Rhoptromyrmex

These uncommon ants have been found in leaf litter or foraging in loose columns on the ground, on logs and on low vegetation. They are known to feed on a range of smaller arthropods and to tend Hemiptera both above and below the ground. Nests are in soil or under bark on rotten logs and in surrounding soil, and can be very large. The queens of Rhoptromyrmex are unusually small when compared to workers. It is believed that they establish new nests by first invading the nests of other ants, or possibly established nests of their own species, and either replacing the original workers with their own, or, if in a nest of their species, recruiting a portion of the workers to leave the parent nest and begin a new nest with the new queen.



Worker of R. wroughtonii from Queensland.

Identification
The area of the clypeus immediately below the antennal sockets is raised into a sharp-edged ridge which forms the lower section of a pit around the base of the antennae. The front margin of the clypeus is strongly arched and projects forward over the rear section of the mandibles. The lower surface of the petiole is narrowed into a keel-like ridge. The propodeum near the insertion of the petiole has short, rounded flanges. The tip of the sting has a triangular to pennant-shaped extension projecting upwards from the shaft (visible only when the sting is extended).

The ridge-like structure of the clypeus immediately below the antennal sockets, as well as the projection on the tip of the sting, are unique to these ants and those in the genus Tetramorium. These two genera can be separated by the shape of the head (somewhat heart-shaped in Rhoptromyrmex, nearly square or rectangular in Tetramorium), the length of the clypeus (extending forward in Rhoptromyrmex, relatively short in Tetramorium), and the nature of the flanges near the insertion of the petiole (always rounded in Rhoptromyrmex, often spine-like in Tetramorium) as well as the lower surface of the petiole (keel-like in Rhoptromyrmex, rounded in Tetramorium).

Distribution and Habitats
Australian distribution

Regional Species Lists

 * Australia

Keys to Species

 * Australia