Panama has a reputation for spectacular wildlife. Visitors come looking for monkeys swinging through the canopy, sloths hanging motionless from trees, toucans calling from the forest and frogs appearing like living jewels after a rainstorm. But some of the country's most fascinating creatures are so small that they can easily be missed.
Then the sun goes down.
As the jungle becomes dark, tiny points of green, yellow and sometimes yellowish-green light can begin appearing among the leaves. Some blink. Others glow continuously. Some fly through the forest like miniature lanterns. Others remain almost completely hidden in the vegetation.
These are Panama's bioluminescent insects, and they turn a nighttime walk through the rainforest into something that can feel almost supernatural.
Fireflies: The Familiar Lights of the Tropics
The most famous glowing insects are fireflies, which are actually beetles, not flies. They belong to the family Lampyridae, a remarkably diverse group containing roughly 2,000 described species worldwide. Many firefly species use their lights as signals, particularly during courtship.
In Panama's tropical environment, fireflies can be encountered around forests, fields, gardens, streams and other areas where suitable habitat remains.
The magic happens when darkness arrives.
A single flash might appear in the vegetation, followed by another several metres away. Then another. Suddenly the darkness seems to contain dozens of tiny stars.
Unlike an artificial light, the glow of a firefly produces remarkably little heat. The insect creates light through a chemical reaction involving luciferin and luciferase inside specialized light-producing organs.
And there is an important reason for those flashes.
For many fireflies, the nighttime display is essentially a conversation. A male produces a particular flashing pattern, and a female of the same species may respond with her own signal. What looks like random flickering to a human observer can therefore be a highly organized mating system.
The rainforest floor can effectively become a gigantic dating network.
Panama Has Something Even Stranger: Glowing Click Beetles
Fireflies aren't the only insects capable of producing light.
Panama is also home to bioluminescent click beetles, including members of the genus Pyrophorus. These are among the most extraordinary insects a person can encounter on a night walk.
Unlike the rapid flashing associated with many fireflies, these beetles can produce a much more continuous glow. They possess specialized light organs on their bodies, including two conspicuous organs toward the rear corners of the thorax. Some also have a larger light-producing organ on the underside of the abdomen.
Imagine walking down a jungle trail and suddenly seeing what appear to be two tiny green headlights moving toward you.
That is the sort of encounter that can happen with a glowing click beetle.
There is even photographic documentation of a Pyrophorus click beetle found at night in El Valle de Antón, Coclé Province, demonstrating that these spectacular insects occur in Panama's humid forests.
The Panamanian Fire Beetle That Helped Scientists Understand Light
One particularly fascinating species is the Panamanian luminous click beetle Pyrophorus angustus.
Scientists have actually studied its luciferase — the enzyme involved in producing its light — at the molecular level. Research found that the beetle has different luciferase systems associated with its dorsal and ventral light organs, producing different wavelengths of light.
In other words, the glowing insect wandering across a Panamanian leaf isn't simply carrying a little biological flashlight.
Its body contains a sophisticated biochemical lighting system.
And scientists have been able to use these organisms to understand some of the fundamental mechanisms behind bioluminescence.
Why Do They Glow?
The obvious question is: Why would an insect evolve the ability to produce light?
There isn't one universal answer.
In fireflies, light is frequently associated with communication and reproduction. Males and females can use species-specific flashes to locate one another in darkness. Their glow can also function as a warning because many fireflies contain defensive chemicals that make them unpleasant or toxic to predators.
Click beetles have a different strategy.
Their steady glow may help make them appear dangerous or unappealing to predators. The light can also be particularly striking when the insect is flying through the darkness.
For a predator looking for a small meal, a glowing insect is a strange proposition: Is that food, or is it something I should leave alone?
Evolution has found many different ways to turn light into an advantage.
Some Are Almost Like Flying Headlights
One of the strangest things about Panama's glowing click beetles is the way their light can appear when they are flying.
The insect can have two luminous spots toward the rear of its thorax that look remarkably like tiny headlights. A separate light organ on the abdomen can become especially visible when the beetle takes flight.
Seeing one in the jungle can therefore be completely different from seeing a firefly.
A firefly might blink somewhere in the vegetation.
A click beetle can look like a tiny glowing machine moving through the darkness.
The Rainforest Is Not the Only Place to Look
You don't necessarily need to hike deep into untouched jungle to encounter bioluminescent insects.
They can occur in humid forest, along streams, around vegetation and in other suitable environments. A nighttime wildlife walk can dramatically increase the chances of seeing them because many of these insects are nocturnal.
Panama's Pipeline Road, for example, has produced observations of multiple bioluminescent insects during nighttime macro-photography walks.
The important thing is darkness.
The brighter the surroundings, the harder it is to appreciate tiny biological lights. A flashlight pointed directly at the forest can actually make these creatures easier to miss because your eyes become adapted to the artificial light rather than the faint glow coming from the vegetation.
This is one reason experienced night-walk guides often stop, switch off their lights and simply wait.
At first, there appears to be nothing.
Then your eyes adjust.
And suddenly the jungle starts glowing.
The Glowworms and Other Luminescent Creatures
There are also other groups of bioluminescent insects and insect relatives throughout the tropical world, including glowworm beetles, railroad worms and certain fungus gnats. Bioluminescence has evolved in several unrelated groups and can serve completely different purposes, including communication, defense and attracting prey.
This is one of the reasons nighttime rainforest exploration can be so surprising.
The little green light on a leaf isn't necessarily a firefly.
It could be a beetle.
It could be a larval stage.
It could belong to an entirely different group of organisms.
And identifying exactly what produced the glow can sometimes be much harder than simply spotting it.
A Chemical Flashlight With Almost No Heat
Bioluminescence is particularly impressive because it is extraordinarily efficient.
The insect is not burning something like a candle. Instead, specialized biological machinery produces light through chemistry. Luciferin reacts with oxygen under the action of luciferase, releasing energy in the form of visible light.
The result is sometimes called cold light because comparatively little energy is wasted as heat.
For an insect living in a hot tropical environment like Panama, that is an extraordinary adaptation.
The jungle can already be warm and humid enough without carrying around a tiny incandescent bulb.
A Jungle Full of Natural Light Shows
Perhaps the best way to appreciate Panama's glowing insects is to stop thinking of them as isolated curiosities.
At night, the rainforest becomes an enormous communication network.
Frogs call from streams.
Bats fly overhead.
Night birds move silently through the canopy.
Moths and other insects navigate through the darkness.
And scattered throughout the vegetation are tiny organisms producing their own light.
A firefly flashes.
Another responds.
A glowing click beetle crawls across a branch.
Somewhere else, another point of light appears.
The forest has not gone quiet or dark.
It has simply changed its language.
Turn Off the Flashlight
For anyone exploring Panama's jungle at night, one of the most memorable experiences can be surprisingly simple: turn off the flashlight.
Give your eyes a few minutes.
Don't move.
Look toward the ground, then the bushes, then the branches.
Eventually, the darkness begins to reveal things that were invisible moments earlier.
One green point becomes two.
Then five.
Then ten.
What initially looked like an ordinary tropical forest suddenly resembles a sky full of stars, except the stars are moving, flashing, crawling and flying only centimetres away.
And that is perhaps the most fascinating thing about Panama's glowing insects.
They don't need to be enormous, colorful or dangerous to be spectacular. Some of the jungle's most extraordinary nighttime wildlife is smaller than a fingernail and capable of producing its own light.
In a country where the rainforest is already famous for its biodiversity, these tiny living lanterns provide another reminder that Panama's wilderness doesn't simply come alive after dark.
It lights itself up.