Technomyrmex brunneus

In Japan this species forms huge polydomous colonies that can contain millions of workers.

Identification
Bolton (2007) - A member of the T. albipes complex in the Technomyrmex albipes group. T. brunneus is easily distinguished from Technomyrmex albipes, and all other former infraspecific taxa and synonyms that were attached to albipes, by its possession of a longitudinal groove on the mandible and relatively posteriorly located eyes. The presence of a mandibular groove is shared only with Technomyrmex mandibularis of Malaysia, which also has the eyes located posteriorly, but mandibularis has an unsculptured, highly polished head capsule, a row of short erect setae on the dorsal surface of the scape and numerous setae on the dorsum of the head behind the level of the posterior margin of eyes, all of which are absent from brunneus.

Distribution
Bolton (2007) - The distribution of brunneus is Oriental. Its distribution in Japan is illustrated in Imai, Kihara, Kondoh, et al. (2003). The discovery of a single specimen from Brunei, apparently without the species being present in intervening states, is anomalous and the record probably represents an introduction or perhaps a mislabeling of the specimen.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Indonesia, Malaysia, New Guinea. Oriental Region: India, Taiwan. Palaearctic Region: China.

Biology
This species is widely distributed in the Oriental region proper and is quite common in parts of China, Taiwan and Japan. It is certainly the species described and illustrated as albipes by lmai, Kihara, Kondoh, et al. (2003) and Zhou (2001), and is probably the species included as albipes by Wu & Wang (1995), although the latter's sketch is quite crude. It is certainly the species intensively studied in Japan by Tsuji, Furukawa, et al. (1991), Yamauchi, Furukawa, et al. (1991), Tsuji & Yamauchi (1994) and Ogata, Murai et al. (1996).

Yamauchi, Furukawa, et al. (1991) say that this species in Japan forms huge polydomous colonies that may contain millions of adults. It often nests in dead standing trees and has a complex reproductive system. New nests are begun by recently dealate queens, following a nuptial flight with alate males, as is usual in ants. The newly established fecund queen produces large numbers of workers and about an equal number of ergatoid queens that are morphologically intermediate, in varying degrees, between workers and winged queens. She also produces wingless (ergatoid) males, which mate with the ergatoid queens and produce offspring of both sexes and all castes. Eventually the foundress queen dies and reproductive behaviour is continued only by the ergatoid queens and the ergatoid males. Ergatoid queens do not conduct foraging activities and are not found outside nests, and nests in this condition may undergo fission and bud off new colonies. In the fullness of time the ergatoid queens and ergatoid males produce new generations of alate queens and alate males, to complete the cycle.

There appears to be no trophallaxis in this species and nutrient transfer is achieved entirely by the distribution of trophic eggs, which are produced by all the female castes including the workers. This does not correspond to the situation in Technomyrmex difficilis, where trophallaxis appears to be present (Warner, 2003).

Yamane et al. (2018) - Although Bolton (2007) resolved most taxonomic confusion in this species group, there still remain some unsolved problems. For example, very restricted information is available about the nesting habits of T. albipes in spite of its common occurrence as a tramp. Bolton enumerated a few instances for the nesting site of this species, namely, internodes of a myrmecophyte, plant spathes and rot holes in wood. However, some carton nests on tree leaves have been found in Borneo and Malay Peninsula for ‘this species’ as well as nests in restricted spaces such as rotting wood, dead twigs etc. (Yamane and Tsuji, personal obs.). This suggests that T. albipes (sensu Bolton) may actually be a complex of sibling species. More information on nesting site and DNA data from various localities are needed to resolve this problem.

Castes
Tsuji, Furukawa, et al. (1991) analysed the female intercastes and found that all had spermathecae, which were absent from genuine workers. These intercastes correspond to the ergatoid queens (flightless) described throughout Formicidae. They were able to distinguish three distinct morphological intercastes (major, medium and minor) between fully developed queens and true workers, based on number of ocelli present and the degree of development of the mesosoma. Most intercastes were inseminated and had developed ovaries, and the number of ovarioles increased with body size from minor to major. Alate queens had a larger body size, far more ovarioles and larger spermathecae than the largest ergatoid queens.

Nomenclature

 *  brunneus. Technomyrmex albipes r. brunneus Forel, 1895e: 467 (w.) INDIA. Raised to species: Bingham, 1903: 302. Subspecies of albipes: Emery, 1913a: 43. Revived status as species: Bolton, 2007a: 73. Senior synonym of angustior: Bolton, 2007a: 73.
 * angustior. Technomyrmex modiglianii var. angustior Forel, 1912a: 71 (w.) TAIWAN. Junior synonym of brunneus: Bolton, 2007a: 73.

Worker
Bolton (2007) - TL 2.4 - 2.8, HL 0.62 - 0.72, HW 0.59 - 0.69, SL 0.50 - 0.64, PW 0.43 - 0.47, WL 0.75 - 0.86 (30 measured). Indices: CI 90 - 97, SI 91 - 98, OI 23 - 27, EPI 112 - 136, DTI 109 - 119.

Basal half of mandible with a longitudinal groove on the dorsal surface close to the outer margin. Frontal carina with 2 (very rarely 3) setae: in profile the posteriormost seta close to or at the level of the anterior margin of the eye. Dorsum of head posterior to this entirely lacks setae. With head in full-face view the anterior clypeal margin with a minute median indentation. Sides of head convex. Eyes located at or just behind the midlength, EPI > 100; outer margin of eye touches, or usually just breaks, the outline of the side. With mesosoma in profile the mesonotal outline is evenly curved, without a distinct step or angle in the outline that defines conspicuous dorsal and declivitous faces. Proprodeal dorsum and declivity meet in an angle; straight-line length of propodeal dorsum in profile is less than depth of declivity to the spiracle. Number of setal pairs on mesosoma: pronotum 1 - 3 (usually 2); mesonotum 1; propodeal dorsum 0; lateral margin of propodeal declivity 1. Gastral tergites 1 - 4 each with numerous setae, distributed everywhere on the sclerites; maximum length of setae on first gastral tergite is usually slightly less than the maximum diameter of the eye but sometimes the two are subequal. Head, mesosoma, petiole and gaster blackish brown to black. Coxae, femora and tibiae uniformly blackish brown to black, same colour as the mesosoma or gaster; never with strongly contrasting lighter coxae. Tarsi of middle and hind legs yellowish white to dull yellow, much paler than the tibiae.

Type Material
Bolton (2007) - Holotype worker, India: Poona, 11/9, 1901 (Wroughton) [examined].

The holotype of brunneus, as well as being the most westerly individual seen of this species, is also the palest in colour, with a medium brown head and mesosoma and a blackish brown mottled gaster. I strongly suspect that the specimen had not attained full adult colour when captured as it matches some immature workers included in a sample from Kyushu.