 1.56 – 1.96; CI 90, 88-90; SL 2.56, 2.09 – 2.65; SI 131, 130 – 136; PW 1.36, 1.03 – 1.36; PeH 1.76, 1.53 – 2.03; PeI 81, 81 – 94; MTL 3.02, 2.81 – 3.21 (1+18 measured).

Queen
Kohout (2014) - TL c. 10.08 – 10.63; HL 2.12 – 2.28; HW 1.75 – 1.87; CI 82 – 83; SL 2.31 – 2.40; SI 128 – 132; PW 2.03 – 2.18; PeH 1.18 – 1.31; PeI 53 – 62; MTL 2.87 – 3.12 (4 measured).

Male
Hung (1970) - Black and hairy with yellowish-brown hairs all over the body except the legs. Mandibles with pointed apex, masticatory border unarmed. Mesonotum convex, alitrunk without any spines. Petiolar spines short and tuberculate. Hind wing without discoidal cell. Genitalia with serrated lamina aedeagalis and pegged cuspis volsellaris and digitus volsellaris.

Larva
Immature stages described by Koriba (1963: 200) and Wheeler & Wheeler (1970: 649).

References based on Global Ant Biodiversity Informatics

 * Baba, K. 1935. Some hymenopterous insects from Sado Island. [In Japanese.]. Mushi 8:83-85.
 * 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. 1988. Studies on the distribution of ants (Formicidae) in Korea (5) Ant fauna in Is. Kanghwado. Chongju Sabom Taehak Nonmunjip (Journal of Chongju National Teacher' College) 25: 217-231.
 * 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.
 * Choi B.M., Kim, C.H., Bang, J.R. 1993. Studies on the distribution of ants (Formicidae) in Korea (13). A checklist of ants from each province (Do), with taxonomic notes. Cheongju Sabom Taehakkyo Nonmunjip (Journal of Cheongju National University of Education) 30: 331-380.
 * Donisthorpe H. 1937. Some new forms of Formicidae and a correction. Annals and Magazine of Natural History (10)19: 619-628.
 * Forel A. 1901. Formiciden des Naturhistorischen Museums zu Hamburg. Neue Calyptomyrmex-, Dacryon-, Podomyrma- und Echinopla-Arten. Mitt. Naturhist. Mus. Hambg. 18: 43-82.
 * Guénard B., and R. R. Dunn. 2012. A checklist of the ants of China. Zootaxa 3558: 1-77.
 * Ha S.J, S.J. Park, and B.J. Kim. 2002. Comparative ant faunas between Seonyudo and seven other islands of West Sea in Korea. Korean Journal of Entomology 32(2): 75-79.
 * Hosoishi S., M. Yoshimura, Y. Kuboki, and K. Ogata. 2007. Ants from Yakushima Island, Kagoshima Prefecture. Ari 30: 47-54.
 * Hung A. C. F. 1970. A revision of ants of the subgenus Polyrhachis Fr. Smith (Hymenoptera: Formicidae: Formicinae). Oriental Insects 4(1): 1-36.
 * Ito. F., Kondoh. M., Kubota. S., Masuko. K., Morishita. M., Murata. K., Ogata. K., Sato. T., Takamine. H., Yamaoka. H. and Kondoh. M. 1986. A list of ants collected at Akiyoshi-dai (Yamaguchi-ken) by the members of the Myrmecologists Society (Japan) in 1985. ARI Reports of the Myrmecologists Society (Japan) 14: 5-6
 * Kim B.J. 1996. Synonymic list and distribution of Formicidae (Hymenoptera) in Korea. Entomological Research Bulletin Supplement 169-196.
 * Kim B.J., K.G. Kim, J.H. Kim, S.J. Park. Ants from Mt. Mirok. Korean J. Soil Zoology 2(2): 115-128.
 * Kim C.H.; Choi, B.M. 1987. On the kinds of ants (Hymenoptera: Formicidae) and vertical distribution in Jiri Mountain. Korean Journal of Plant Protection 26:123-132.
 * Kim et al. 1993. Systematic study of ants from Chejudo Province. Koran Journal of Entomology 23(3): 117-141.
 * Kohout R. J. 2014. A review of the subgenus Polyrhachis (Polyrhachis) Fr. Smith (Hymenoptera: Formicidae: Formicinae) with keys and description of a new species. Asian Myrmecology 6: 1-31.
 * Kohriba, O. 1963. A parasitic life of Polyrhachis lamellidens F. Smith. First report. [In Japanese.]. Kontyû 31:207. [1963-09-30] PDF 126486
 * Kwon T. S. 2012. Korean ant atlas. Korea Forest Research Institute 162 pages.
 * Li Z.h. 2006. List of Chinese Insects. Volume 4. Sun Yat-sen University Press
 * Menozzi C. 1940. Contribution à la faune myrmécologique du Japon. Mushi. 13: 11-12.
 * Minato M., T. Kameyama, F. Ito, and T. Itino. 1996. A preliminary report of ant fauna in Gagawa Prefecture. Ari 20: 9-13.
 * Ogata. K., Touyama, Y. and Choi, B. M. 1994. Ant fauna of Hiroshima Prefecture, Japan. ARI Reports of the Myrmecologists Society (Japan) 18: 18-25
 * Paik W.H. 1984. A checklist of Formicidae (Hymenoptera) of Korea. Korean J. Plant Prot. 23(3): 193-195.
