Added later. Some recent correspondence amoong my anty friends indicates this is probably a new species, but we'll leave it here till that is formalized.

Nice pictures! Nine-segmented antennae clinch the genus; pale color, the species.

The behavior is not at all unusual among ants that recognize one another. Possibly, these two flew from the same parent colony. It is also true, however, that queens that have flown will team up with others they encounter to establish a new colony. In some cases, only one survives after the workers appear, others continue to coexist in a multiple-queen colony.