Vuurvliegjes / glimwormen

Lights in the dark

In the second half of June and the first weeks of July, they appear along the forest edges of the Ardennes and Belgian Limburg: fireflies. Or rather glow-worms, because it is almost always the females of Lampyris noctiluca that you see. They lie on the ground or in low vegetation, producing a cool, greenish light to attract males. That light lasts only a few weeks. You have a narrow window.

The best evenings are those just after a mild, slightly damp day, with no wind and well away from artificial light. Arrive after 22:00. Your eyes need to be fully adjusted to the dark before you will spot them. Walk quietly along the forest edge and look low. Sometimes you see one, sometimes dozens within a few metres of each other. It varies considerably from place to place and from year to year.

Composition and visual approach

There are two ways to work here. With a macro lens you can make close-ups of the female herself. They are small, around two centimetres, but the light organ is clearly visible through a macro lens on a tripod. Use a red-light torch to focus, as it interferes least with your exposure settings and keeps your own night vision intact.

The other approach is more landscape-oriented: a longer shutter speed of thirty seconds or more, letting several lights together form a pattern in the frame. A dark forest edge as a backdrop works better than an open field. ISO 1600 to 3200, a fast lens at f/2.8 or wider. Experiment with the shutter speed to decide how much movement you want to capture.

Practical matters

There is no single spot that works for everyone. Forest edges along unpaved tracks in the Ardennes, around Dinant or in the Hautes Fagnes, are promising areas. Belgian Limburg, towards the Hageland and the Voerstreek, too. You will rarely find them in manicured gardens or intensively managed woodland. Look for old, rough edges with plenty of moss and leaf litter.

Bring boots, as the ground is often damp. Do not drive along the forest edge with your headlights on when you arrive, it disturbs the animals. Park further away and walk in. And check sightings via Natuurpunt or waarnemingen.be for recent records in your search area beforehand. It can save you a wasted evening.

Season and expectations

The season is short. Late June is often the peak, but that depends on temperatures in the preceding weeks. A cold May pushes everything back. A warm June brings it forward. Go on several evenings if you can. The first time is all about searching. The second time, you already know where to stand.

Sources and further reading

• Natuurpunt
• Waarnemingen.be
• Natagora (natuur in Wallonië)
• Wikipedia: Lampyris noctiluca