Rhopalomastix johorensis Wheeler, 1929

Material examined. Syntypes of ‘ R. rothneyi subsp. johorensis ’ – no specific locality given, MCZ-ENT00023066 (MCZ). Non-types – Bukit Timah Nature Reserve, 1.35127, 103.78161, 1 Nov 2017, W. Wang leg., WW-SG17-022, ZRC _HYM_0001794; Hougang Avenue 3, 1.34769, 103.88838, 12 Dec 2016, G.W. Yong & S.X. Chui leg., GY-SG16- RhoL, ZRC _HYM_0000511; male, I-cube building (NUS), 1.293472, 103.77633, 24 Mar-1 Apr 2015, M.S. Foo & W. Wang leg., malaise trap, NUS0002, ZRC _ BDP0044708; Lee Kong Chian Natural History Museum (NUS), side yard, 24 Aug 2018, G.W. Yong leg., WW-SG18- Rho 1, ZRC _ ENT00007463; queens and workers, Mandai Road, 1.41445, 103.79831, 4 Oct 2018, G.W. Yong & W. Wang leg., WW-SG18-RhoMA, ZRC _ ENT00007519 ; males and workers, Mandai Road, 1.41333, 103.79839, 18 Nov 2016, G.W. Yong & S.X. Chui leg., GY-SG16-RhoF, ZRC _HYM_0000289; queen and workers, Mandai Road, 1.41318, 103.79405, 21 Nov 2016, G.W. Yong and S.X. Chui leg., GY-SG16-RhoH, ZRC _HYM_0000291; same locality as previous, 13 Jan 2017, G.W. Yong leg., GY-SG17-RhoO, ZRC _HYM_0000577; queens and workers, Mandai forest, near Zoo, 15 Jan 2020, W. Wang leg., WW-SG20-005 – 006, ZRC _ ENT00027891-27892 ; Nee Soon Swamp Forest, 24 Sep 2019, W. Wang leg., WW-SG19-005, ZRC _ ENT00013876 ; queen and workers, Pulau Tekukor, 1.23081, 103.83774, 15 Jan 2017, G.W. Yong leg., GY-SG17-RhoP, ZRC _HYM_0000578; male, Pulau Ubin, PU 1, 1°24’36.3”N, 103°59’25.5”E, 1-8 Sep 2012, J. Puniamoorthy et al. leg., mangroves, malaise trap, Reg. 29449, ZRC _ BDP0014267; male, Pulau Semakau Old Fragment, SMO3, 1°12’23.9”N, 103°45’37.6”E, 17-25 Oct 2012, J. Puniamoorthy et al. leg., mangroves, malaise trap, Reg. 29539, ZRC _ BDP0014651 ; queens and workers, Upper Seletar Reservoir Park, 14 Feb 2018, G.W. Yong leg., GY-SG18- Rho 1, ZRC _ ENT00000897 .

Material not physically examined. CASENT0911229, ANTC33476 (MHNG) [headless worker].

Literature. Viehmeyer (1916), Overbeck (1924) [both as Rhopalomastix rothneyi Forel, 1900 – verified as R. rothneyi johorensis by Wheeler (1929)]. Wheeler (1929) [as R. rothneyi johorensis]. Wang et al. (2018c); Wang et al. (2021).

Localities. Bukit Timah Nature Reserve; Bukit Timah Road; Hougang; National University of Singapore campus (Clementi/Kent Ridge, multiple sites); Mandai Road; Mandai forest near Singapore Zoo; Nee Soon Swamp Forest; Pulau Tekukor; Pulau Semakau; Pulau Ubin; Upper Seletar Reservoir Park.

Habitat/Ecology. Rhopalomastix johorensis appears ubiquitious locally and could be found in a broad range of different habitat types, including urban or semi-urban habitats (such as roadside vegetation), parks and gardens, old/mature and native-dominated secondary forests, and swamp forests. The ants nest in bark of various trees, both native species such as: Aquilaria malaccensis, Artocarpus integer (cempedak), Campnosperma auriculatum, Macaranga gigantea, Horsfieldia sparsa, and also introduced tree species such as Mangifera indica (mango). Nests have also been found in dead ends of twigs of cultivated mangosteen trees, and in bark of durian trees. Multiple nests (one nest per tree) can occur at relatively high densities per site where the species occurs — these are probably independent colonies and not satellites of a larger super-colony. The species appears tolerant to high levels of habitat disturbance. Males were collected from malaise traps set up in mangroves.

Remarks. Type locality in Singapore. As with many congeners, this species is known to exhibit very broad intranidal, generally isometric size variation.