You won’t believe what these tiny creatures can do after dark

One photographer captures nature’s ultimate glow-up—the stunning ways animals fluoresce at night.

A bright blue scorpion sits on a tree branch with a dark sky and shrubbery in the background.
Lit by an ultraviolet flashlight, this common yellow scorpion shines bright cyan against the rusty night skies of Madrid, Spain.
Photographs byJavier Aznar González de Rueda
Text byCara Giaimo
Published March 19, 2026

The sight of a scorpion might make some people nervous, but Javier Aznar González de Rueda sees only a perfect muse for his camera. The Madrid-based photographer has spent years documenting bugs that shine—and virtually all scorpions fluoresce when exposed to ultraviolet light because of special substances in their exoskeletons that react to high-energy rays. Fluorescence is widespread in insects and arachnids. Why that’s the case, though, is a mystery. Scientists have hypotheses: It might help with camouflage, signaling to mates, or sun protection. But hard evidence is scarce.

During night walks, Aznar scouts for his multi-legged models, scanning the ground with a UV flashlight for telltale pops of neon. To get the best shots, he modified a pair of off-camera flashes to emit UV light, which, he says, “shows us the world in a different way.” The resulting portraits reveal what’s hidden: dun-colored scorpions glowing aquamarine, caterpillars with soft hairs, and insects with bright spots that match their surroundings. Aznar hopes his images will inspire more research into the role fluorescence plays in nature. Already, they’re showing a side of these creatures we’d never see otherwise.

A caterpillar glows bright blue and green with long hairs extending from its body.
The delicate hairs of this caterpillar, captured in Ecuador’s Yasuní National Park, roughly 150 miles from Quito, may signal to predators “Don’t eat me,” says photographer Javier Aznar González de Rueda.
A mantis is spotted with bright blue, red, and green marks and stands on top of a leaf with bright red dots.
Fluorescing lichens growing on a leaf in the Chocó rainforest near La Maná, Ecuador, have also made a home on this shield mantis. They create an extra layer of camouflage for the six-legged predator.
A bright blue katydid is perched on a yellow flower.
Caught by Aznar’s ultraviolet flash in Yasuní, this katydid shines vivid blue as it clambers atop a fleshy yellow flower.
Five caterpillars that are bright green with blue lines sit onto of a leaf with visible bright blue lines.
These spectacular neon green moth caterpillars, huddled on the underside of a leaf in Yasuní, have filaments that take on a deep-blue hue under UV light.
A wasp nest shows as a shiny blue with dark wasps crawling around it and is in front of a dark purple leaf.
Scientists aren’t sure if fluorescence, seen in this gleaming wasp’s nest, is meant to camouflage or to capture attention. Aznar’s images make a captivating argument for the latter.
A blue spider sits right beneath an orb glowing bright orange and red.
A spiny orb weaver spider spins an egg sac, the lacy pattern on her abdomen glowing from fluorophores—fluorescent molecules in the exoskeleton.
This story appears in the April 2026 issue of National Geographic magazine.