These femmes fatales reveal the dark side of fireflies

© Kevin Collins/KQED Science

Trickster vixens from the genus Photuris lure males of other firefly groups to their gruesome demise.

Fireflies are magical. They are romantic; nature’s built-in fairy lights that fill a summer’s evening with twinkle and whimsy – they are the creatures of childhood and fairytales. Who doesn’t love fireflies?

But alas … Mother Nature doesn’t always conform to storybook revelries, and in the case of some fireflies, things get downright gory.

Meet the ladies of the firefly genus Photuris.

When many fireflies mate, males bestow the females with a gift of extra lucibufagins, a chemical cocktail that wards off predators like spiders and birds and aids the reproductive success of the parents.

Unfortunately for Photuris fireflies, they lost the ability to make their own lucibufagins. So instead of chemistry, writes Elliott Kennerson for KQED Science, “these bigger, stronger fireflies became adept at imitation, and evolved to turn into insect vampires to take these valuable compounds from other fireflies to boost their own defenses.”

They do this by mimicking the specific flash patterns of other firefly species – when an unsuspecting suitor approaches, well, she eats him! Like, just completely devours him. Of course, it’s not her fault … she’s just doing whatever it takes to survive. And as it turns out, the male has some pretty fancy defense moves in return.

Watch it all in fascinating (and just a bit frightful) detail in the Deep Look video below. And don’t let it darken your soft spot for fireflies. You can’t really have a satisfying fairytale without a little conflict.

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