Independent- and swarm-founding wasps represent two discrete social syndromes, differing from each other in a number of traits that include colony size, level of social complexity, queen number, division of labor among workers, nest architecture, body size, and ecological dominance. Swarm founding evolved independently at least four times in the Vespidae. While much attention in recent decades has been paid to unraveling the steps leading to eusociality in the vespids, virtually none has been devoted to understanding how swarm founding evolved from its ancestral independent-founding state. Here I suggest possible scenarios by which the transition could have occurred. I argue that the key initial step was the evolution of pheromonal queen signaling, which enabled the evolution of larger colonies. Larger colonies in turn led to the decentralization of colony control away from a dominant queen and onto the workers. Other traits of the swarm founders, including polygyny, nest envelopes, nocturnality (in Apoica and Provespa), and small body size, probably evolved later. Swarm founding appears to be an inevitable outcome of the evolution of larger colony size among tropical vespids.