Dear Jeroen Voogd,
thank you very much for your photos. They are an enrichment to our Bestimmungshilfe. Unfortunately there are several villages called "Winterberg" in Germany. Can you please tell me: which Winterberg do you mean?
The caterpillars were found on March 26th 2017. Are the photos taken at this date, too?
Annette von Scholley-Pfab