Flash! I saw the first firefly of the young summer strutting his stuff tonight, lighting my way while walking the dog. And I do mean he: the fireflies you see flying and flashing are males, advertising their wares by sending signals into the night.
The larger females are flightless, sitting in grasses or on branches checking out the light show above them.
And each species of firefly has its own unique Morse code, using both time and space to alert others as to which species it might be. So one firefly performa a flashing J pattern, distinct from the one that performs, say, one low dash, or three high dots.
When the female spots an acceptably sexy flashing male of the proper species, she has the appropriate answer, a coded response. He flies to the signal, and mating ensues—and she soon lays eggs that themselves even glow in the dark!
But it gets even better: in one group of fireflies, the female has decoded the flashing pattern of males of different species. He flashes, looking for a mate; she responds. He flies down, visions of sugarplums dancing in his head… And she devours him.
Sex and food explain just about everything in nature, even the welcome flash of fireflies.