Predatory Fireflies

Femme fatale firefly preying on a smaller male from another species
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Predatory fireflies (genus Photuris) are a group of fireflies that can mimic the light signals of females from other species. They are also drawn to the flashier males of other species.

Cannibal Cousins

How did such an ability evolve? It isn’t to difficult to imagine food selection and competition being a major catalyst for the evolution of this relationship. As food was scare, those fireflies with the ability to detect and feed on other species survived more than those that did not. In fact, all fireflies are born predatory. They later feed primarily on pollen and nectar as adults except for the predatory species known as the femme fatales. Much like many species that may have retained their immature forms, humans included, the fireflies that maintained their predatory instincts even into adulthood probably provided an evolutionary advantage in one population as opposed to another. In other words, if you eat well, you can probably make more babies.

Photuris lucicrescens on a leaf. Back facing us.

Photuris lucicrescens, cousin cannibal – Image Source: Wikipedia

 

It’s A Trap!

The Photuris females lure in males by way of mimicry. Once Photuris lands nearby she responds with a flash of her own, the unsuspecting male interprets her response as one coming from his own species. He investigates and faces an inevitable death. Photuris has other talents. The females can also identify the flashes of particular male species as well. Then, like a moth to a flame, Photuris seeks out the most attractive of the lighting patterns. This makes sense as the males are trying to attract a female (just as peacock males flaunt their plumage to attract a peahen). However, in the case of Photinus carolina, Photuris’s favorite prey, being too flashy can be deadly. So, male fireflies signal moderately and they also flash synchronously which provides some confusion for predators. Just like in schools of fish, you have more protection in greater numbers; and hopefully, you don’t stand out too much.

Photinus carolinus lighting up alone on a leaf

A beautiful Photinus species: Image Source: https://tourdefarm.in

Other Defenses

When in danger, the males may drop to the ground, scurry or fly away. They also have a distasteful chemical in their bodies which ward-away predators. Unfortunately, that individual will still die, but having this trait benefits the entire species by teaching predators to not eat that species. This doesn’t really help against predatory fireflies; but overall, it still reduces predation rates and the species continues on.

Femme Fatale eating a smaller male

Femme Fatale eating a smaller male, Thomas Eisner from Cornell University.

 

Video Resource: Dr. Rebecca Nichols talks fireflies.

Critical Thinking:

  • How might light signalizing have evolved?

 

Bio Fact: The protein that produces the glowing is an enzyme called Luciferase. Luciferase has been placed in a number of plant species such as Tobacco. Yep, it glows.

Fluorescent Tobacco

Fluorescent Tobacco: Image Source: Genetics and Genomics Wiki

 

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