Glow-worms and the night shift

The meadows around Parc Leopold settle into dusk with the last calls of wood pigeons fading from the ash trees. Night brings a different kind of activity to these Brussels wetlands, one that requires darkness to reveal itself. Step outside if you can. Let your eyes adjust to the growing shadows between the hedgerows.

In the grass beneath your feet, European glow-worms are beginning their ancient courtship. The females climb the tallest stems they can find, positioning themselves like tiny lighthouses in the vegetation. Each one carries a chemical lantern in her abdomen, mixing luciferin and luciferase with oxygen to produce a cold green light. No heat escapes this process. The energy goes entirely into illumination, a beacon that can shine for hours without burning the insect that makes it.

The males patrol the darkness, their large eyes scanning for these pinpricks of bioluminescence. They are smaller than the females, built for flight rather than light production. Their compound eyes contain thousands of individual lenses, each one capable of detecting the faintest glow from thirty feet away. When a male spots a female's light, he lands nearby and begins his approach. The female can control her beacon, dimming it or brightening it as potential mates draw closer. She evaluates each suitor, and only the most persistent will earn the chance to mate. This threatened species depends entirely on this light-based conversation, conducted in a language older than human settlements in these wetlands. The females need tall, undisturbed grass to position their lights effectively. The males require corridors of darkness to navigate between glowing signals. Modern lighting disrupts both needs, washing out the subtle communications that have evolved over millions of breeding seasons.

Other night hunters move through this same darkness. Bats patrol the airspace above the glow-worms, following echolocation maps that reveal flying insects invisible to human eyes. The invasive Asian lady beetles cluster beneath bark and stones, waiting for dawn to resume their hunt for aphids. Native ground beetles emerge from day roosts to hunt smaller prey along the soil surface. Each species has claimed a different layer of the night, dividing the darkness like territories on a map. The glow-worms occupy the narrow zone between ground and canopy, their lights threading through grass stems and low shrubs where their signals can travel farthest.

Close your eyes and listen to the night settling around you. The temperature drops with the sun, and moisture begins to gather on the grass blades. Somewhere in the darkness nearby, if you are still and patient, you might catch the faintest green glow moving slowly up a stem, a female glow-worm climbing toward her spotlight moment in the Brussels night.