This 2018 video from Germany is about large tortoiseshell butterflies.
This species had become extinct in the Netherlands. In 1996, a caterpillar was found for the last time. From 2011-2014 many adult butterflies were seen; but caterpillars only three times from 2000-2018.
This year, caterpillars were discovered at six different spots all over the Netherlands.
Scarce tortoiseshells, another species rare for the Netherlands, were also seen again this year.