Thanks all of you for concernig this intriguing me question. Though O. antiqua seems to be most common in Europe, I'd met it first time and was astonished by its beauty. From Buszko, Nowacki 2010 distributional check list it results that it is a bit rarer in Silesian Voivodeship, than in the surrounding ones.
Felipe is right. It is a common but not frequent European species. I used to find it on my pear tree. It is a bit similar to a centurio’s helmet decoration.
It may be Orgyia.https://warehouse1.indicia.org.uk/upload/Vapourer%20Moth,%20(Orgyia%20antiqua)%20Caterpillar%20Near%20Granitethorpe%20Quarry%20Sapcote%20SP%204960%209360%20(taken%2028.6.2009),,_caterpillar.2009),,.JPG