One of the first chat sites online was called firefly, and for good reason. On summer evenings, fireflies create a chat room of light flashes to communicate information about their species, virility, and willingness to engage in a romantic liaison. Each species has a signature flash color and pattern used at a specific time in the evening. Male fireflies initiate communications by flying and flashing in a particular pattern. One of the most common fireflies in the United States, the big dipper firefly (Photinus pyralis), flies in a J-shaped curve as it flashes. Females watch the display, and flash back if they are interested in hooking up. The night shimmers with booty calls.
Like in human online dating, it is possible for fireflies to misrepresent themselves. Female Photuris versicolor fireflies lure in unsuspecting males of other species by responding to their signals with the flash pattern of a female of the male’s species. When a male firefly arrives expecting a good time, he is devoured by the P. versicolor female. Female Photuris can receive more from this encounter than just a tasty snack. Female Photuris fireflies cannot produce lucibufagins, which are defensive compounds that are distasteful to predators like spiders. However, when they eat a male Photinus firefly they can acquire these compounds and use them in their own defense.
Sexy-times aren’t the only thing that fireflies communicate using their bioluminescence. Larvae still bioluminesce, which is thought to be a signal to predators that the insects are unpalatable and toxic. This is similar to brightly colored animals that use their colors as a warning to predators. In both the cases of bioluminescence or bright warning colors, mimics abound. Some mimics are also toxic, and use a shared warning signal to reinforce the idea that predators should stay away. On the other hand, some mimics are tasty, but take advantage of the same signals to hoodwink predators.
Abundant firefly mimics exist across a wide range of taxa. Glowworm beetle larvae are unpalatable, and demonstrate this using bioluminescence. Some millipedes and centipedes also use bioluminescence as a warning. Bioluminescent earthworms are not chemically defended, but likely use light flashes to scare off underground predators.
Cratoplastis moths don’t advertise their toxicity using bioluminescence, but their coloring closely mimics that of fireflies. Some flannel moths also mimic the coloring of fireflies, but they tend to be toxic only as caterpillars. Flannel moth caterpillars are incredible from a chemical ecology point of view. Do yourself a favor and read this article from WIRED: Never touch anything that looks like Donald Trump’s hair.
Fun fact: Like the deep-sea anglerfish, some fungus gnat larvae use bioluminescence to lure in prey. Prey are attracted to the light source, and get caught in a trap of sticky threads.
Featured image by Wikipedia user Quit007.
Eisner, T., M. A. Goetz, D. E. Hill, S. R. Smedley, and J. Meinwald. 1997. Firefly “femmes fatales” acquire defensive steroids (lucibufagins) from their firefly prey. Proceedings of the National Academy of Sciences of the United States of America. 94 (18): 9723–9728.
Lloyd, J. E. 1975. Aggressive mimicry in Photuris fireflies: signal repertoires by femmes fatales. Science, 187 (4175): 452-453.
Oba, Y., M.A. Branham, and T. Fukatsu. 2011. The terrestrial bioluminescent animals of Japan. Zoological science, 28 (11): 771-789. (http://www.bioone.org/doi/pdf/10.2108/zsj.28.771)
In a flash: firefly communication by Science Friday