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Catocala nupta
Noctuidae, Catocalinae, Catacalo nupta, Red Underwing:
ttp://www.lepiforum.de/cgi-bin/lepiwiki.pl?Catocala_Nupta
Ilia is an US species and not found in Poland. Polish ones are Catocala pacta (rare and critically endangered!) and Catocala sponsa, which both looks different.
looks like one I spotted in Utah
http://www.projectnoah.org/spottings/711...
Looks just like an ilia underwing to me, but I don't know whether those live in Poland.