Phylogenetic studies suggest that historically all paper wasps (Vespidae: Polistinae) in North America have tropical origins, but some species have adapted to survive temperate conditions. Subtropical climates, which are intermediate between temperate and tropical, allow a unique opportunity to study ancestral traits which can be retained or lost within populations, and ultimately elucidate the process of social wasp evolution. We investigated the phenology of paper wasps at study sites in subtropical Baton Rouge, USA, through nest searching and monitoring of nest parameters throughout the warm season (March-October). Across the year, two periods of nest initiation occurred: from March-May (early season nests, i.e., before the summer solstice), and from July-September (late season nests, after the solstice). We observed 240 Polistes nests from six species, of which 50.8% were initiated in early season and 49.2% in late season. In contrast, Mischocyttarus mexicanus rarely built late season nests and had longer early season colony duration than Polistes bellicosus and P. dorsalis, which built more nests in the late season than early. Across all species, late season nests had significantly shorter colony duration (~87.6 days) than early season nests (~166 days), and only P. bellicosus had fewer adults at peak population in late season nests than in early season nests. Results indicate both a bivoltine colony cycle in Polistes of subtropical climates, as well as differences in nesting strategies between genera.
Keywords: Mischocyttarus; Polistes; eusociality; phenology; voltinism.