Why do fireflies flash?
At dusk, the trail to the lighthouse turns into a corridor of flashing light as fireflies emerge for their nightly mating ritual. The fireflies are so numerous that they illuminate the footpath on a moonless night. The flashing light is the firefly’s way of attracting a mate. For many species of firefly, the males emit a unique flash patterns to court females of the same species.
This is not unlike the characteristic flash pattern of beacons for aids to navigation on waterways. To help sailors tell beacons apart from one another at distance in the dark, each individual lighthouse or buoy is distinguished from those around it by the rhythm of its flashing and the color of light. For instance, the Saugerties Lighthouse has a white light that flashes off every 4 seconds.