D: On summer nights, the lights of fireflies are beautiful, and their flashes help them attract mates. I wonder though, wouldn’t those same flashes of light also help predators home in on a tasty snack?

Y: Some animals are carefully camouflaged and predators can’t see them. But you’re right, Don, others stand out prominently. Fireflies are one example of a prominent animal, monarch butterflies are another.

D: But Yaël, monarch butterflies taste awful and are poisonous. Their bright orange color works to warn birds and other predators away from a very unpleasant experience. Are fireflies poisonous too?

Y: You guessed it. They are. Predators show intense aversion to them. Some die within hours of eating fireflies. In a 2018 study, American researchers reported that bats showed intense aversion to the beetles, always spitting them out, coughing, and shaking their heads.

D: Bats? Why bats?

Y: Bats are one of the most important predators of night active insects.

D: But Yaël, everybody knows that bats use sonar echolocation to find insect prey in the darkness of the night. Could firefly light flashes really warn them away, like the monarch’s colors do for birds?

Y: Bats can also see. Researchers did an experiment to test the role that vision and echolocation play in bats’ detection of fireflies. They exposed bats to two groups of fireflies. One group was normal. In the other, fireflies were darkened by having their bioluminescent organs covered over with paint. The bats could learn to avoid either group of fireflies, but they learned faster with normal than with darkened fireflies. Vision and echolocation work together to help bats avoid the unpleasant mistake of eating a firefly.