Fireflies in vast swarms communicate with each other by producing bioluminescence to signal their presence and court mates. In particular, some species emit patterns of short flashes that have the potential to encode information. Male fireflies flash according to a species-specific pattern in order to attract and locate female partners. As multiple firefly species can share the same habitat, potential visual clutter could greatly hinder species discrimination and successful communication among conspecifics. We investigate how firefly flash sequences can co-evolve to be distinguishable by developing a method for simulating flash patterns that minimizes a cost function which incorporates similarity and predation risk. We observe an emergent periodicity in the resulting optimal sequences despite the lack of any constraints on the sequences to contain regular patterns. We also demonstrate a method of reconstructing potential cost functions from the phylogenetic relationships of extant species alongside their characteristic flash patterns.