What visual signal do male fireflies use to attract females?

Male fireflies use bioluminescent flashes to attract females.

The light is produced in specialized abdominal organs through a chemical reaction involving luciferin, luciferase, oxygen, and cellular energy. In many species, males fly or perch while displaying a species-specific pattern of flashes. Females respond with a timed flash of their own, allowing the two sexes to recognize one another in darkness.

Flash timing is crucial: the pattern, interval, duration, and height of the display can help distinguish one species from another. Firefly communication is therefore more than simply turning a light on and off. It is a visual courtship code shaped by evolution.

Not every firefly uses the same strategy. Some females of the genus Photuris attract males of other species and consume them, acquiring defensive chemicals from their prey. Fireflies are beetles, not flies, and their light is generally considered highly efficient because little energy is lost as heat.