Above all, we choose moonless nights, without rain and if possible with mild temperatures. This year, the nights of February were particularly unfavorable. We decided to start the inventory in March. But no, you're not dreaming, there are many butterflies in the cold winter nights!

And then, you need a very specific material. It is a cube whose faces are covered with a mosquito net allowing light to pass through. Each is pierced in the manner of louvers through which butterflies can enter but difficult to get out. To attract them into this cube, UV lamps are placed inside, powered by a battery. The trap is positioned in a clear place and left for the night. In the morning, before the sunrise, the butterflies are inspected one by one and photographed. The images obtained serve as a reminder for the dozens of species attracted and may be submitted to the opinion of colleagues in the case of difficult identification species. The butterflies are then released.