One of the many remarkable traits that periodical cicadas exhibit is that all individuals at any location are completely synchronized to emerge on a single year. Emergence is synchronized over large areas but several ‘broods’ (synchronized populations that emerge on unique years) are known to exist. Many workers have observed that very little overlap exists in the geographical distribution of broods. In this study, we used a mathematical model to explore the mechanisms behind the allopatric distribution of broods. This model incorporated both intraspecific competition of cicada nymphs with inversely density dependent predation by birds on cicada adults in a coupled map lattice framework. The model demonstrated that predation generates an “Allee effect” that functions to exclude rare broods. The model was tested by sampling the presence/absence of cicada populations at the border between broods V and VIII in southwestern Pennsylvania. Results generally confirmed the predictions of the model though in some areas broods overlapped and in other areas, neither brood exists.