Behavioral Consequences of Sensory System Constraints in the Firefly Photinus carolinus

Abstract

Fireflies use bioluminescent flashes to establish a dialogue between conspecific males and females. Through this dialogue, receptive females attract conspecific males for mating. In most firefly species, the males act as independent agents. That is, as they fly and flash in search of a responding female they do not appear to coordinate their activities with other males. In marked contrast, the males of some firefly species coordinate their flashes to coincide with those of other conspecific flashing males, resulting in synchronous flashing across local populations. We propose that the need for synchrony in these species may be driven by constraints imposed by the female visual system. Since males are flying while flashing and may appear to flash from different spatial locations, the female must attend to flashes over a wide visual field. But doing so has a drawback. She may see the flashes of multiple males within her wide visual field and their flashes could interfere with her ability to respond to any single male. We present evidence of a sensitive period during which extraneous flashes interfere with a female’s response to a conspecific male and develop a model to predict how the number of independently flashing conspecific males affects the female’s responsiveness. By coordinating their flashing, the males reduce the chance that any of them will flash during the female’s sensitive period. This minimizes interference with establishing the male–female dialogue that would otherwise result by the presence of many patrolling males being in the female visual field. We conclude that the constraints imposed by the female visual system could be a factor driving the need for males to synchronize their flashing if they tend to fly and flash at high population density.