Rhopalomastix

Rhopalomastix workers chew a network of tunnels under the bark of living trees, and tunnels are inhabited by large numbers of diaspidid scale insects (Yong et al. 2019). In SIngapore, second ant genus to be associated with diaspidids, besides Melissotarsus. Rhopalomastix chews tunnels in live wood and forms non-specific mutualisms with different genera of diaspidids.

Eguchi, Bui and Yamane (2011) - The worker of Rhopalomastix is easily separated from those of other known Vietnamese myrmicine genera by a combination of the following characters: frontal lobes closely approximated; eye relatively large; mesosoma box-shaped; fore- and hindfemora extremely widened and flattened distally; postpetiole broadly attached to gaster.

Biology
The presence of diaspidid scale insects inside all nests examined is a strong suggestion that they are a source of food for the ants. However, there are no direct observations of feeding or other interactions because ants stop normal activities and take cover as soon as the tunnels are opened. The five genera of diaspidids associated with four species of Rhopalomastix in Singapore all share the remarkable characteristic that females can reach sexual maturity without secreting a hard wax shield (Yong et al. 2019).

Nomenclature

 *  RHOPALOMASTIX [Myrmicinae: Melissotarsini]
 * Rhopalomastix Forel, 1900a: 24. Type-species: Rhopalomastix rothneyi, by monotypy.

Eguchi, Bui and Yamane (2011) - The worker of the single Vietnamese species has the following features. Worker monomorphic; head subrectangular; frontal carina and antennal scrobe absent; frontal lobes touching or separated only by a narrow longitudinal impression; median portion of clypeus weakly convex anteriorly, lacking median clypeal seta but bearing a pair of thick and short submedian setae; mandible small, with 4 teeth; antenna 10-segmented, with 2-segmented club; scape very short, extending a little beyond midlength of head when laid backwards; eye relatively large, located well in front of midlength of side of head; mesosoma box-shaped; promesonotal suture absent dorsally; metanotal groove absent; propodeum unarmed; metapleural gland bulla large; propodeal lobe absent; fore- and hindfemora extremely widened and flattened distally; petiole nodiform, with relatively high node, anteroventrally with well-developed subpetiolar process; postpetiole much shorter than high, broadly attached to anteriormost portion of gaster; gastral shoulder absent.