Myrmelachista ramulorum
Diagnosis of worker among Antkey species. Antenna 9-segmented. Antennal club 3-segmented. Antennal scape length less than 1.5x head length. Antennal sockets and posterior clypeal margin separated by a distance less than the minimum width of antennal scape. Eyes medium to large (greater than 6 facets); break outline of head. Promesonotum separated from propodeum by metanotal groove, but never by a deep and broad concavity. Propodeum and petiolar node both lacking a pair of short teeth. Propodeum lacking posteriorly projecting protrusion. Waist 1-segmented. Petiole upright and not appearing flattened. Gaster armed with acidopore. Distinct constriction not visible between abdominal segments 3+4. Hairs not long thick and produced in pairs. Metapleuron with a distinct gland orifice. Color shining reddish brown.
Myrmelachista ramulorum is easily separated from other introduced and commonly intercepted ants by its antennae. It is the only Formicine species with a 9-segmented antenna and a 3-segmented antennal club. Brachymyrmex species have 9-segmented antennae, but they lack antennal clubs and also have flattened petiolar nodes (versus upright in M. ramulorum).