Why might it be beneficial for each firefly species to have its own unique light pattern?

Fireflies use the bioluminescence to attract mates for mating hence key in reproduction. Therefore, beetles from different species should have different lighting patterns so that they can only attract mates of the same species. This would avoid interspecies mating which would probably involved expending energy in produce nonviable offspring which is inefficient (hence will be unfavoured natural selection).    

Iwould say silver and gold