Abstract: Abstract We show that in French Guiana the large carton nests of Azteca chartifex, a territorially-dominant arboreal dolichoderine ant, are protected from bird attacks when this ant lives in association with Polybia rejecta, an epiponine social wasp. Because A. chartifex colonies are well known for their ability to divert army ant raids from the base of their host tree so that they protect their associated wasps from these raids, there is a reciprocal benefit for these two partners, permitting us to call this association a mutualism. We also show that P. rejecta nests are significantly less often attacked by birds than are those of two compared epiponine social wasp species. Furthermore, experimentation using a standardized protocol demonstrated the significantly higher aggressiveness of P. rejecta compared to seven other wasp species. We conclude that the efficacious protection of its associated ant nests is likely due to the extreme aggressiveness of P. rejecta. © 2015 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.