Kenneth Setzer

Bioluminescence Comes in Many Forms

It seems as though it is that time of year again, when I become intrigued and enchanted by fungi. I always am, of course, but now in warmer weather I expect to find more fungi around — hopefully all outdoors. I’ve got it in my head to find bioluminescent mushrooms to photograph. I love mushrooms; but glow-in-the-dark mushrooms are like x100 on the cool fungi scale.

An Unassuming Click Beetle (Elateridae)

In the meantime however I am lucky to live where we have glowing beetles. Not fireflies (which are also beetles, not flies) but rather Pyrophorus noctilucus, an unassuming, even somewhat bland-looking wedge-shaped insect in the light, but turn out the lights and wait:

Pyrophorus Click Beetle

Not the best capture, but then again how can you really show something like this anyway? It has to be dark to appreciate the glow, but if it’s really dark, your camera will have a hard time focusing on two little glowing green spots.

Unlike fireflies, Pyrophorus beetles do not blink, but emit a steady light from two light-producing organs on their pronotum (area behind the head), which only slowly fades. They can even change the brightness of their light; if you touch one, they will assume you are a  predator and glow very intensely, like a pair of LEDs. It turns out many creatures create light through chemical processes like this. Fish, fungi, insects, bacteria all have species that use bioluminescence for communication.

I always look forward to the first Pyrophorus beetles of the year, which have always appeared in May (to coincide with my birthday, I choose to believe). Now this year, my wife spotted the first visitor, at least ten days ago in mid-April, the earliest I have ever seen them here in South Florida.

If glowing intensely weren’t enough, these guys do even more. They glow, they fly, they click! They do it all. Hold one in your hand, and if upside down, it is able to click using its body segments, the force of which will launch the beetle a few inches into the air, thus righting itself and startling a would-be predator.

Beetle Headlights

Pyrophorus beetles don’t stay for long. They need to mate and lay eggs (which are said to also glow) to ensure they re-appear next year. They are a welcome gift for me every spring.

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