Recently I’ve learned via Twitter that lots of cats (dogs, too) enjoy chasing after fireflies. But please don’t let your pets eat the fireflies! This is for their own sake, not for the fireflies.
Living in a world full of insect-eating predators, fireflies have evolved potent defenses to protect themselves. Firefly blood carries a bitter-tasting and toxic chemical called lucibufagin (lucifer = Latin for light bearer + Bufo = toads that produce similar chemicals).
Lucibufagin (often nicknamed LBG) makes a powerful poison because it is effective against almost any animal. It binds to and disables an enzyme, known as the sodium-potassium pump, that’s essential for all animal cells. This enzyme actively transports ions across cell membranes, generating an electrical potential that allows us to do really important things like think and move our muscles. To protect themselves, many plants and a few animals have converged on stocking similar toxins in their chemical arsenal.
Not only are fireflies toxic, but they also smell bad and taste terrible. Because of this, many creatures consider fireflies repugnant, including lots that normally make their living by eating insects – birds, monkeys, toads, lizards, geckos, and chickens all disdain fireflies.
But certain lizards have died after eating just a few fireflies, a phenomenon known as firefly toxicosis. Yup. Some well-intentioned owners fed fireflies to their pet Pogona bearded dragons, lizards native to Australia. The bearded dragons ate the fireflies, then began violently shaking their heads and repeatedly gaping their mouths. Their bodies, normally tan, turned black. Within hours, they keeled over and died.* According to the ASPCA, ingesting merely half a firefly will kill a full-grown bearded dragon.
So sure, go ahead and let your cats admire the fireflies as much as they want. But please don’t let your pets eat them!
Read more about fireflies’ defensive arsenal in Silent Sparks – Chapter 7: Poisonous Attractions.
And here you can watch a Tallahassee tree frog get lit by swallowing a firefly.