The Cannibal Firefly

Every summer night, I stay up late to catch fireflies. Then, one night, I saw a glow color different from the others. So I decided to catch  the firefly that emitted the strange light because I thought it was rare. I successfully caught the firefly. When I caught a jarful of the insects, I put them in a terrarium and started to brush my teeth. 

One firefly that I caught was stronger than the others. At that time, I did not know that fireflies could eat other fireflies. So I put it in with the others. When I got out, I saw that the big firefly was EATING ITS OWN KIND!

Do you think fireflies are harmless? Think again!

There are many species of fireflies, grouped into genera. The large firefly is Photuris and the small firefly is Photinus.

Note the difference in the elytra: While the Photuris firefly has three yellow stripes. But the Photinus firefly has no stripes. The Photuris is also stronger and has a different thorax color. It also even has an arrow pattern on its thorax while the photinus has just a spot. It even has a different light color: it flashes neon green, instead of yellow.

Another huge difference between the Photuris and Photinus fireflies is Lucibufagin production.

Lucibufagin is a toxic steroid that is poisonous to animals. When squeezed or pinned, a firefly sweats and sometimes bleeds lucibufagin compounds all over itself! It does this to deter its predators, like ants, spiders, and even bats and birds. The animals do not eat fireflies because lucibufagin is poison! It is also distasteful. Lucibufagin toxins can cause heart failure and breathing problems. Even in humans!

The smaller firefly (Photinus) can produce it to defend itself from predators. But the large firefly (Photuris) does not make Lucibufagin. To protect themselves and their eggs from predators, the large Photuris females learned to mimic flashes of the Photinus females to attract the smaller fireflies that are rich with lucibufagin. And then they eat them! The bodies of the large fireflies have much less lucibufagin, but they are still very poisonous.

Fatal facts:

• Some Photuris fireflies gather in packs of 2 or 3 to hunt down more Photinus fireflies.
• American lizards do not eat fireflies because they learned that they are poisonous (through evolution).
• But pet Bearded Dragon lizards (Pogona vitticeps) eat fireflies. That is because they are native reptiles to Australia, where there are no fireflies at all. So they don’t know that lucibufagin is poisonous.
• If a Bearded Dragon eats a single Photinus firefly, it will die.

References:

Presentation I made about it at school.

My iNaturalist page about the fireflies observed above.

The entomologist from Cornell University who helped me with this research.

Great book by Thomas Eisner with a chapter on cannibal fireflies.