Fireflies put on the most gruesome, beautiful show of the summer
To the outside observer, the dancing lights of fireflies at night may seem like a whimsical, romantic spectacle. Fireflies participating in this woodland dance probably wouldn’t agree with that take on things. For a species like Photinus carolinus, the blinking is the final phase of their life, when they have two to four weeks to find a mate. The stakes are raised a bit further thanks to some predatory impostors devouring the eligible bachelors.
The mating display starts off pleasantly enough. Male P. carolinus fireflies assemble in the woods on warm summer nights and begin to coordinate their show. Groups of males will blink six times, then pause, then again until they’ve managed to sync up with each other. Eventually the flashing illuminates the forest like like a giant, silent, night club, blinking until midnight in good weather.
This singles’ scene does attract trouble though. Many predators understand the bright coloration of the fireflies to be a warning against eating them, as compounds in their bodies are slightly toxic and carry a bad taste, similar to a monarch butterfly’s bright orange warnings to birds. This doesn’t act as a warning to predatory fireflies, however, and members of the genus Photuris instead see this display as a big invitation to get some easy dinner plus stock up on said toxins for their own body’s defenses.
Bleeding to live
Photuris fireflies are capable of imitating the blinking patterns of other species, which they use to trick P. carolinus males. Blinking like a receptive female, the Photuris firefly lures the P. carolinus close enough that they can be captured and eaten. The last line of defense for the duped male is “reflex bleeding,” wherein he secrets blood, loaded with what should be distasteful toxins, out of pores in his exoskeleton, theoretically reminding the predator that he is not the best choice for a meal. Against the otherwise immune Photuris firefly, however, the blood is only useful because it’s also sticky, and might possibly immobilize the predator long enough for the P. carolinus male to escape.
Photuris fireflies don’t give up too easily though. They’ve even been observed retrieving P. carolinus fireflies from spiderwebs, battling the arachnids for the meal if necessary. They sometimes lose those challenges and become a meal themselves, adding further to the death and carnage of the beautiful show we enjoy each summer.
Source: Fireflies Are “Cannibals”—And More Surprising Facts About the Summertime Insect by Jason Bittel, Weird and Wild