 * Park S. H., S. Hosoishi, K. Ogata, and Y. Kuboki. 2014. Clustering of ant communities and indicator species analysis using self-organizing maps. Comptes Rendus Biologies http://dx.doi.org/10.1016/j.crvi.2014.07.003
 * Park S.J., and B.J. Kim. 2002. Faunal comparison of ants among Cheongsando and other islands of South Sea in Korea. Korean Journal of Entomology 32(1): 7-12.
 * Park, Seong, Joon and Byung, and Kim, Jin. 2002. Faunal Comparison of Ants among Cheongsando and Other Islands of South Sea in Korea. Korean Jornal of Entomology. 32(1):7-12.
 * Radchenko, A. 2005. Monographic revision of the ants (Hymenoptera: Formicidae) of North Korea. Annales Zoologici (Warsaw) 55: 127-221.
 * Radchenko, A. 2005. Monographic revision of the ants (Hymenoptera, Formicidae) of North Korea. Annales Zoologici 55(2): 127-221.
 * Ran H., and S. Y. Zhou. 2013. Checklist of Chinese Ants: Formicomorph Subfamilies ( Hymenoptera: Formicidae) (III). Journal of Guangxi Normal University : Natural Science Edition 31(1): 104-111.
 * Robson Simon Database Polyrhachis -05 Sept 2014
 * Sakai H. 2002. Reproductive flight season of Japanese ants. Ari 26: 33-39.
 * 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.
 * Smith, F. 1874b. Descriptions of new species of Tenthredinidae, Ichneumonidae, Chrysididae, Formicidae, &c. of Japan. Transactions of the Entomological Society of London 1874:403-404
 * Smith, F. 1874b. Descriptions of new species of Tenthredinidae, Ichneumonidae, Chrysididae, Formicidae, &c. of Japan. Transactions of the Entomological Society of London 1874:404
 * Staab M., A. Schuldt, T. Assmann, H. Bruelheide, and A.M. Klein. 2014. Ant community structure during forest succession in a subtropical forest in South-East China. Acta Oecologia 61: 32-40.
 * Tang J., Li S., Huang E., Zhang B. and Chen Y. 1995. Hymenoptera: Formicidae (1). Economic Insect Fauna of China 47: 1-133.
 * Tang Jue, Li Shen, Huang Enyou, Zhang Benyue. 1985. Notes on ants from Zhoushan Islands Zhejiang (Hymenoptera: Formicidae).  Journal of Zhejiang University (Agric.& Life Sci.) 3.
 * 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. 2009. A synopsis of the family Formicidae of Taiwan (Insecta: Hymenoptera). Research Bulletin of Kanto Gakuen University. Liberal Arts 17:81-266.
 * 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., and S. Kubota. 2002. Ants of Tokyo, Japan. ARI 26: 1-32.
 * Terayama, M. 2009. A synopsis of the family Formicidae of Taiwan (Insecta; Hymenoptera). The Research Bulletin of Kanto Gakuen University 17: 81-266.
 * Teruyama. M. 1988. Ant fauna of Saitama Prefecture, Japan. ARI Reports of the Myrmecologists Society (Japan) 16: 4-13
 * Wang C. and Wu J. 1991. Taxonomic studies on the genus Polyrhachis of China (Hymenoptera: Formicidae). Forest Research 4: 596-601.
 * Wheeler W. M. 1921. Chinese ants. Bulletin of the Museum of Comparative Zoology 64: 529-547.
 * Wheeler W. M. 1929. Ants collected by Professor F. Silvestri in Formosa, the Malay Peninsula and the Philippines. Bollettino del Laboratorio di Zoologia Generale e Agraria della Reale Scuola Superiore d'Agricoltura. Portici 24: 27-64.
 * Wheeler W. M. 1930. A list of the known Chinese ants. Peking Natural History Bulletin 5: 53-81.
 * Wheeler W. M. 1930. Formosan ants collected by Dr. R. Takahashi. Proceedings of the New England Zoological Club 11: 93-106.
 * Yamane S., S. Ikudome, and M. Terayama. 1999. Identification guide to the Aculeata of the Nansei Islands, Japan. Sapporo: Hokkaido University Press, xii + 831 pp. pp, 138-317.
 * Yamane S., Y. Harada, and K. Eguchi. 2013. Classification and ecology of ants. Natural history of ants in Southern Kyushu. 200 pages
 * Yamane S.; Ikudome, S.; Terayama, M. 1999. Identification guide to the Aculeata of the Nansei Islands, Japan. Sapporo: Hokkaido University Press, xii + 831 pp. pp138-317.
 * Yoshimura M. 2009. Impact of secondary forest management on ant assemblage composition in the temperate region in Japan. J. Insect. Conservation 13(5): 563-568.
 * Zhou S.-Y. 2001. Ants of Guangxi. Guangxi Normal University Press, Guilin, China, Guilin, China. 255 pp.