The significance of “abdominal signalling” in the obligate mutualism between Neochavesia caldasiae (Balachowsky, 1957) (Hemiptera: Xenococcidae) and Acropyga fuhrmanni (Forel, 1914) (Formicidae: Formicinae)

Abstract Mutualistic interactions between ants and hemipterans represent well-established examples of symbiosis. The interaction between ants of the genus Acropyga and the mealybugs they tend on roots is both permanent and obligatory. In this relationship, the honeydew produced by the mealybugs is exchanged for the protection provided by the ants, a process facilitated by several behaviors that promote cooperation between the species. We conducted systematic observations of interactions between workers of the ant Acropyga fuhrmanni and the hemipterans Neochavesia caldasiae that they tend across seven colonies in the laboratory. We reassessed the behavior previously termed “appeasement boxing” consisting of a rapid succession of movements of the mealybug abdominal apex which was erroneously attributed to the function of repelling the ant when the mealybug was disturbed during feeding. The behavior was recorded in multiple contexts and, in most cases, did not lead to the workers being repelled. Instead, this boxing behavior emerged within contexts of exploration, recognition, collection, and transportation of the mealybugs, frequently preceding their active manipulation by the ants. Our results indicate a multifunctional character, potentially associated with recognition, collection, and prioritization of transport. This finding warrants the revision of the expression “appeasement boxing” to “abdominal signalling” to more accurately reflect the function of this behavior within the close mutualism between Neochavesia caldasiae and Acropyga fuhrmanni .