Polyrhachis bihamata

Identification
Key to the subgenus Polyrhachis workers

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Brunei Darussalam, Indonesia, Philippines. Oriental Region: Laos, Myanmar, Thailand, Vietnam. Palaearctic Region: China.

Kohout (2014) - Polyrhachis bihamata has been recorded throughout Southeast Asia, from Vietnam, Laos, Thailand and Myanmar to Malaysia and south to Borneo, Sumatra, possibly Java and Bali. It was also listed by Fr. Smith (1858: 58; 1862: 39; 1863: 126; 1865: 69) variously from India, the Indonesian islands of Waigeo, Bacan, Seram and Sulawesi and from New Guinea, however, I believe that many of these records are based on misidentified specimens, representing mostly Polyrhachis olybria and/or Polyrhachis bellicosa and Polyrhachis erosispina.

Nomenclature

 *  bihamata. Formica bihamata Drury, 1773: 73, pl. 38, figs. 7, 8 (w.) MADAGASCAR (Johanna I.). [Locality in error, see Bolton, 1973b: 352.] Mayr, 1872: 139 (q.); Emery, 1887a: 238 (q.); Donisthorpe, 1942b: 70 (m.); Wheeler, G.C. & Wheeler, J. 1990b: 763 (l.). Combination in Polyrhachis: Smith, F. 1857a: 59. Senior synonym of affinis Le Guillou: Mayr, 1872: 139; Dalla Torre, 1893: 259; of minor Karavaiev, perplexa, tonsilis: Hung, 1970: 16; Kohout, 1998: 508.
 * affinis. Formica affinis Le Guillou, 1842: 314 (q.) BORNEO. [Unresolved junior primary homonym of Formica affinis Leach, 1825: 290.] Combination in Polyrhachis: Roger, 1863b: 7. Junior synonym of bihamata: Mayr, 1872: 139; Dalla Torre, 1893: 259.
 * perplexa. Polyrhachis (Polyrhachis) bihamata var. perplexa Santschi, 1925f: 92 (w.) LAOS. Junior synonym of bihamata: Hung, 1970: 16.
 * minor. Polyrhachis bihamata var. minor Karavaiev, 1927e: 12 (w.) INDONESIA (Java). [Unresolved junior primary homonym of minor Forel, above.] Junior synonym of bihamata: Hung, 1970: 16.
 * tonsilis. Polyrhachis (Polyrhachis) bihamata var. tonsilis Santschi, 1928h: 133 (w.) INDONESIA (Sumatra). Junior synonym of bihamata: Hung, 1970: 16.

Kohout (2014) - Polyrhachis bihamata was redescribed by Hung (1970: 16), who also proposed the synonymy of all three subspecific forms with the nominal species. Kohout (1998: 508) accepted Hung’s decision regarding the synonymy of P. bihamata perplexa but was hesitant to accept the synonymy of P. bihamata tonsilis. Similar to Santschi (1928), Kohout considered P. bihamata tonsilis to be an intermediate ‘form’, but between P. bihamata and P. olybria, rather than between P. bihamata and P. bellicosa. Kohout (1998) also examined the unique holotype of P. bihamata minor, described by Karavaiev from Java, and based on its similarity to P. bihamata tonsilis commented that “Judging from the available specimens, I believe that the synonymy of P. bihamata minor with P. bihamata tonsilis, and elevation of the latter to specific status could be justified”. However, the only available specimen besides the types is a topotypical individual (Sumatra, Sibolangit, 1919, J.A. Loerzing) and I am not prepared to make any nomenclatural changes without additional material. Consequently I have maintained the status quo and adopted Hung’s (1970) proposed synonymies.

Worker
Description by Kohout (2014).

Dimensions: TL c. 9.47 – 11.99; HL 2.17 – 2.77; HW 1.91 – 2.47; CI 81-94; SL 2.82 – 3.53; SI 133 – 149; PW 1.11 – 1.36; PeH 2.37 – 3.12; PeI 100-119; MTL 3.98 – 4.79 (19 measured).

Dimensions (bihamata perplexa syntypes): TL c. 10.84 – 12.45; HL 2.50 – 2.71; HW 2.25 – 2.37; CI 87 – 90; SL 3.17 – 3.53; SI 140 – 149; PW 1.16 – 1.26; PeH 2.92 – 3.12; PeI 113 – 119; MTL 4.33 – 4.84 (6 measured).

Dimensions (bihamata tonsilis syntypes): TL c. 10.08 – 10.73; HL 2.43 – 2.46; HW 2.15 – 2.21; CI 88 – 90; SL 3.12; SI 141 – 145; PW 1.06; PeH 2.77 – 2.87; PeI 114 – 117; MTL (missing) (2 measured).

Dimensions (bihamata minor holotype): TL c. 9.12; HL 2.21; HW 1.96; CI 89; SL (missing); PW 1.06; PeH 2.25; PeI 102; MTL 3.93.

Queen
Description by Kohout (2014).

Dimensions: TL c. 13.30; HL 2.77; HW 2.37; CI 85; SL 3.93; SI 166; PW 2.67; PeH 1.31; PeI 47; MTL 4.69 (1 measured).

Queen distinctly larger than worker and with usual characters identifying full sexuality, including three ocelli, complete thoracic structure and wings. The queen of P. bihamata was described by Mayr (1872) and the details are not repeated here. It is somewhat similar to queen of P. ypsilon, with both having the pronotal spines reduced to bluntly angular prominences. The mesoscutum in P. bihamata, however, is distinctly more slender and the golden pilosity and pubescence shorter and less abundant.

Male and immature stages in SMFG (Dr W.H.O. Dorow coll.); a single male in QMBA.