Signal Recognition

Methods of Communication

While the light reaction serves as a defensive mechanism in firefly larvae, it is mainly utilized by adults as a means of species recognition and mating. Not all fireflies simply flash to grab the attention of potential mates, however; there are a variety of different methods by which fireflies can communicate with each other:

Both males and females produce photic signals, often with a specific frequency, length, and interpulse interval (IPI) (ex: Hotaria parvula).
The females, rather than the males, emit light - in this case, males fly around in the hopes of finding a sedentary, glowing female (ex: Microphotus).
The female is sedentary, and releases pheromones which are detected by males from longer distances. The female then glows so that the male can find her when he is within a closer range (ex: Pleotomus pallens).
Some species of fireflies do not produce light at all, and instead rely solely on pheromones for communication (ex: Lucidota atra).

In any case, almost all male fireflies emit a species-specific signal while flying, which is reciprocated by the signal of a sedentary female (Branham and Wenzel 2003).

Female Preferences

The male signal can provide a female with information about his location, species identity and spermatophore quality. A female firefly's preference for a particular flashing signal may be dependent on many different factors, such as "nutritional status, mating history, mate availability, temperature" and season (Michaelidis et al. 2006). In studies concerning the communication of Photinus greeni, females seemed to base their signal preference on male interpulse length (Figure 1). Generally speaking, many species of fireflies rely on a single aspect of the flash instead of multiple characteristics (Michaelidis et al. 2006).

Figure 1. Female response as a function of male interpulse interval in P. greeni. Females showed maximum response for an interval of 1 sec. (Adapted from Michaelidis et al. 2006.)