Tetraponera crassiuscula

A collection from Kepong, Malaysia (leg. Maschwitz) was made from twigs of Rhizophoraceae. A worker from Umas Umas, Borneo was taken “ex trunks, tops, recently felled trees, rainforest”.

Identification
A member of the Tetraponera allaborans species-group.

Ward (2001) - Tetraponera crassiuscula belongs to a group of closely related taxa, here termed the T. modesta-complex. Three morphotypes can be tentatively recognised: T. crassiuscula, a dark brown form with a short, broad petiole (worker PLI 0.60-0.68); Tetraponera modesta, a smaller, yellow or orange-brown species, with more slender petiole (PLI 0.45-0.59); and Tetraponera extenuata, similar to T. modesta but with relatively large, mostly black workers. Sympatric associations of at least two of the three forms are known from some localities (Bukit Timah, Singapore: T. extenuata and T. modesta; Pasoh Forest, Malaysia: T. crassiuscula, T. extenuata and T. modesta; Poring Spring, Malaysia: T. extenuata and T. modesta), suggesting that they represent good species. Not all collections can be easily assigned to one of these three taxa, however.

Distribution
T. crassiuscula is known from Thailand, peninsular Malaysia, Sumatra, and Borneo.

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

Nomenclature

 *  crassiuscula. Sima allaborans subsp. crassiuscula Emery, 1900d: 677, fig. 6 (w.) INDONESIA (Sumatra). Combination in S. (Tetraponera): Viehmeyer, 1916a: 117; Emery, 1921f: 25; in Tetraponera: Crawley, 1924: 390; Chapman & Capco, 1951: 78. Raised to species: Ward, 2001: 611.

Worker
Ward (2001) - HW 0.53-0.61, HL 0.66-0.73, LHT 0.45-0.52, CI 0.73-0.84, FCI 0.08-0.11, REL 0.36-0.40, REL2 0.46-0.50, SI 0.60-0.66, SI3 1.24-1.36, FI 0.40-0.43, PLI 0.60-0.68, PWI 0.46-0.54, PDI 1.14-1.26, LHT/HW 0.81-0.91, CSC 1-10, MSC 1-19.

Small species; median clypeal lobe narrow but moderately prominent, furnished with three blunt denticles; anterior margin of clypeal lobe slightly exceeding the reach of the anterolateral margins of the clypeus; profemur slender; lateral margins of pronotum soft-edged, convex in dorsal view, and corresponding to the maximum width of pronotum; mesopropodeal impression deep but somewhat short (from anterior to posterior ends), lacking metanotal plate; propodeum high and narrow, such that PDI > 1.12; petiole relatively short, with a prominent node (PL 0.38-0.46, PLISL 1.09-1.19; see also PLI and PWI values). Integument smooth and shiny, with scattered fine punctures (c. 0.01 mm diameter) and fine irregular lineations; lower malar area longitudinally carinate; weak carinulae variably developed (may be absent) on side of posterior mesosoma. Pilosity variable (MSC 1-19), but tending to be more common than in related taxa; some workers with four or more standing hairs (>0.05 mm in length) visible in profile on each of the following: dorsum of head, pronotum, mesonotum, petiole and postpetiole; such setae grading into shorter decumbent and appressed hairs; in other specimens standing pilosity much sparser (or abraded). Dark brown, with lighter brown petiole, postpetiole, pronotum and appendages; legs concolorous medium brown.

Type Material
Ward (2001) - Syntypes, 2 workers, D. Tolong, Sumatra, Indonesia (E. Modigliani).

References based on Global Ant Biodiversity Informatics

 * Chapman, J. W., and Capco, S. R. 1951. Check list of the ants (Hymenoptera: Formicidae) of Asia. Monogr. Inst. Sci. Technol. Manila 1: 1-327
 * Crawley W.C. 1924. Ants from Sumatra, with biological notes by Edward Jacobson. Annals and Magazine of Natural History (9)13: 380-409
 * Emery C. Formiche raccolte da Elio Modigliani in Sumatra, Engano e Mentawei. Annali del Museo Civico di Storia Naturale 40: 661-722.
 * Emery, C. "Formiche raccolte da Elio Modigliani in Sumatra, Engano e Mentawei." Annali del Museo Civico di Storia Naturale Giacomo Doria (Genova) (2) 20, no. 40 (1900): 661-722.
 * Jaitrong W.; Nabhitabhata, J. 2005. A list of known ant species of Thailand. The Thailand Natural History Museum Journal 1(1): 9-54.
 * 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.