We are lucky. "Four days ago the first males hatched", Adi Geyer greets us happily on a day at the end of June. One, two, four: like little paper planes, the white moths glide down the cliff face with wings spread out in a V-shape, patrol to the right and left and inspect everything that is white. After all, it could be a female willing to mate. "A few years ago I dropped a handkerchief and several males jumped on it," says the tall biologist.

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