Question

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

Answer 1

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).    

Answer 2

Every firefly species has their own unique light pattern, so they can attract mates of the same species. The flashing is helpful when they need to find each other in the dark.  Female fireflies choose their mates depending upon specific male flash pattern characteristics.