A couple of years ago, wildlife photographer Jeff Cremer stumbled upon something very special during a night hike in the rainforest of Tambopata, Peru. While passing a bend on the trail, he noticed several glowing green dots embedded within a dirt wall. Curious and seeking more information, Jeff snapped some pictures and posted them to Reddit in a section where site users help to answer questions and identify species. It turns out, these glowing dots were likely due to some kind of insect larvae, possibly a beetle, but the rest of the story remained a mystery. What exactly was this strange species and why were they glowing in the middle the Amazon rainforest in a dirt wall? This past October, Jeff was accompanied by entomologist Aaron Pomerantz and his colleagues Mike Bentley and Geoff Gallice, who are graduate students at the University of Florida. Together, they hoped to “shed some light” on this glowing mystery.
Several green glowing dots can be seen on this dirt wall in the Amazon rainforest.
Animals that produce and emit their own light have been of great interest to biologists, chemists, and pretty much any nature lover who has had the privilege of encountering one of the many glowing critters out there. There is something mesmerizing and beautiful about an ocean lit up by glowing plankton or watching an open field come alive at night, illuminated with fireflies. The technical term for this glowing phenomenon is known as bioluminescence, and it has evolved many times in the animal kingdom. There are several different reasons that animals utilize this emission of light including: attracting mates, defense against predators, and luring in prey. And this last reason brings us back to our mysterious glow worms…
The larvae up-close, showing off the luminescence from the glands near the head.
As Aaron points out in the video, these larvae are sticking their glowing heads out of the dirt wall with their freakish looking mandibles outstretched. This immediately tipped off the entomologists that this appeared to be a sit-and-wait, or ambush, predatory strategy. You’ve also probably noticed that some insects seem to flock to your porch light at night; the glow worms may be taking advantage of this attraction to light phenomenon. That is, they may emit a green light and wait for a nice juicy insect to come right into that lure, and right into those powerful mandibles. This is not unlike the strategy that deep sea angler fish employ to lure prey. The light production in these glow worms is likely due to a molecule known as Luciferin, which is also the compound that many firefly species use to emit light.
Zoomed in on the mouth parts.
Mike helped confirm our predator hypothesis by presenting the larvae with a stick and then an ant. Sure enough they were voracious, clamping their mandibles shut and dragging their prey into the tunnels...never to be seen again. Due to their predatory nature coupled with the fact that these monstrous looking glow worms reminded us of the movie Tremors (a 1990 western film about killer underground creatures), we just had to take several close-up pictures for your viewing pleasure.
The glowing larvae with its freakish mandibles outstretched and waiting for the next unsuspecting victim.
So what species did we investigate here? We believe these belong to a family of beetles called Elateridae, which are commonly known as click beetles. But beyond that, we are not entirely sure what species this is or if it has been described yet (perhaps through the power of the internet we can get an answer). Elateridae is a very large family with around 10,000 described species in the world and only about 200 species have been documented to display bioluminescence. Some species of glowing beetle larvae in Brazil can be found in old termite nests where they attract and catch prey like ants and termites. The behavior that we observed where the larvae had utilized a dirt wall, as opposed to a termite mound, for their home and hunting ground could be a different niche not yet documented for this enigmatic group of glow worms.
Close-up of the glow worm head. Cute, huh?
So at the end of the day, why should we care about these critters? Aside from the fact that they are downright bizarre and extraordinarily cool looking, the science behind bioluminescent click beetles is still lacking. What role do they play in the complex environment and ecosystem of the Amazon rainforest? Why exactly did they develop the ability to produce their own light, and how did this trait evolve? What can they teach us about their biochemistry and the biodiversity of life on our planet? These questions are far from answered, but perhaps a curious naturalist will come along and help to solve this, and many other, Amazonian mysteries.
An infographic on our predatory glow worms. Click image to enlarge.
We hope that this story has sparked a little fascination in you, because it certainly did for us when we first laid eyes on them! We will investigate these amazing glow worms further to see what more we can learn while seeking to protect them and their environment.
-Aaron Pomerantz, Entomologist
You can follow Aaron on Twitter @AaronPomerantz
Visit Refugio Amazonas and see these glow worms!