The idea that insects play has often aroused skepticism. Nevertheless, the authors investigated the occurrence of a playlike behavior in young individuals of a paper wasp. Polistes dominulus foundresses hibernate in aggregations and found associative nests in the spring. In aggregations, wasps exhibit most of the rank-dependent behaviors that they will use in the nest 6 months later. In aggregations, precocious dominance interactions are performed with exaggerated frequencies, whereas aggression and trophallaxis are rare. Dominance behavior in aggregations is apparently useless, but it probably allows wasps to assess their dominance potential without any apparent reproductive competition. Surprisingly, these interactions may be best interpreted as play because dominance behavior in aggregations shares several features with mammalian play fighting.