Ectomomyrmex leeuwenhoeki (Forel, 1896)

Ectomomyrmex leeuwenhoeki (Forel, 1896) View in CoL

Material examined. Worker and queen, Bukit Timah Nature Reserve , 1.34772, 103.77766, 30 Nov 2015, M.K.L. Wong leg., ZRC _ ENT00000711-712 View Materials GoogleMaps ; same locality as previous, plot II-I, 15 Aug 2011, J. Koh leg., Winkler extraction, ZRC _ ENT00000888 View Materials GoogleMaps ; same locality as previous, BT04, 1.35342, 103.7782, 19 Jan 2017, W. Wang leg., WW-SG17-010, ZRC GoogleMaps _ HYM_0000583; queen, same locality and collector as previous, near BT02, 1.35599, 103.77397, 8 Aug 2017, ZRC GoogleMaps _ HYM_0001746; queen and worker, same locality and collector as previous, near BT01, 7 Jun 2017, ZRC _ ENT00014153 View Materials GoogleMaps ; same locality and collector as previous, BT09, 1.35127, 103.78161, 5 Jul 2017, ZRC _ ENT00014154 View Materials GoogleMaps ; Central Catchment Nature Reserve , 16 Feb 2016, G.W. Yong leg., ZRC _ ENT00047846 View Materials ; same locality as previous, 10 Aug 2011, E.J.Y. Soh leg., ZRC _ ENT00048001 View Materials ; Lower Peirce Reservoir , 7 May 2017, G.W. Yong leg., ZRC _ ENT00048420 View Materials ; same locality as previous, Forest B, 10 Aug 1990, collector unknown, ZRC _ ENT00000205 View Materials ; same locality as previous, Forest A, 7 Aug 1990, collector unknown, ZRC _ ENT00000127 View Materials ; Mandai Lake Road, Northern Node , 1°24’36.5”N, 103°47’04.0”, 18 Jul 2019, J.S. Tan & N.L. Chin leg., Winkler extraction, ZRC _ ENT00028287-28288 View Materials ; Mandai Road , 1.41054, 103.79809, 5 Dec 2016, G.W. Yong et al. leg., M1D5GH2474, ZRC _ ENT00047845 View Materials GoogleMaps ; queen and worker, Nee Soon Swamp Forest , 1.38252, 103.80208, 25 Sep 2017, W. Wang leg., NS_W1, Winkler extraction, ZRC _ ENT00027909 View Materials GoogleMaps ; same locality as previous, dry plot 301, 1.38043, 103.8033, 22 Aug 2019, W. Wang leg.,WW-SG19-002, ZRC _ ENT00013872 View Materials GoogleMaps ; alate queens and males, same location as previous, 2012-2013, J. Puniamoorthy et al. leg., malaise trap, ZRC GoogleMaps _BDP (multiple).

Material not physically examined. Unknown.

Literature. Viehmeyer (1916), Overbeck (1924) [both as Pachycondyla (Ectomomyrmex) leeuwenhoeki ].

Localities. Bukit Timah Nature Reserve; Bukit Timah Road; Central Catchment Nature Reserve; Lower Peirce Reservoir; Mandai Lake Road; Mandai Road; Nee Soon Swamp Forest.

Habitat/Ecology. This species is associated mostly with primary or old/mature secondary forests in Singapore, including swamp forest (drier sections). The ants have also been found in abandoned plantation and native-dominated secondary forests. Nests were found in soil substrate matrices under dead wood, also in rotting wood or branches on forest floors. Individuals were often collected from leaf litter and in soil at bases of living trees.

Remarks. Amongst material examined for E. leeuwenhoeki , we observed substantial variation across different samples of workers. These variable features include: petiole shape (wider and shorter in dorsal view for some individuals), strength of sculpture on petiolar node (fovea generally weaker in some individuals), and relative dimensions of head. Variation, however, is subtle and can occur between intranidal workers, which sometimes present a gradation of intermediate morphological states.

Some of the variable states we observed are apparently diagnostic, according to original descriptions, for the two subspecies of E. leeuwenhoeki – E. leeuwenhoeki jacobsoni ( Forel, 1915) and E. leeuwenhoeki sumatrensis (Forel, 1901) . But these traits seem too unstable, at least based on local samples, to reliably differentiate between E. leeuwenhoeki and its subspecies.

At the time of writing, we are unable to assess the validity of both subspecies – no access to type material including type images of jacobsoni – against E. leeuwenhoeki . For now, we choose to err on the side of caution and refrain from making definitive conclusions on species status for the two forms. It remains possible that the two subspecies might be synonymized under E. leeuwenhoeki , provided more compelling evidence over a wider geographic range arises in future.