A New Type of Synchronized Flashing in a North American Firefly

Abstract

Continuous synchronic flashing occurs in stationary and flying male congregations of members of some firefly species in Southeast Asia. In the present paper, low-light videography and photometry was used to demonstrate that synchrony occurs in the North American genus Photuris. We found that the Georgia coastal plain firefly Ph. frontalis flashed synchronically. From a distance, the synchronic flashes of a population of flying Ph. frontalis appeared to occur in a continuous synchrony. However, when pairs of males were viewed, it was difficult to verify that their flashing was continuously synchronic. In the laboratory, caged fireflies flashed synchronically, stopped, and then flashed synchronically again. To study this flash behavior, recordings of individual and group flashing were analyzed statistically to validate the conclusions about rhythm and synchrony. Although the mass synchrony appeared continuous, the individual flying males switch on and off, coming in again on the beat. The synchrony in Ph. frontalis is common and pervasive rather than rare and sporadic, as shown by other North American fireflies. The precision of the frontalis synchrony approaches that of Southeast Asian fireflies. The intermittent synchrony of this firefly reinforces the evidence that there is a diversity of synchronies in fireflies.