Tetramorium flagellatum

Collection records note montane forest collections from a rotten log and a litter sample.

Identification
Sorger (2011) - Differentiation between Tetramorium lucyae and T. flagellatum is difficult, and careful examination and measurements are necessary in order to successfully and reliably identify these species.

There are three distinguishing characters: maximum hair length (on head, mesosoma and tibiae), frons sculpture and total length (although the latter can be used only with a larger nest sample: at least 20 specimens). None of these characters should be used for identification in isolation; only a combination of all characters provides a clear picture of the distinctions between the species. A combination of MHLH, MHLM and MHLT is vital for identification; in addition, it is recommended to use a nest sample of more than 5 specimens where possible, given variation among individuals.

All measurements are in millimetres and presented as minimum-mean-maximum values.

Maximum hair lengths on head, mesosoma and tibiae: T. lucyae (0.40–0.48–0.59 MHLH; 0.46–0.51–0.58 MHLM; 0.22–0.30–0.34 MHLT) has longer hairs than T. flagellatum (0.30–0.35–0.40 MHLH; 0.34–0.41–0.44 MHLM; 0.10–0.17–0.22 MHLT) overall. Two single specimens in the studied sample overlap at a single value each: (MHLT: 0.40 mm; MHLT: 0.20 mm).

Frons sculpture: Sculpture on head frons is more longitudinally oriented in T. flagellatum. However, this differential character is subtle—longitudinal rugae on frons (right at medial depression) are more irregular (“shaky”) in T. lucyae whereas, in comparison, rugae are rather straight in T. flagellatum.

Total length: T. flagellatum (3.28–3.55–3.80 TL) is smaller than T. lucyae (3.60–3.73–3.86 TL) overall. However, since the mean TL of T. lucyae lies within the overlapping range (3.60 to 3.80 mm TL) of the two species, a nest series of at least 20 specimens is necessary in order to calculate a mean value.

Bolton (1977) - The outstanding long pilosity and its distribution on the appendages immediately characterize this exceptional species. It shows relationship with Tetramorium ciliatum of Thailand and Vietnam and also with Tetramorium tylinum, also of Borneo. However, neither of these species has the remarkable pilosity of Tetramorium flagellatum. A further specimen of this species, from Borneo, agrees perfectly with the description but the head and alitrunk are a much lighter brown than in any of the type-series.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Indonesia, Malaysia.

Nomenclature

 *  flagellatum. Tetramorium flagellatum Bolton, 1977: 122, fig. 48 (w.) BORNEO. See also: Sorger, 2011b: 5.

Worker
Holotype. TL 3.9, HL 0.90, HW 0.82, CI 91, SL 0.66, SI 80, PW 0.62, AL 1.04.

Mandibles striate; anterior clypeal margin entire. Frontal carinae reaching back almost to occiput but irregular, and in their posterior halves only as strongly developed as the other cephalic sculpture. Antennal scrobes long and broad but shallow, easily discernible. Eyes in front of middle of sides of head, maximum diameter c. 0·18. Sides of head weakly convex, the occipital margin broadly concave in full-face view. Propodeal spines elevated, of moderate length, feebly upcurved and acute apically. Metapleural lobes triangular basally, spiniform and acute apically. Node of petiole in profile with the dorsal length greater than the height of the tergal portion; postpetiole narrowly dome-like. In dorsal view the petiole node slightly broader than long. Dorsal surfaces of head, alitrunk, petiole and postpetiole covered with a distinct, irregular rugulation, reticulate in places and finer and denser on the head than on the alitrunk. Gaster unsculptured. All dorsal surfaces of head and body with numerous exceptionally long, very conspicuous fine hairs, the majority of which are curved (Fig. 48). The longest of these hairs measure 0.45-0.50, well over half the length of the scape. Long, erect hairs present on dorsal (outer) surfaces of hind tibia which are longer than the maximum tibial width but such hairs absent from the scapes where all hairs are shorter than the maximum width of the scape and fine. Colour uniform dark brown, the appendages yellowish.

Paratypes. As holotype but many not showing any apical upcurvature in the propodeal spines, which in some paratypes are also more strongly acute apically. Size range of paratypes TL 3.6-4.2, HL 0.88-0.98, HW 0.80-0.90, CI 90-95, SL 0.62-0.70, SI 75-80, PW 0.60-0.68, AL 1.02-1.16 (6 measured).

Maximum diameter of eye in paratypes c. 0.18-0.20.

Sorger (2011) - Measurements of workers (range of 20 workers). Worker with smallest HW: HW 0.71; HL 0.76; CI 93; SL 0.57; SI 80; PW 0.52; ML 0.92; TL 3.34; MHLH 0.36; MHLT 0.17; MHLM 0.41. Worker with largest HW: HW 0.83; HL 0.90; CI 92; SL 0.64; SI 77; PW 0.62; ML 1.08; TL 3.80; MHLH 0.33; MHLT 0.19; MHLM 0.44. Mean values of 20 workers: TL 3.55; MHLH 0.35; MHLT 0.17; MHLM 0.41.

Type Material
Holotype worker, Borneo: N., Kiduk Arok, Trus Madi Massif, 1500 m, ix.1956, Cambridge N. Borneo Exped. no. 49 (P. W. Bryant). Paratypes. 5 workers with same data as holotype and 1 worker with same data but no. 78 (MCZC; ).