A study on abdominal wagging in the fire ant, Solenopsis invicta, with speculation on its meaning

Social vertebrates have a rich repertoire of communication signals and modalities. Recent work on the social insects has uncovered a diverse set of communication modalities including chemical, tactile, visual, and auditory signals to communicate a wide variety of information on the location of distant food sites, distress, and aggression. Here, we investigated abdominal wagging in the fire ant, Solenopsis invicta. We found that the abdominal “wagging” that occurred inside the fire ant nests differed significantly from the abdominal “flagging” that is known to occur outside the fire ant nests. Neither sounds nor venom was emitted during abdominal wagging inside the fire ant nests. Moreover, the incidence and duration of abdominal wagging was greater when workers were tending brood or ingesting food than when engaged in non-brood related tasks or in donating food. Lastly, inside the nests, abdominal wagging neither attracted nor repelled nearby workers. Thus, we speculate that wagging is an expression of pleasure while tending brood or ingesting food that falls along the continuum between the aggressive nature of abdominal flagging and the distress call of abdominal stridulation.