Is the firefly flash regulated by calcium?

The very different courtship flashes of Photuris versicolor and Photuris lucicrescens males mirror the pattern of neural impulses produced by their brain. Their lanterns luminescence very differently, however, in response to direct, electrical stimulation. Whereas P. lucicrescens lanterns glow in response to high frequency, continuous electrical stimulation, those of P. versicolor produce only rapid, triple-pulsed flashlettes that resemble, but are not identical to, their courtship flashes. In addition, the exposed lantern tissue of P. versicolor males, when immersed in firefly saline high in potassium and calcium ions, scintillates with hundreds of photocytes flashing in random fashion. P. lucicrescens male lanterns, so treated, only glow. Tests of P. versicolor lanterns with salines of different composition suggest that calcium ions are essential in producing this intense, long lasting scintillation response and are therefore possibly implicated in the final stages of flash control in this species.