The timing of conflict and cooperation among cofoundresses of the social wasp Polistes fuscatus (Hymenoptera: Vespidae)

Field observations were made on 37 preworker, multiple-foundress colonies of the social wasp Polistes fuscatus. In total, 401.9 h of behavioural observations of cofoundresses were conducted at three different periods prior to the emergence of workers. Cofoundresses displayed a marked, significant increase in aggression at about the time in the colony cycle when reproductive-destined eggs began to be laid. Both queens and their subordinates became increasingly aggressive at this time. These empirical results support theoretical predictions that conflict among cofoundresses would intensify over the production of reproductive-destined (but not worker-destined) eggs. Cooperation in foraging to minimize nest inattendance as well as synchronicity (temporal overlap) in activity also increased significantly at the onset of the production of reproductive-destined eggs. Thus, conflict and cooperation are not necessarily antagonistic in P. fuscatus. Foundresses minimized the time that nests are unattended at a time in the colony cycle when most conspecific usurpations occur. This suggests that the ecological pressure of conspecific usurpation has favoured increased coordination in foraging to minimize the time nests are unattended. The adaptive significance, if any, of an increase in synchronicity of activity among cofoundresses at the onset of the production of reproductives is not obvious.