Mechanism of rhythmic synchronous flashing of fireflies. Fireflies of Southeast Asia may use anticipatory time-measuring in synchronizing their flashing.

In Thailand, male Pteroptyx malaccae fireflies, congregated in trees, flash in rhythmic synchrony with a period of about 560 +/- 6 msec (at 28 degrees C). Photometric and cinematographic records indicate that the range of flash coincidence is of the order of +/- 20 msec. This interval is considerably shorter than the minimum eye-lantern response latency and suggests that the Pteroptyx synchrony is regulated by central nervous feedback from preceding activity cycles, as in the human "sense of rhythm," rather than by direct contemporaneous response to the flashes of other individuals. Observations on the development of synchrony among Thai fireflies indoors, the results of experiments on phase-shifting in the American Photinus pyralis and comparisons with synchronization between crickets and between human beings are compatible with the suggestion.