Tetraponera extenuata

Two nest series from Singapore are from dead twigs of Timonius sp. and Rhodamnia trinervia, respectively. Most other collections consist of foraging workers on low vegetation or specimens taken in fogging samples. (Ward 2001) Heterick & Kitching (2022) collected this species in the canopy of a lowland dipterocarp forest in Brunei.

Identification
A member of the Tetraponera allaborans species-group.

Ward (2001) - This species is superficially similar to small specimens of Tetraponera allaborans, especially those in which the appendages and postpetiolar node are lighter in color than the rest of the body. However, workers of T. extenuata can be consistently separated from those of T. allaborans by the taller and more slender propodeum. In addition the pronotal margins are more convex (dorsal view) and soft-edged than in most T. allaborans, and the maximum width of the pronotum occurs at the pronotal margins, not below the margins as in many T. allaborans.

More problematic is the relationship of T. extenuata to Tetraponera modesta. These two are rather similar with respect to the shapes of the pronotum, propodeum and petiole. T. extenuata averages larger in size and is much darker in coloration than “typical” orange-yellow T. modesta. Moreover, in T. extenuata workers there is usually a strong contrast between the dark body and orange-brown postpetiole, and between the dark brown femora and pale yellow (or cream) tibiae. But color is variable, and in some workers of T. extenuata from Borneo (Sabah) and the Philippines the postpetiole is dark brown and does not contrast with the rest of the body. In these individuals the legs are nevertheless conspicuously bicolored. Conversely, in a series of workers from Kintamani, Bali (leg. Dorow), tentatively identified as T. extenuata, the postpetiole exhibits a contrasting orange-brown color, but the legs are uniformly dark brown! Many samples of T. extenuata consist of relatively large workers (HW >0.65) and these can be separated from T. modesta by size alone. But workers at the lower size limit of T. extenuata (HW 0.54-0.65) can be difficult to distinguish from some samples of T. modesta, in which there is a darkening of the integument.

Distribution
Found from Thailand and peninsular Malaysia east to the Philippines and south to the lesser Sundas (Bali and Lombok).

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

Habitat
Habitats from which it has been recorded include primary and secondary growth lowland rainforest (Singapore, Borneo, Luzon), lower montane mixed dipterocarp forest (Borneo), and “relict rainforest” (Mindanao).

Nomenclature

 *  extenuata. Tetraponera extenuata Ward, 2001: 614, figs. 16, 27, 33, 39, 50 (w.q.) SINGAPORE.

Worker
HW 0.54-0.79, HL 0.70-0.95, LHT 0.45-0.74, CI 0.76-0.87, FCI 0.08-0.13, REL 0.36-0.41, REL2 0.44-0.51, SI 0.60-0.65, SI3 1.18-1.43, FI 0.38-0.43, PLI 0.47-0.59, PWI 0.38-0.48, PDI 1.12-1.24, LHT/HW 0.84--0.94, CSC 1-2, MSC 3-4.

Small to medium-sized species; median clypeal lobe narrow, distinctly set off from the rest of the clypeal margin, and furnished with three weak denticles (sometimes effaced); anterior margin of clypeal lobe variably extended, often rather short and not exceeding the reach of the anterolateral clypeal margins, but more protruding in some workers; profemur slender; lateral margins of pronotum soft-edged, convex in dorsal view, and corresponding to the maximum width of pronotum; mesopropodeal impression well developed, longitudinally rugulate, and lacking metanotal plate; propodeum high and narrow, such that PDI > 1.10; petiole relatively slender (see PLI and PWI values). Integument smooth and shiny, with scattered fine punctures (c. 0.01 mm diameter) and fine irregular lineations; malar area longitudinally carinate, such sculpture usually covering less than half the distance between the mandibular insertions and the lower margin of the compound eye; a few weak longitudinal carinulae may be present on the mesopleuron, metapleuron and side of propodeum. Standing pilosity sparse; long standing hairs (>0.06 mm) present on gaster and apex of head and as follows: one supraocular pair, two pairs on pronotum, 0-1 pair on petiole and 0-1 pair on postpetiole; shorter appressed and subdecumbent hairs scattered over body, tending to becoming suberect ventrally, especially on petiole and postpetiole. Typically black or dark brownishblack, with contrasting lighter (yellow or orange-brown) postpetiole, tibiae, tarsi, and scapes; lighter coloration may also extend to the petiole, base of abdominal tergite IV, profemur, frontoclypeal complex and mandibles.

Type Material
Holotype. Worker, Bukit Timah, Singapore, 100 m, 1°21'N 103°47'E, 20.xi.1988 (P. S. Ward #9570). Paratypes. Series of workers, 1 dealate queen, same data as holotype (, KUBC,, KUES, , , RMBR, , , ).

References based on Global Ant Biodiversity Informatics

 * Pfeiffer M.; Mezger, D.; Hosoishi, S.; Bakhtiar, E. Y.; Kohout, R. J. 2011. The Formicidae of Borneo (Insecta: Hymenoptera): a preliminary species list. Asian Myrmecology 4:9-58
 * Ward P. S. 2001. Taxonomy, phylogeny and biogeography of the ant genus Tetraponera (Hymenoptera: Formicidae) in the Oriental and Australian regions. Invertebrate Taxonomy 15: 589-665.
 * Ward, P. S. 2001. Taxonomy, phylogeny and biogeography of the ant genus Tetraponera (Hymenoptera: Formicidae) in the Oriental and Australian regions. Invertebrate Taxonomy 15:589-665.