Firefly synchrony: a behavioral strategy to minimize visual clutter.

Most firefly species (Coleoptera: Lampyridae) use bioluminescent flashes for signaling. In some species, the flashing between males occurs rhythmically and repeatedly (synchronically) with millisecond precision. We studied synchrony's behavioral role in the North American firefly, Photinus carolinus. We placed a female in a virtual environment containing artificial males that flashed at varying degrees of synchrony. Females responded to an average of 82% of synchronous flashes compared with as few as 3% of asynchronous flashes. We conclude that one function of flash synchrony is to facilitate a female's ability to recognize her conspecific male's flashing by eliminating potential visual clutter from other flashing males.