Rhopalomastix Forel, 1900

Wang, Wendy Y., Yong, Gordon W. J. & Jaitrong, Weeyawat, 2021, Revision of the elusive ant genus Rhopalomastix (Hymenoptera, Formicidae, Myrmicinae) in Thailand based on morphology and DNA barcodes, with descriptions of three new species, European Journal of Taxonomy 739 (1), pp. 117-157 : 120-123

Genus Rhopalomastix Forel, 1900

Rhopalomastix Forel, 1900: 24 .

Type species: Rhopalomastix rothneyi Forel, 1900 , by monotypy.

Rhopalomastix in Myrmicinae , Solenopsidini – Wheeler 1910: 140.

Rhopalomastix in Myrmicinae , Melissotarsini – Emery 1914: 40; 1922: 118. — Forel 1917: 242. — Wheeler 1922: 661. — Bolton 2003: 72.

Rhopalomastix in Myrmicinae , Crematogastrini – Ward et al. 2015: 71, 77.

For diagnosis of the workers in the genus Rhopalomastix , refer to Bolton (2003) and Wang et al. (2018b). For diagnoses of the queen and male of the same genus, see Wang et al. (2018b).

Synoptic list of species in Thailand

Rhopalomastix impithuksai Wang & Jaitrong sp. nov.

Rhopalomastix javana Wheeler, 1929

Rhopalomastix johorensis Wheeler, 1929

= Rhopalomastix janeti Donisthorpe, 1936

Rhopalomastix parva Wang & Jaitrong sp. nov.

Rhopalomastix robusta Wang & Jaitrong sp. nov.

Key to Thai species based on the worker caste

1. External face of mandible other than narrow strip next to masticatory margin with distinct striations ( Fig. 2a–b ); extent and intensity of striations variable. Median clypeal area carinulate, supraclypeal area with dark-pigmented longitudinal carinae ................................................................................ 2

– External face of mandible other than narrow strip next to masticatory margin largely smooth and shiny ( Fig. 2c–e ). Median clypeal area and supraclypeal area with varying forms of sculpture but never with multiple dark-pigmented longitudinal carinae ................................................................ 3

2. Striations on dorsum of head uniformly dense from frontal lobes to posterior margin; relatively large species (TL 2.24–3.16), total length of smallest worker> 2 mm. Large worker with head blackish brown, and either as long as wide or wider than long (CI 100–103) .................................................. ................................................................................................... R. robusta Wang & Jaitrong sp. nov.

– Striations on dorsum of head weaker and more fragmented in posterior half; relatively smaller species (TL 1.84–2.93), total length of smallest worker <2 mm. Worker (of all sizes) with head dark brown, but never blackish, always longer than wide (CI 94–96) ....................................................... ............................................................................................ R. impithuksai Wang & Jaitrong sp. nov.

3. Head distinctly much longer than wide (CI 84–87); anterior margin of pronotal disc (excluding the collar) strongly convex with roundly angulate median point. Relatively small species (TL 1.85– 2.25) ............................................................................................. R. parva Wang & Jaitrong sp. nov.

– Head not distinctly longer than wide (CI 87–96); anterior margin of pronotal disc (excluding the collar) broadly and often weakly convex with no angular median point ......................................... 4

4. Propodeal junction in lateral view distinct and roundly obtuse; propodeal dorsum differentiated from posterior declivity by weakly marginate angular edge. Posterolateral corner of propodeal dorsum angulate; posterior propodeal face overall weakly marginate. Anterior clypeal face in profile weakly and broadly convex ..................................................................................... R. javana Wheeler, 1929

– Propodeal junction in lateral view indistinct and broadly rounded, propodeal dorsum rounding smoothly into and not differentiated from posterior declivity by marginate angular edge. Posterolateral corner of propodeal dorsum usually indistinct, sometimes bluntly and shallowly rounded; posterior propodeal face overall incompletely marginate with obscure dorsal edge. Anterior clypeal face in profile mostly flat or weakly and broadly convex ................................ R. johorensis Wheeler, 1929

Figures

Fig. 2. Closeups of external mandibular surface for workers of 5 Thai species of Rhopalomastix Forel, 1900 (ZRC); white arrows indicate distinct striations on the external mandibular face. a. R. impithuksai Wang & Jaitrong sp. nov., paratype (ZRC_ENT00007608). b. R. robusta Wang & Jaitrong sp. nov., paratype (ZRC_ENT00013949). c. R. javana Wheeler, 1929, non-type (ZRC_ENT00000932). d. R. johorensis Wheeler, 1929, non-type (ZRC_ENT00007874). e. R. parva Wang & Jaitrong sp. nov., paratype (ZRC_ENT00013948).