ABSTRACT I give an account of the first known example of an ant (i.e., an undescribed Dorymyrmex ) that licks and nips the much larger workers of a different ant species ( Pogonomyrmex barbatus ) in a manner remarkably parallel to the actions of cleaner fish that clean other species of fish. Specifically, the potentially aggressive individuals being tended encourage these attentions by stationing themselves in a distinctive, rigid posture at particular locations (in the case of the ant, near the nest of the cleaner species) and even permit a cleaner to inspect between their open mandibles. The payoffs of this activity for both the cleaners and the tended workers have yet to be worked out.
Mark W. Moffett (Wed,) studied this question.