• Bioluminescence;
  • fireflies;
  • insects;
  • landing;
  • mating behavior;
  • synchrony

Abstract The flash communication system of Photinus carolinus in Great Smoky Mountain National Park (Tennessee) is characterized by male firefly synchrony. Photinus carolinus males signal a conspecific female with synchronic trains of flashes. A solitary responding female attracts several males, which is not common in North American rover fireflies. The female and the group of males that she attracts are called a cluster. It is hypothesized that the first male attracted to the female would land closer to the female than would additional males because there would be less tendency for visual confusion. This hypothesis is explored under controlled conditions by replacing the responsive female with an appropriately flashing light-emitting diode (LED) located in the center of a flat target area. When infra-red videography is used to measure the first male and the additional males’ landing distances from the counterfeit female (LED), most fireflies land within 15 cm of the target LED, and the first male does not land closer than the additional males. It is suggested that cluster formation is a by-product of male synchrony and is facilitated by the tendency of males to land near, but not on, females.