Rhopalomastix robusta

This species is thus far only known from its type series, collected from relatively good secondary forest at moderately high elevation (927 m). The colony was found in bark of a large dipterocarp tree, Toona ciliata, located near the edge of the forest. Members of the colony seemed rather gregarious when found, with numerous individuals moving quickly en masse as a collective group to seek cover when exposed upon removal of a bark layer.

Identification
Smaller workers of R. robusta are similar to large workers of both Rhopalomastix impithuksai and Rhopalomastix johorensis. The first two species can be differentiated by the following:
 * 1) striations on dorsum of head uniformly dense from frontal lobes to posterior margin in R. robusta, but in R. impithuksai, striations on head dorsum are weaker and more fragmented in posterior half
 * 2) outline of clypeus in lateral view–entirely flat or weakly convex with no angulate edge in R. robusta, but with short weakly convex dorsal face separated from steep and almost flat anterior face by a weak angulate edge in R. impithuksai
 * 3) head in full-face view as long as wide or sometimes wider than long for R. robusta, whereas for R. impithuksai, head in fullface view always longer than wide
 * 4) median furrow on head dorsum starting from between frontal lobes quite long and relatively deep in R. robusta, either extending till or past transverse midline of head, in R. impithuksai the median furrow is shorter, usually narrower and shallower in its posterior half, often fading out before transverse midline of head.

Points (3) and (4) can also be used to distinguish between R. robusta (small workers) and R. johorensis (large workers).

Distribution based on Regional Taxon Lists
Oriental Region: Thailand.

Nomenclature

 * . Rhopalomastix robusta Wang & Jaitrong, in Wang et al., 2021: 150, figs. 2b, 13, 14, 15, 16a (w.) THAILAND.