People often ask me this excellent question. Yet it doesn’t have a quick or easy answer. One reason is that different species live in different habitats. For instance, the salt marsh firefly Micronaspis floridana is restricted to intertidal regions along the Florida coast. Another reason is that certain things matter to adult fireflies, whereas different things matter to the juveniles.

Some species have specialized habitat requirements (photo by Drew Fulton)
For adult fireflies, what’s most important is finding a dark place for their courtship displays. Artificial lights – streetlamps, outdoor security lights, even car headlights – can disrupt firefly courtship conversations. Such bright backgrounds make it difficult for fireflies to see each other’s courtship signals. Another desirable habitat feature for adult females is easy access to suitable egg-laying sites, like moss, moist soil, or decaying wood.